Just started to sort out the V8 conversion recently (now that Winter is leaving)
and I have a "unique" problem with the cooling system. The details are:

Corvette (three core) Radiator;
Two Large Lexus puller fans (thermostatically set at 170 F)
Completely shrouded radiator system
Vented through the bottom of the front trunk
Coolant line under the vehicle are 1" I.D. thick wall aluminum tubing
Rod Simpson Water Pump (modified inlet; grafted GM thermostat housing)
Engine is a Late Model Chevy LT1 with external thermostat housing
Thermostat is a 180 F unit; with three 1/8" drilled relief holes.
Also I have a pressure bypass coolant line from the closed side of the
thermostat to the inlet side of the water pump; just to make sure at start-up
I don't generate enough pressure to blow any hoses off the block/pump/etc.
The expansion tank is about two litre capacity and is mounted high in the engine
bay on ther passenger side; on the inlet side of the water pump.
Next to the expansion tank is an overflow/recovery tank that allows coolant to
be retained from the other tank, when engine cools it get sucked back into the
expansion tank (all seems to be working properly; photo attached)
Radiator Cap has a 16 lbs. pressure rating

Otherwise the system works great and cools very well; just a blow by problem
as outline below:

At High Speed / RPM's the expansion tank overflows into the recovery tank
(I am assuming) THEN the recovery tank overflows and blows off coolant into the
atmosphere. (All the while the temperature guage remains constant at 180-190F)

I am thinking the Radiator Cap should be a higher rated pressure (maybe 20 lbs)?
the other problem could be I still have AIR in the system, does anyone know if
this is how the system might react with air ?

ANY thoughts or suggestions are appreciated. In the meantime I must keep my
foot out of the throttle until I sort this minor item; so so disappointing with this
little V8 sitting over my shoulder !!! Thanks again

Allan

Did you keep the cooling "reversed"? If so, did you keep the vent lines from the backs of the heads? What water pump are you running? Any chance of a head gasket problem?

i would assume the cooling system is no longer "reversed", as he is using a standard H2O pump, not an lt1 specific one.

A radiator cap is CHEAP. If you think it might fix it (or raise the effective limit, it is still not fixed)go for it.

Air in the system usaually shows it self in a fluctuating temp guage (cant read the temp of an air bubble) or a veryfast overheat (thermostat doesn't open due to the air not transfering the heat)

Plumbing the overflow into the water pump is different. i would look into that direction, wonder if where you are plumbing into might end up higher pressure than you anticipate.

Good luck
BJH

my guess would be that the flow to the radiator can't keep up with the water pump flow rate at high rpm,

Same problem I had.

Run a stronger cap. 18lb is what I think I have now. I wouldnt hesitate to run 20.


Throw away your old one and get a new one... I had a weak cap..

I use 2 16lb caps, one on the radiator and one in the back next to the engine, and overflow tanks at each location. I had a problem with the rear one leaking coolant easily. i replaced it with a new one of the same type and it seems to be fixed. But I run an electric waterpump mounted in the front by the radiator.
Pictures here http://pg.photos.yahoo.com/ph/nicksws6/alb...ksws6/my_photos

Gentlemen:

Bondo - as mentioned some time ago during our correspondence; since i am using the late model LT1 - I decided to engineer "backward"; dumped the
LT1 water pump; fabricated inlet/out adaptors for the engine block and Yes I did retain the reverse cooling. I also retained the vent line from the cylinder heads and connected it into the outlet coolant line going to the radiator. (Not sure why you asked about a head gasket problem; don't have or expect any problem !) The water pump I am running as previously mentioned is an older (modified) RSH unit which provides two outlets into the front of the block, and firstly goes to the cylinder heads (thus the reverse cooling) then from the heads through the block and exits the front of the block below the inlets. These outlets then go to the external thrmostat housing; before routed to the radiator.

Couple Additional Questions:

1/ On WHAT side of the coolant loop do most have theire Expansion Tank ?
(low pressure inlet side OR the higher pressure exdit side going to radiator)

2/ Does the Expansion tank need an Inlet AND Outlet ? (mine only has ONE hose)

Crazyhippy: what did you mean by "Plumbing the overflow into the water pump is different. i would look into that direction, wonder if where you are plumbing into might end up higher pressure than you anticipate." Can you be a little more specific ? (the overflow goes into a catch tank not the water pump; but the expansion tank is on the inlet (low pressure) side of the water pump)

3/ Where do most connect into the system for their water heater ?

Any other ideas, replies or comments would be appreciated. Thanks guys

Allan

I asked about a head gasket problem because that's a sure way to blow coolant out of an engine, BTDT.

I thought the vents from the back of the heads on an LT1 were supposed to go directly to the low pressure side of the pump. I know it allows some coolant to bypass the radiator, but I think preventing air pockets is more important. It's possible that you're getting hot spots in the heads and boiling some coolant, which would cause your problem.

Nick What gallon per minute is your water pump. Also what brand. I use an electric water pump Meizer and it flows 55gpm. I also mounted it at the bottom of the radiator, it will never run out of water there unless something major happens. Hc Cali 914.