My Renegade water pump failed yesterday. The pump impeller is stamped steel and the blades all just folded over or sheared off. I understand that the cast impellers are much stronger, but that not all manufacturer's cast models will fit into the Renegade housing. Anybody have experience with cast impeller pumps that will fit into the Renegade housing?
Since there is no bypass in the Renegade system, Renegade instructions are to limit the motor RPM to 3,000, or less, untill the thermostat opens. I have observed this, but the pump still failed after 5,500 miles. Renegade now makes a bypass kit, which I going to try, but I would still like to get a more durable pump.
Nick
Full Version: SBC V8 Water Pump Failure
some else just had this problem less than six months ago, search for it.
You run a Thermostat? I don't... but then again I dont have Heat in my car.
It's a mopar impeller, they make a few different styles. There was a thread on this recently....
A high volume thermostate had some bypass holes around the flange which permits a little flow that really helps dampen the opening and closing process during warm up and driving in different conditions.
A high volume thermostate had some bypass holes around the flange which permits a little flow that really helps dampen the opening and closing process during warm up and driving in different conditions.
I drilled a 1/16" hole in the flange of my t-stat in the Vette, but that's more for steam than any significant water flow.
It is hard to imagine that a pump would see sufficient backpressure in a system to flatten the stamped steel impellers. It would seem that the pump would cavitate before that happened. Just speculation.
If it's the same that was used some time ago, it is more than likely a GMB pump. The person that was making the stamped aftermarket impellers was making them out of some very weak material. There was a notch (indentation) in the blades to form somewhat of a gusset for strength.
The impellers could have been stamped from heavier gauge material, but then they wouldn't have been as inexpensive.
The only question as to whether the stock Big Block Chrysler impeller would fit is the depth of the impeller in the housing (the impeller thickness). A cast iron one could be made to the specifications, but one would have to order at least 300 pieces. There is to limited a market for that.
Alternatively, the stock cast iron one could more than likely be machined to appropriate dimensions.
All this is speculation, as we do not have a back housing to examine the fitment of a stock pump / impeller. Oh, and the original pump it was patterned after is fully cast iron. I posted an image of it in the previous thread about the same problem.
If it's the same that was used some time ago, it is more than likely a GMB pump. The person that was making the stamped aftermarket impellers was making them out of some very weak material. There was a notch (indentation) in the blades to form somewhat of a gusset for strength.
The impellers could have been stamped from heavier gauge material, but then they wouldn't have been as inexpensive.
The only question as to whether the stock Big Block Chrysler impeller would fit is the depth of the impeller in the housing (the impeller thickness). A cast iron one could be made to the specifications, but one would have to order at least 300 pieces. There is to limited a market for that.
Alternatively, the stock cast iron one could more than likely be machined to appropriate dimensions.
All this is speculation, as we do not have a back housing to examine the fitment of a stock pump / impeller. Oh, and the original pump it was patterned after is fully cast iron. I posted an image of it in the previous thread about the same problem.
Buy a Mopar Performance high flow water pump for a 383/440 big block. The High flow has cast impeller and is designed for big block engines with A/C. You can get them at Summit Racing.
This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.
I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.
I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.
Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.
Nick
QUOTE(nick mironov @ May 6 2010, 08:07 PM) 
This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.
I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.
I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.
Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.
Nick
look for the marine aplication. that would have the brass impeller. jegs and summit are your friend with hot rod parts [yes you have a hot rod].
QUOTE(nick mironov @ May 6 2010, 08:07 PM)
This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.
I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.
I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.
Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.
Nick
I've never heard of this problem before. I have thousnds of miles on mine without any problems. I used to own a big block Mopar. I'll see if I can track down an exact model number for you. Mopar pumps are cheap. If you go to your FLAPS and tell them you have a 1970 Charger 440 with A/C they can pull one and you can look at it. I have seen with Mopar engines the stamped pumps can corrode the impeller and lead to premature failure.
it's the cavitation that bends the impellers. cavitations generates a great amount of force
look here http://www.summitracing.com/search/Departm.../?Ns=Rank%7cAsc
look here http://www.summitracing.com/search/Departm.../?Ns=Rank%7cAsc
QUOTE(kg6dxn @ May 6 2010, 08:15 PM)
QUOTE(nick mironov @ May 6 2010, 08:07 PM)
This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.
I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.
I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.
Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.
Nick
I've never heard of this problem before. I have thousnds of miles on mine without any problems. I used to own a big block Mopar. I'll see if I can track down an exact model number for you. Mopar pumps are cheap. If you go to your FLAPS and tell them you have a 1970 Charger 440 with A/C they can pull one and you can look at it. I have seen with Mopar engines the stamped pumps can corrode the impeller and lead to premature failure.
Actually, this is the third SBC conversion that has had impeller failure in the last year: 1 Tony in WA, 2 drivability and 3 nick in SF.
Here's the best thread on the pumps that I've seen.
Yep I was one of those recient failures.
Click to view attachment
I went to the local AP store and tried to match up the crysler water pump with one in stock. one had too deep of impeller 6 blades, another had too large of a shaft blocking the rear inlet on the volute. I settled for a stamped 6 blade that seemed to fit and didnt block the inlet. for curiousity I stopped off at Shucks to see what they had. I found an 8 blade stamped steel with shallow blades that fit into the volute, not restricting the inlet. You can feel the outlet hoses " pressurize" when the enging is reved up. I almost question the hose sizing 7/8 supply to the rad, and 1-1/8 return to the pump.
fyi,I don't run a T-stat, I do wonder if I an over pressurizing the outlet, hoses swell when reved, but in all reality it is a circulating pump, as fluid moves out, the same volume returns to the inlet. No head required, the only restrictions are the block and radiator, if they both flow well, the return water to the pump should keep it from cavitating.
