Full Version: Setting deck height for 9:1 compression
No kidding. I think it would be fun to try and build something like that. I wonder what boost and compression look like.
That 2110cc type 1 engine was built by Sid Collins of Troysport of Orlando. He is retired now, but he was the MAN in this area for 40 years. He also kicked ass at Sebring in a little red 356 for decades. I had that engine built back in 1997 and it’s still sitting on my shelf in the garage filled to the brim with oil. I built the engine originally in 1989 but could never get the turbo to come on early enough to make it drivable. It would bog down horribly and then come on too hard to control around 2800 rpm’s. It went to a couple local shops in Indiana where it sat for over 2 years with no success. I then moved to Florida in 1992 and brought it with me because it was my first car and love. I was hit by a truck on my GSXR in 95 and it pretty much totaled me. I was bed ridden for over a year and then it took me 5 years to learn how to walk. In that time I used to go to my friend Scott’s cylinder head shop where he did custom porting work for Sid on his 356 race car. Over time Sid and I became friends and he offered to get the big engine sorted out for me. He told me it wouldn’t be done in a hurry but it would be right. 2 years later he called me and told me to come hear it run on the water dyno. It sounded so good and came on smoothly through the power range. He laughed and said, it might run for years, or it might grenade on the first pass down the track…lol. It has never made it back into the car. The superbettle body was perfect when I brought it to Fl but sitting in 100% humidity in a field for 10 years rotted it out badly. I have replace all floors and lower sheet metal in the past few years and it’s coming along slowly because as I said ….project disease!!!
As far as I remember…. Forged internals SCAT ( only thing that existed back then)
Rajay turbo feed by progressive 2 barrel
And then whatever Sid the guru did after he tore it all apart and
did his magic. I know he made custom pushrods because he said
my geometry was off. I didn’t understand any of that back in the
early days. I’ll try to find some picture in the next few days and
post them. I’ll uncover the engine as well and snap a few pics.
As far as I remember…. Forged internals SCAT ( only thing that existed back then)
Rajay turbo feed by progressive 2 barrel
And then whatever Sid the guru did after he tore it all apart and
did his magic. I know he made custom pushrods because he said
my geometry was off. I didn’t understand any of that back in the
early days. I’ll try to find some picture in the next few days and
post them. I’ll uncover the engine as well and snap a few pics.
I did do a deep dive into turbo T4s after seeing your turbo T1 notes.
There is also another old thread that re-surface showing a baby system on a 1.7 that seems to "work" but at low levels (7-8 psi)
Lenn Hoffman set me straight!
He suggested a single 1.7 head casting (Q?) was the way to go and high boost would make the combustion chamber besides/below the exhaust port "droop", loosen up the valve seat, and "The Reaper" would arrive shortly thereafter...
There was also a long discussion on using some very special T4 heads that had side exit exhaust (like a T1!). Looks like these critters were 4-5K for a pair a decade ago.
These REQUIRED the DTM cooling system (like a T1 as well).
I saw enough to answer my "Hey, maybe boost is The Way" thoughts.
Nope.
No "blowing" a T4 in my future!
Water boxer Porsche 6 or GM LGX will be my path...
There is also another old thread that re-surface showing a baby system on a 1.7 that seems to "work" but at low levels (7-8 psi)
Lenn Hoffman set me straight!
He suggested a single 1.7 head casting (Q?) was the way to go and high boost would make the combustion chamber besides/below the exhaust port "droop", loosen up the valve seat, and "The Reaper" would arrive shortly thereafter...
There was also a long discussion on using some very special T4 heads that had side exit exhaust (like a T1!). Looks like these critters were 4-5K for a pair a decade ago.
These REQUIRED the DTM cooling system (like a T1 as well).
I saw enough to answer my "Hey, maybe boost is The Way" thoughts.
Nope.
No "blowing" a T4 in my future!
Water boxer Porsche 6 or GM LGX will be my path...
I do remember that my boost exhaust gate was set at 6psi
Yeah like I said….may last a long time or grenade on the first track day…lol
Yeah like I said….may last a long time or grenade on the first track day…lol
Chad, I wouldn't spec a "draw through" turbo system on ANYTHING today.
Lots of pitfalls...
I wouldn't spec a "Blow Through" on carbs either.
One of my Mentors is Corky Bell.
I worked for him in the early 80s and he WAS doing blow throughs then.
He's dropped "draw throughs" years ago at that point.
Mikunis were Corky's go to carbs for forced induction, and they SPEW fuel everywhere past 14psi.
He did an intercooled blow through Mukuni on the first gen RX7 that took 100hp to 285!