Well see if this one lasts or if the cast impeller is the way to go
Click to view attachment
I went to the local AP store and tried to match up the crysler water pump with one in stock. one had too deep of impeller 6 blades, another had too large of a shaft blocking the rear inlet on the volute. I settled for a stamped 6 blade that seemed to fit and didnt block the inlet. for curiousity I stopped off at Shucks to see what they had. I found an 8 blade stamped steel with shallow blades that fit into the volute, not restricting the inlet. You can feel the outlet hoses " pressurize" when the enging is reved up. I almost question the hose sizing 7/8 supply to the rad, and 1-1/8 return to the pump.
fyi,I don't run a T-stat, I do wonder if I an over pressurizing the outlet, hoses swell when reved, but in all reality it is a circulating pump, as fluid moves out, the same volume returns to the inlet. No head required, the only restrictions are the block and radiator, if they both flow well, the return water to the pump should keep it from cavitating.
Well see if this one lasts or if the cast impeller is the way to go
That failure looks exactly like mine...
The thread that was referenced in the previous reply was the thread that I found and it was informative. However, that thread does not have specifics on which manufacturer/model of a cast impeller pump will fit. It appears that Drive-Ability had to alter the housing to get his unidentified cast impeller pump to fit into the housing. There are lots of cast impeller pumps to be found on the web, but which ones actually fit?
Nick
The thread that was referenced in the previous reply was the thread that I found and it was informative. However, that thread does not have specifics on which manufacturer/model of a cast impeller pump will fit. It appears that Drive-Ability had to alter the housing to get his unidentified cast impeller pump to fit into the housing. There are lots of cast impeller pumps to be found on the web, but which ones actually fit?
Nick
maybe i will just keep running my stock water pump then.
In the other thread, someone asked what Ford did to prevent cavitation on their race engines. Ford redesigned the impeller to be a six curved blade, smaller diameter cast iron unit. They sold it for years in the Motorsports Division as a high performance impeller (to prevent cavitation at high rpms). Ford stopped making them so our GM had them cast and machined.
Like I said before, the minimum number of units is 300. So far that would leave us with 297 in stock if we did the Mopar units.
Like I said before, the minimum number of units is 300. So far that would leave us with 297 in stock if we did the Mopar units.
QUOTE(TC 914-8 @ May 6 2010, 10:44 PM)
Yep I was one of those recient failures.
Click to view attachment
I went to the local AP store and tried to match up the crysler water pump with one in stock. one had too deep of impeller 6 blades, another had too large of a shaft blocking the rear inlet on the volute. I settled for a stamped 6 blade that seemed to fit and didnt block the inlet. for curiousity I stopped off at Shucks to see what they had. I found an 8 blade stamped steel with shallow blades that fit into the volute, not restricting the inlet. You can feel the outlet hoses " pressurize" when the enging is reved up. I almost question the hose sizing 7/8 supply to the rad, and 1-1/8 return to the pump.
fyi,I don't run a T-stat, I do wonder if I an over pressurizing the outlet, hoses swell when reved, but in all reality it is a circulating pump, as fluid moves out, the same volume returns to the inlet. No head required, the only restrictions are the block and radiator, if they both flow well, the return water to the pump should keep it from cavitating.
Well see if this one lasts or if the cast impeller is the way to go
tony, nuke boomers cavitate thier props at 1500 feet, thats a lot of pressure and it still gets cavatation.
Here's the deal. I will send a pump (that was imaged) to whomever wants to try it in the housing. It would be the non-A/c pump. We can adjust the impeller depth if it is to deep.
The non-A/C pump has the larger diameter impeller.(4.185" - Pump # 1317). The A/C pump has the smaller diameter impeller (3.500" - Pump #1352). The stamped steel versions should have the same diameter and height as the cast iron impellers.
Gasket mounting surface to tip of impeller is 1.210" on both pumps. Gasket mounting surface to top of fan blade hub is 3.070" on both units.
And for the post that the shaft was to large in diameter, it could have been the big bearing model (don't remember the number now).
Anybody game? If it works, we can sell you the rebuilt proper OEM pump ... cast iron through and through (Shameless plug). Or, if you want the aluminum pump fitted with a cast iron impeller, that can be done too!
Please note that the bearing and seal would be destroyed with removal of the impeller, so the pump would have to be rebuilt as a new seal and bearing would have to be fitted).
The non-A/C pump has the larger diameter impeller.(4.185" - Pump # 1317). The A/C pump has the smaller diameter impeller (3.500" - Pump #1352). The stamped steel versions should have the same diameter and height as the cast iron impellers.
Gasket mounting surface to tip of impeller is 1.210" on both pumps. Gasket mounting surface to top of fan blade hub is 3.070" on both units.
And for the post that the shaft was to large in diameter, it could have been the big bearing model (don't remember the number now).
Anybody game? If it works, we can sell you the rebuilt proper OEM pump ... cast iron through and through (Shameless plug). Or, if you want the aluminum pump fitted with a cast iron impeller, that can be done too!
Please note that the bearing and seal would be destroyed with removal of the impeller, so the pump would have to be rebuilt as a new seal and bearing would have to be fitted).
I will take you up on this. My housing is out of the car now and I am waiting for the Renegade parts. I would rather have the cast impeller rather than the stamped steel impeller. Sending a PM...
Nick
Just find the right impeller assembly and replace it. i made a bypass for about $3 by running a 1/4" hose bypassing my hearer core, just enough to keep some water flowing.
40,000 pluis miles, no problems so far, but I am sure the pump wil go eventually, just like any other
Mark
40,000 pluis miles, no problems so far, but I am sure the pump wil go eventually, just like any other
Mark
This is the Test Setup.
Although the pump housing has two outlets, for convenience, I decided to use one for the pressure gauge and use the other for the output flow. If one were to test both outlets, I would not expect double the flow – maybe only 30% more. That would correspond well to the advertised pump rating of about 40 gpm at 4,000 RPM that I have seen.
Click to view attachment
The motive force for spinning the pumps during testing was a 2,500 RPM hand-drill attached to the protruding bolt on the blue-colored channel that you see in the picture. Unfortunately, the drill could not achieve the full 2,500 RPM under load, so I had to settle for whatever it could do. As a result I had to calculate the resulting water pressures at higher RPMs. The calculated results (list image) do seem to correspond to real conditions, indicating very high pressures at dead head conditions - thermostat is closed during cold engine conditions and not having a bypass. Note that a nearly closed thermostat could be experienced under cruise conditions in very mild weather resulting in the same high pressure effect. Based on my experience and many other posts that I have read about failed pump impellers, the high pressure conditions do happen and that’s what results in catastrophic pump failures.
The objective of this testing is to find a pump impeller that is more durable (able to withstand dead head pressures) and to possibly produce less pressure without sacrificing much water flow. Note that the Chrysler big block pumps were used on engines running at about 4,000 rpm, and in my case, my 283 SBC can run to over 6,000 rpm.
Although the pump housing has two outlets, for convenience, I decided to use one for the pressure gauge and use the other for the output flow. If one were to test both outlets, I would not expect double the flow – maybe only 30% more. That would correspond well to the advertised pump rating of about 40 gpm at 4,000 RPM that I have seen.
Click to view attachment
The motive force for spinning the pumps during testing was a 2,500 RPM hand-drill attached to the protruding bolt on the blue-colored channel that you see in the picture. Unfortunately, the drill could not achieve the full 2,500 RPM under load, so I had to settle for whatever it could do. As a result I had to calculate the resulting water pressures at higher RPMs. The calculated results (list image) do seem to correspond to real conditions, indicating very high pressures at dead head conditions - thermostat is closed during cold engine conditions and not having a bypass. Note that a nearly closed thermostat could be experienced under cruise conditions in very mild weather resulting in the same high pressure effect. Based on my experience and many other posts that I have read about failed pump impellers, the high pressure conditions do happen and that’s what results in catastrophic pump failures.
The objective of this testing is to find a pump impeller that is more durable (able to withstand dead head pressures) and to possibly produce less pressure without sacrificing much water flow. Note that the Chrysler big block pumps were used on engines running at about 4,000 rpm, and in my case, my 283 SBC can run to over 6,000 rpm.
This is the Lineup of the Tested Impellers.
Click to view attachment[
The first one is my failed impeller. I decided to test it just for yucks. It is missing one blade and I un-bent the others so it would at least spin without hitting anything in the housing. It actually worked surprisingly well (except for the violent out-of-balance vibration).
The second one is a brand new exact replacement stamped metal impeller with a 4.3” diameter (same as the damaged one).
The third one is a cast iron impeller with a 3.66” diameter and 6 blades. SLITS provided this rebuilt one to me for testing.
The fourth one is also cast iron impeller with a 4.365” diameter and 10 blades. SLITS also provided this rebuilt one to me for testing. Note that the 4.365” diameter is a tight fit into the 4.393: diameter housing.
Click to view attachment[
The first one is my failed impeller. I decided to test it just for yucks. It is missing one blade and I un-bent the others so it would at least spin without hitting anything in the housing. It actually worked surprisingly well (except for the violent out-of-balance vibration).
The second one is a brand new exact replacement stamped metal impeller with a 4.3” diameter (same as the damaged one).
The third one is a cast iron impeller with a 3.66” diameter and 6 blades. SLITS provided this rebuilt one to me for testing.
The fourth one is also cast iron impeller with a 4.365” diameter and 10 blades. SLITS also provided this rebuilt one to me for testing. Note that the 4.365” diameter is a tight fit into the 4.393: diameter housing.
Failed Stamped Impeller.
The impeller failed during simple city driving. I got about 5,000 miles out of it and never ran it about 3,000 RPM until the engine water temperature was above the thermostat 180 def F setting (per Renegade recommendations). The impeller failed anyway. I suspect that the blades bent a long time ago and finally one broke off, jamming the pump and leaving me stranded (not too far from home).
Click to view attachment
The impeller failed during simple city driving. I got about 5,000 miles out of it and never ran it about 3,000 RPM until the engine water temperature was above the thermostat 180 def F setting (per Renegade recommendations). The impeller failed anyway. I suspect that the blades bent a long time ago and finally one broke off, jamming the pump and leaving me stranded (not too far from home).
Click to view attachment
Replacement Stamped Impeller
This is an exact replacement of the failed pump. It fits easily into the housing and has lots of tip clearance. Notice that it is already rusting at the stress points.
Click to view attachment
This is an exact replacement of the failed pump. It fits easily into the housing and has lots of tip clearance. Notice that it is already rusting at the stress points.
Click to view attachment
3.66” Diameter Cast Impeller
This is the small diameter cast iron impeller that easily fits into the housing. SLITS says that this one is rated for engines with air conditioning. Odd that one would have a smaller impeller for that…
Note the very large hub. The concern was that the large hub would block the housing water inlet and result in very poor flow conditions and/or cavitation. From other posts that I have read, people seemed to have observed this condition and decided to abandon using this impeller. I decided to test it. I was also concerned that the smaller diameter would result in too little flow during idle conditions.
Click to view attachment
This is the small diameter cast iron impeller that easily fits into the housing. SLITS says that this one is rated for engines with air conditioning. Odd that one would have a smaller impeller for that…
Note the very large hub. The concern was that the large hub would block the housing water inlet and result in very poor flow conditions and/or cavitation. From other posts that I have read, people seemed to have observed this condition and decided to abandon using this impeller. I decided to test it. I was also concerned that the smaller diameter would result in too little flow during idle conditions.
Click to view attachment
4.365” Cast Impeller
I first thought that the impeller would not even fit into the housing. There was interference until I got it fully pressed in and bolted down. From other posts that I have read, people seemed to have tried to test-fit this kind of impeller (probably without fully installing it) and upon seeing the interference, also abandoned using it.
Click to view attachment
I first thought that the impeller would not even fit into the housing. There was interference until I got it fully pressed in and bolted down. From other posts that I have read, people seemed to have tried to test-fit this kind of impeller (probably without fully installing it) and upon seeing the interference, also abandoned using it.
Click to view attachment
Replacement Stamped Impeller in Housing
Note that there is lots of clearance at the housing inlet due to the open nature of this impeller.
Click to view attachment
Note that there is lots of clearance at the housing inlet due to the open nature of this impeller.
Click to view attachment
4.365” Cast Impeller in Housing
There is also good clearance at the housing inlet due to the relatively small hub.
Click to view attachment
There is also good clearance at the housing inlet due to the relatively small hub.
Click to view attachment
4.365” Cast Impeller in Housing
Note that there is only 0.006” clearance between the bottom of the blade tip and the housing (measures with a feeler gauge inserted into one of the outlets). The clearance between the blade and the housing is also very small (can’t really see it in this picture).
I would be very cautious about using this size impeller, because I would be concerned that any out of tolerance housing and/or impeller dimensions, bearing wear, etc. could lead to binding.
Click to view attachment
Note that there is only 0.006” clearance between the bottom of the blade tip and the housing (measures with a feeler gauge inserted into one of the outlets). The clearance between the blade and the housing is also very small (can’t really see it in this picture).
I would be very cautious about using this size impeller, because I would be concerned that any out of tolerance housing and/or impeller dimensions, bearing wear, etc. could lead to binding.
Click to view attachment
3.66” Cast Impeller in Housing
Note the very small clearance the large hub produces at the housing inlet. I thought that this would be very restrictive and cause flow problems. I was very surprised that it did not and the test results were very good.
Click to view attachment
Note the very small clearance the large hub produces at the housing inlet. I thought that this would be very restrictive and cause flow problems. I was very surprised that it did not and the test results were very good.
Click to view attachment
Housing
After I finished testing everything, I cleaned up the housing by buffing out the nicks and burrs, caused by the impeller failure, and beveled the inlet to get better inlet conditions.
Click to view attachment
After I finished testing everything, I cleaned up the housing by buffing out the nicks and burrs, caused by the impeller failure, and beveled the inlet to get better inlet conditions.
Click to view attachment
3.66” Cast Impeller in Housing after Beveling the Inlet.
The clearance was increased and the resulting clearance of about 0.25”, while it seems very small, is more than the net free area of the sum of the two outlets. I did not retest the 3.66” impeller after I did this, since it worked so well before beveling.
Click to view attachment
The clearance was increased and the resulting clearance of about 0.25”, while it seems very small, is more than the net free area of the sum of the two outlets. I did not retest the 3.66” impeller after I did this, since it worked so well before beveling.
Click to view attachment
The Results
Since I did not have test equipment to test the pumps at actual motor driven RPMs (idle through 6,000 RPM), I had to settle for low RPM tests and extrapolate out to the higher RPMs. The engine pulley and the pump pulley are the same size (they look the same, I didn’t actually measure them) so the pump RPM is the same as the engine RPM.
Since I could not achieve actual performance data, I decided to test only one of the two pump outlets for convenience. I think that if both outlets were testes simultaneously, the flow would not be double, but only about 30% more.
The results indicate relative (not absolute) performance of the pumps. See test data below.
Broken Stamped Impeller
This impeller, even though missing a blade and being mangled, performed surprisingly well (even though it was way out of balance). This means to me that one could have a badly damaged impeller with bent blades, and the pump would still work and one would never even know until a blade came off due to cyclic stressing.
Replacement Stamped Impeller
This produced the highest flows and pressures. However, highest flows and pressures are not necessarily what we want. We want to keep the pressures moderate so that we don’t burst the hoses or have the pump fail. Note that during dead head testing, the pressure was erratic and bouncing between 6 and 10 PSI. (The other pumps did not do this). This is suggesting to me that something like cavitation might be going on during dead heading. I suspect that this is what is causing the stamped pumps to fail.
3.66” Cast Impeller
This pump had the lowest pressure at only slightly reduced flow (even before I beveled the housing inlet). The idle flow was the lowest of the group (as expected), but not as low as I thought it would be. I settled on this pump and also beveled the inlet for better water flow. I did not retest it after beveling the inlet.
4.365” Cast Impeller
The tight tip clearance of this pump turned me off. Any small deviation could potentially cause it to bind up. It had good performance, better than the stamped impeller as far as pressure and flow. It was the best looking of (except that the hub appears to be out of round, but did not cause any noticeable vibration).
Other Information
I decided to install bypass anyway, to a keep the dead head pressures down. Renegade is starting to market a bypass system and I decided to try it. It is very simple. You remove the regular thermostat and install an external Wahler bypass thermostat, connect the discharge to the filler pot (as usual) and run the bypass back to the pump inlet and make the connection with a Tee fitting (pictures later). The Wahler thermostat is for a BMW 2002 or 320i. (W0133-1627641 80 deg C / 176 deg F, W0133-1627306 75 deg C / 167 deg F, W0133-1622197 71 def C / 160 deg F)
Cast Iron Pump Sources
Slits says that he has 30 cores (3.66 diameter cast iron) that can be rebuilt and sold for $55 plus shipping. This is a very good deal. Although I could find many kinds of stamped and cast impeller pumps on the internet, I could find no information about impeller diameters or any other specific dimensions. And, the designs from the various manufacturers are quite different. You would need to use trial and error to find what could fit into your housing. Judging from the pictures that I saw, the marine big block Chrysler pumps seem to have the smaller diameter. The cast iron impeller pumps that I saw ran in the $125 to $200 range. The stamped impeller pumps ran in the $30 to $90 range. My recommendation – go with SLITS.
Click to view attachment
Since I did not have test equipment to test the pumps at actual motor driven RPMs (idle through 6,000 RPM), I had to settle for low RPM tests and extrapolate out to the higher RPMs. The engine pulley and the pump pulley are the same size (they look the same, I didn’t actually measure them) so the pump RPM is the same as the engine RPM.
Since I could not achieve actual performance data, I decided to test only one of the two pump outlets for convenience. I think that if both outlets were testes simultaneously, the flow would not be double, but only about 30% more.
The results indicate relative (not absolute) performance of the pumps. See test data below.
Broken Stamped Impeller
This impeller, even though missing a blade and being mangled, performed surprisingly well (even though it was way out of balance). This means to me that one could have a badly damaged impeller with bent blades, and the pump would still work and one would never even know until a blade came off due to cyclic stressing.
Replacement Stamped Impeller
This produced the highest flows and pressures. However, highest flows and pressures are not necessarily what we want. We want to keep the pressures moderate so that we don’t burst the hoses or have the pump fail. Note that during dead head testing, the pressure was erratic and bouncing between 6 and 10 PSI. (The other pumps did not do this). This is suggesting to me that something like cavitation might be going on during dead heading. I suspect that this is what is causing the stamped pumps to fail.
3.66” Cast Impeller
This pump had the lowest pressure at only slightly reduced flow (even before I beveled the housing inlet). The idle flow was the lowest of the group (as expected), but not as low as I thought it would be. I settled on this pump and also beveled the inlet for better water flow. I did not retest it after beveling the inlet.
4.365” Cast Impeller
The tight tip clearance of this pump turned me off. Any small deviation could potentially cause it to bind up. It had good performance, better than the stamped impeller as far as pressure and flow. It was the best looking of (except that the hub appears to be out of round, but did not cause any noticeable vibration).
Other Information
I decided to install bypass anyway, to a keep the dead head pressures down. Renegade is starting to market a bypass system and I decided to try it. It is very simple. You remove the regular thermostat and install an external Wahler bypass thermostat, connect the discharge to the filler pot (as usual) and run the bypass back to the pump inlet and make the connection with a Tee fitting (pictures later). The Wahler thermostat is for a BMW 2002 or 320i. (W0133-1627641 80 deg C / 176 deg F, W0133-1627306 75 deg C / 167 deg F, W0133-1622197 71 def C / 160 deg F)
Cast Iron Pump Sources
Slits says that he has 30 cores (3.66 diameter cast iron) that can be rebuilt and sold for $55 plus shipping. This is a very good deal. Although I could find many kinds of stamped and cast impeller pumps on the internet, I could find no information about impeller diameters or any other specific dimensions. And, the designs from the various manufacturers are quite different. You would need to use trial and error to find what could fit into your housing. Judging from the pictures that I saw, the marine big block Chrysler pumps seem to have the smaller diameter. The cast iron impeller pumps that I saw ran in the $125 to $200 range. The stamped impeller pumps ran in the $30 to $90 range. My recommendation – go with SLITS.
Click to view attachment
Very nice. Thanks for doing the research for our benefit. I think I should buy one even though I don't need it yet.
Great write up, details and data.
When I was looking for a replacement pump after my failure, I came accross 2 stamped impellers, one 6-blade and one 8 blade., I went with the 8-blade, I do have concerns of overpressurizing my system at high RPM, my outlet hoses from the pump and the hose exiting the engine, swell like a ball park frank when reved up. I don't have a T-stat so dead heading shouldent be a problem. I would be curious on measuring the above pumps gpm and head and plotting a performance curve like OEM water circulating pumps, just a thought.
I'll keep your info handy, if my new 8 blade pump fails I'll be going with a cast type.
Good job,
Thanks,
T
When I was looking for a replacement pump after my failure, I came accross 2 stamped impellers, one 6-blade and one 8 blade., I went with the 8-blade, I do have concerns of overpressurizing my system at high RPM, my outlet hoses from the pump and the hose exiting the engine, swell like a ball park frank when reved up. I don't have a T-stat so dead heading shouldent be a problem. I would be curious on measuring the above pumps gpm and head and plotting a performance curve like OEM water circulating pumps, just a thought.
I'll keep your info handy, if my new 8 blade pump fails I'll be going with a cast type.
Good job,
Thanks,
T
I had a similar problem, I looked around and found a cast impeller. The unit wouldn't fit in the renegade housing. I ended up shaping the renegade housing with a sandpaper hone mounted on my drill press. It took some time and I did get the pump to fit. Works fine...
This is Scott using Steve's 914 World account for now...
First of all...I have seen the failures that are discussed in this thread. There are several reasons why the failures have increased over the years including lower quality parts used to build the impellers, higher RPM's due to better aftermarket engine technology, cheaper thermostats that don't flow enough volume when open, more debris and blockages in the ageing engine blocks, and just the fact that there are so many SBC 914's and 911's that have finally found the road...and not just a dark corner of the garage covered in dirty laundry and kids toys!
My little orange 914 from years back that some of you named "Peal", went through a few water pumps in it's day. I was stranded on a cold windy night on the long State Line grade with just such a failure...so I completely understand the frustration. BUT...it was the cast impeller/water pump that failed that time at the shaft seals and not the typical carnage with the impeller failures. That engine was frequently spun to 6800 RPM and was never driven easily I can assure you.
Where we saw the most consistent failures was with customers that revved the engine past about 2500 or 3000 RPM before the thermostat was open. Drilling two or three small holes in the T-stat was the easy way to relieve the pressure a little so the water pump would have a fighting chance. Often the pump would sustain damage after just such a high RPM rap of the throttle when cold, but it would still move some water. BUT, just like the paper clip, eventually the blades would give up and curl themselves around the shaft.
In an attempt to help our little water pumps to live longer, we developed an easy fix with a bi-pass T-stat design. Water temps have been consistent, water pump failures seem to be less, hose pressures have been more stable, no need to drill holes in the T-stat, heater core temps have increased on cold days, and it's easy to install.
In summary, keeping the RPM's down when your engine is cold, is a good idea in general and may help your water pump last. Installing the cast water pump was a solution I have tried, but they are not completely immune from failure. Different impeller designs will change flow rates that will effect your ability to cool. Using a good quality, high flow T-stat, with two or three small holes drilled, will work very well for this application. Flushing your block and cooling system completely will also increase flow and thermal transfer allowing the engine to cool more efficiently. Installing the new bi-pass system seems to be the next logical step if you are still having issues.
On our end, we have looked into impeller suppliers and we think we are using the lesser of all the evils. There is some really bad junk being made out there, but the ones we have are lasting when reasonable care is exercised.
If you have any further questions, you are welcome to call Steve or myself here at the shop. Thanks for all the good input here on 914 World without the drama that finds it's way into these boards from time to time. Keep up the good work!
Sincerely,
Scott >>> Renegade Hybrids
www.renegadehybrids.com
(866) 498-2421 toll free
First of all...I have seen the failures that are discussed in this thread. There are several reasons why the failures have increased over the years including lower quality parts used to build the impellers, higher RPM's due to better aftermarket engine technology, cheaper thermostats that don't flow enough volume when open, more debris and blockages in the ageing engine blocks, and just the fact that there are so many SBC 914's and 911's that have finally found the road...and not just a dark corner of the garage covered in dirty laundry and kids toys!
My little orange 914 from years back that some of you named "Peal", went through a few water pumps in it's day. I was stranded on a cold windy night on the long State Line grade with just such a failure...so I completely understand the frustration. BUT...it was the cast impeller/water pump that failed that time at the shaft seals and not the typical carnage with the impeller failures. That engine was frequently spun to 6800 RPM and was never driven easily I can assure you.
Where we saw the most consistent failures was with customers that revved the engine past about 2500 or 3000 RPM before the thermostat was open. Drilling two or three small holes in the T-stat was the easy way to relieve the pressure a little so the water pump would have a fighting chance. Often the pump would sustain damage after just such a high RPM rap of the throttle when cold, but it would still move some water. BUT, just like the paper clip, eventually the blades would give up and curl themselves around the shaft.
In an attempt to help our little water pumps to live longer, we developed an easy fix with a bi-pass T-stat design. Water temps have been consistent, water pump failures seem to be less, hose pressures have been more stable, no need to drill holes in the T-stat, heater core temps have increased on cold days, and it's easy to install.
In summary, keeping the RPM's down when your engine is cold, is a good idea in general and may help your water pump last. Installing the cast water pump was a solution I have tried, but they are not completely immune from failure. Different impeller designs will change flow rates that will effect your ability to cool. Using a good quality, high flow T-stat, with two or three small holes drilled, will work very well for this application. Flushing your block and cooling system completely will also increase flow and thermal transfer allowing the engine to cool more efficiently. Installing the new bi-pass system seems to be the next logical step if you are still having issues.
On our end, we have looked into impeller suppliers and we think we are using the lesser of all the evils. There is some really bad junk being made out there, but the ones we have are lasting when reasonable care is exercised.
If you have any further questions, you are welcome to call Steve or myself here at the shop. Thanks for all the good input here on 914 World without the drama that finds it's way into these boards from time to time. Keep up the good work!
Sincerely,
Scott >>> Renegade Hybrids
www.renegadehybrids.com
(866) 498-2421 toll free
I purchased Scott's / Renegade's bypass thermostat solution. Nice, neat solution. It installs fairly easily. The only problem was that the kit's Y-fitting for the bypass connection at the pump suction did not fit because of my particular setup (I have steel tubing under the car rather than hoses), so I made a T-fitting (pictures later).
It is now installed and the cooling system is "burped". The coolant seems to come up to temperature twice as fast as before, which is very nice (and unexpected). I will report on the results after some varied driving conditions.
Even though I strictily followed Renegade's 3,000 RPM limit when cold and had the holes drilled into the T'stat, the pump still failed, and while driving only 35 mph. The pressure bounce (see results above) of the stamped impeller test suggests that there is some significant cyclic pressure effect for that impeller style. I suspect that it is this cyclic pressure variation that ultimately makes the blades fail from bending fatigue (just like bending and breaking a paper clip). The cast pumps did not exhibit this condition, so it must be something about the geometry of the stamped impeller. My guess is that if you open up your pump housing your blades will already be bent, and it is only a matter of time before one fails and breaks off. Note that the test of the broken pump (one blade missing altogether and 5 remaining bent blades still moved water pretty well. One would not suspect a problem until it was too late.
In any case, a bypass is the way to go, and the Renegade kit is very simple. I am further hedging my bets and using Slits's cast impeller with the Renegade bypass kit.
Nick
It is now installed and the cooling system is "burped". The coolant seems to come up to temperature twice as fast as before, which is very nice (and unexpected). I will report on the results after some varied driving conditions.
Even though I strictily followed Renegade's 3,000 RPM limit when cold and had the holes drilled into the T'stat, the pump still failed, and while driving only 35 mph. The pressure bounce (see results above) of the stamped impeller test suggests that there is some significant cyclic pressure effect for that impeller style. I suspect that it is this cyclic pressure variation that ultimately makes the blades fail from bending fatigue (just like bending and breaking a paper clip). The cast pumps did not exhibit this condition, so it must be something about the geometry of the stamped impeller. My guess is that if you open up your pump housing your blades will already be bent, and it is only a matter of time before one fails and breaks off. Note that the test of the broken pump (one blade missing altogether and 5 remaining bent blades still moved water pretty well. One would not suspect a problem until it was too late.
In any case, a bypass is the way to go, and the Renegade kit is very simple. I am further hedging my bets and using Slits's cast impeller with the Renegade bypass kit.
Nick
Ok, last bit of information I will post on this.
First, the GMB pump is the cheapest piece of crap on the market. Rebuilders will not touch their castings as the metallurgy, QC and such is just to shabby for a reliable rebuild. Secondly, they use cermaic seals which can crack and leak at the blink of an eye if subjected to cavitation.
I won't address the poor quality of the stamped steel impellers. The buying public demands inexpensive and that's exactly what they get.
As far as the seals / bearings going out ... The seals on a water pump were designed as a secondary pressure outlet. If the thermostat doesn't open on excess pressure, the seal will and weep water. If it is leaking, something else is wrong in the system.
Bearings will fail due to excess tension on the pulley. Remember, that pulley is side-loaded (kinda like spacing rims out causes wheel bearing failure) and that is why the manufacturers specify a specific tension.
As I was told, a water pump can be built to never leak, but was designed the way as they are as a secondary pressure relief in the system (just like freeze plugs, etc).
Be aware, all pumps can have their problems, but the impeller blades of a cast iron pump do not bend nor disintegrate (unless you don't renew your coolant) Coolant (ethylene glycohol or even propolyene glycohol) breaks down into two organic acids under heat. These acids go after system metals and especially like aluminum.
You can choose whichever pump you wish. All this thread has done is expose exactly what the pumps are. I am not the expert here ... the gentleman I ask questions of has 40 years in the water pump rebuilding industry.
First, the GMB pump is the cheapest piece of crap on the market. Rebuilders will not touch their castings as the metallurgy, QC and such is just to shabby for a reliable rebuild. Secondly, they use cermaic seals which can crack and leak at the blink of an eye if subjected to cavitation.
I won't address the poor quality of the stamped steel impellers. The buying public demands inexpensive and that's exactly what they get.
As far as the seals / bearings going out ... The seals on a water pump were designed as a secondary pressure outlet. If the thermostat doesn't open on excess pressure, the seal will and weep water. If it is leaking, something else is wrong in the system.
Bearings will fail due to excess tension on the pulley. Remember, that pulley is side-loaded (kinda like spacing rims out causes wheel bearing failure) and that is why the manufacturers specify a specific tension.
As I was told, a water pump can be built to never leak, but was designed the way as they are as a secondary pressure relief in the system (just like freeze plugs, etc).
Be aware, all pumps can have their problems, but the impeller blades of a cast iron pump do not bend nor disintegrate (unless you don't renew your coolant) Coolant (ethylene glycohol or even propolyene glycohol) breaks down into two organic acids under heat. These acids go after system metals and especially like aluminum.
You can choose whichever pump you wish. All this thread has done is expose exactly what the pumps are. I am not the expert here ... the gentleman I ask questions of has 40 years in the water pump rebuilding industry.
The Renegade system thermostat with bypass is now installed and operating.
The Wahler thermostat is for a BMW 2002 or 320i. (W0133-1627641 80 deg C / 176 deg F, W0133-1627306 75 deg C / 167 deg F, W0133-1622197 71 def C / 160 deg F)
The thermostat installation is pretty tight at the rear firewall, especially if you still have the acoustic pad. You could probably come up with a different water outlet that will give you more room.
The system vented fairly easily and was pretty mcuh free of air after 3 or 4 runs.
The coolant warms up to operating temperature twice as fast as before. I didn't expect this at all. It must be because the small holes I drilled into the original thermostat for promoting venting and some flow during cold conditions let through some water which ran through the radiator and was cooled. Anyway - a benefit.
Everything works as expected, but we have not had any really warm weather to give the bypass thermostat and new water pump a serious test.
Click to view attachment
The Wahler thermostat is for a BMW 2002 or 320i. (W0133-1627641 80 deg C / 176 deg F, W0133-1627306 75 deg C / 167 deg F, W0133-1622197 71 def C / 160 deg F)
The thermostat installation is pretty tight at the rear firewall, especially if you still have the acoustic pad. You could probably come up with a different water outlet that will give you more room.
The system vented fairly easily and was pretty mcuh free of air after 3 or 4 runs.
The coolant warms up to operating temperature twice as fast as before. I didn't expect this at all. It must be because the small holes I drilled into the original thermostat for promoting venting and some flow during cold conditions let through some water which ran through the radiator and was cooled. Anyway - a benefit.
Everything works as expected, but we have not had any really warm weather to give the bypass thermostat and new water pump a serious test.
Click to view attachment
The only problem I had was that the Renegade "Y" fittinng would not fit into the space I had available (probably because I have pipe inder the car instead of hoses). So, I soldered together a 1" copper "T" fitting and got the exact angles I needed so that the hoses were not kinked.
Click to view attachment
Click to view attachment
First let me say that I have never done a SBC conversion. I have however had a lot of SBC experience. If I am covering something that has already been looked at, forgive me.....
On a stock Chevy block at the water pump there is a bypass port above the bolt holes on the inlet side of the water pump and the gasket has a hole in it for the port.
The port allows full circular flow around the engine and a fast warm up. Pressure pushes through the block and it pushes out the bypass port to be circulated by the water pump again. In essence keeping hot spots down and allowing the engine water to uniformly warm up as it flows in a circle. If that hole is blocked off, the water will not have any place to go, will not circulate and would cause problems that you guys are describing.
Has anyone drilled a hole at the cover plate at the bypass hole and plumbed that to the inlet of the remote water pump to allow full circulation? Ya can't have a pump discharge to nowhere without a problem.
The above pictures of bypass seems to do similar but quite large for the requirement.
On a stock Chevy block at the water pump there is a bypass port above the bolt holes on the inlet side of the water pump and the gasket has a hole in it for the port.
The port allows full circular flow around the engine and a fast warm up. Pressure pushes through the block and it pushes out the bypass port to be circulated by the water pump again. In essence keeping hot spots down and allowing the engine water to uniformly warm up as it flows in a circle. If that hole is blocked off, the water will not have any place to go, will not circulate and would cause problems that you guys are describing.
Has anyone drilled a hole at the cover plate at the bypass hole and plumbed that to the inlet of the remote water pump to allow full circulation? Ya can't have a pump discharge to nowhere without a problem.
The above pictures of bypass seems to do similar but quite large for the requirement.
QUOTE(nick mironov @ May 26 2010, 10:00 AM)
This is the Test Setup.
Although the pump housing has two outlets, for convenience, I decided to use one for the pressure gauge and use the other for the output flow. If one were to test both outlets, I would not expect double the flow – maybe only 30% more. That would correspond well to the advertised pump rating of about 40 gpm at 4,000 RPM that I have seen.
Click to view attachment
The motive force for spinning the pumps during testing was a 2,500 RPM hand-drill attached to the protruding bolt on the blue-colored channel that you see in the picture. Unfortunately, the drill could not achieve the full 2,500 RPM under load, so I had to settle for whatever it could do. As a result I had to calculate the resulting water pressures at higher RPMs. The calculated results (list image) do seem to correspond to real conditions, indicating very high pressures at dead head conditions - thermostat is closed during cold engine conditions and not having a bypass. Note that a nearly closed thermostat could be experienced under cruise conditions in very mild weather resulting in the same high pressure effect. Based on my experience and many other posts that I have read about failed pump impellers, the high pressure conditions do happen and that’s what results in catastrophic pump failures.
The objective of this testing is to find a pump impeller that is more durable (able to withstand dead head pressures) and to possibly produce less pressure without sacrificing much water flow. Note that the Chrysler big block pumps were used on engines running at about 4,000 rpm, and in my case, my 283 SBC can run to over 6,000 rpm.
Hey Nick,
Not quite to the point where I have experienced a water pump failure... but great info non-the-less!
I have a few questions pertaining to the installation/configuration of the 2 water pump hoses and where they attach to the engine block. I think you answered one of the questions already with your photo... just need confirmation!
Specifically, I am using a Renegade mechanical water pump setup (mounted on the drivers side) and I've seen some conflicting photos of how the two smaller water pump ports are connected to the front of the block(SBC)... in regards to which port on the water pump gets connected to which port on the front side of the engine? Does it matter?
It seems like the water pump can be mounted in its bracket in more than one position. I think the whole pump can be rotated 90 degrees at a time until the pump to bracket bolts line up. Does this matter?
At this moment, mine is mounted so that, looking at the rear of the pump, one small port is at the 10-11 o'clock position and the other is at the 4-5 o'clock position. The inlet port on the water pump (coming from the radiator) is facing down or at the 6 o'clock position. Is this okay?
Once again, any info is greatly appreciated.
Thanks again!
Tony
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