Rotary is more like a 2 stroke than a 4 and they really like boost!
The Rotary engine is not robust enough IMO for long life under boost.
A mild system is below 15psi now. This was the upper limit back in 83 with all sorts of fuel systems mods, some of which didn't work very well.
A serious system goes 20+, some hit 30 today!
Digital FI. Injectors pointed at intake valves. Good intercooling, Flex fuel (E/85).
Modern turbo (the aerodynamics of the internals has changed BIGTIME over that Rayjay). COP ignition. Piston squirters.
The above is the "standard" recipe today.
The stand-alone digital FI MADE modern turbocharging possible!
Lots of pitfalls...
I wouldn't spec a "Blow Through" on carbs either.
One of my Mentors is Corky Bell.
I worked for him in the early 80s and he WAS doing blow throughs then.
He's dropped "draw throughs" years ago at that point.
Mikunis were Corky's go to carbs for forced induction, and they SPEW fuel everywhere past 14psi.
He did an intercooled blow through Mukuni on the first gen RX7 that took 100hp to 285!
Rotary is more like a 2 stroke than a 4 and they really like boost!
The Rotary engine is not robust enough IMO for long life under boost.
A mild system is below 15psi now. This was the upper limit back in 83 with all sorts of fuel systems mods, some of which didn't work very well.
A serious system goes 20+, some hit 30 today!
Digital FI. Injectors pointed at intake valves. Good intercooling, Flex fuel (E/85).
Modern turbo (the aerodynamics of the internals has changed BIGTIME over that Rayjay). COP ignition. Piston squirters.
The above is the "standard" recipe today.
The stand-alone digital FI MADE modern turbocharging possible!
Ok….
Everything is back together after the deck was machined .010 and the heads were fly cut approx .030 to get my head cc total down to my desired 57cc with the valve relief figured into the equation. And yes they also cut .030 off of the ridge on the flat surface of the head so that it would seat fully down onto the cylinder. After assembling the cylinders and pistons without shims, my deck heights varied from—
.035 to .033 on cylinders #1 and #2
.041 to .035 on cylinders #3 and #4
I performed the measurements with a level and feeler gauges at the center of the piston, parallel to the pin. I then repeated the same test with my digital depth gauge magnetized to a steel mounted plate.
I then disassembled the pistons and cylinders and did the exact same tests, using the same piston and cylinder on all 4 different registers. The test shows the exact same results, so that should mean that the pistons and cylinders are equal in distance. This leaves me to think that the new forged rods I purchased must have some discrepancies in their length. Along with bearing differences as well added in there. The rods were supposedly checked and balanced by the seller. I did weight match all my rods and they were within .02 grams of each other.
From my research over the past few days I have found this is not uncommon. Just want to get the best path forward to achieve an engine that will perform and hopefully last.
I know there has to be an acceptable tolerance from head to head so that it will seal properly. And I’m sure there is an acceptable tolerance from one side of the case to the other.
In my head I am reasoning that if I shim one cylinder and not the other to correct the total deck height, it will then make the cylinder head rock on the uneven cylinders since they are all the same height.
So what is my best path forward?
Thanks again for your patience and time….Chad
Everything is back together after the deck was machined .010 and the heads were fly cut approx .030 to get my head cc total down to my desired 57cc with the valve relief figured into the equation. And yes they also cut .030 off of the ridge on the flat surface of the head so that it would seat fully down onto the cylinder. After assembling the cylinders and pistons without shims, my deck heights varied from—
.035 to .033 on cylinders #1 and #2
.041 to .035 on cylinders #3 and #4
I performed the measurements with a level and feeler gauges at the center of the piston, parallel to the pin. I then repeated the same test with my digital depth gauge magnetized to a steel mounted plate.
I then disassembled the pistons and cylinders and did the exact same tests, using the same piston and cylinder on all 4 different registers. The test shows the exact same results, so that should mean that the pistons and cylinders are equal in distance. This leaves me to think that the new forged rods I purchased must have some discrepancies in their length. Along with bearing differences as well added in there. The rods were supposedly checked and balanced by the seller. I did weight match all my rods and they were within .02 grams of each other.
From my research over the past few days I have found this is not uncommon. Just want to get the best path forward to achieve an engine that will perform and hopefully last.
I know there has to be an acceptable tolerance from head to head so that it will seal properly. And I’m sure there is an acceptable tolerance from one side of the case to the other.
In my head I am reasoning that if I shim one cylinder and not the other to correct the total deck height, it will then make the cylinder head rock on the uneven cylinders since they are all the same height.
So what is my best path forward?
Thanks again for your patience and time….Chad
On a single bank the jugs have to be level with each other!
The .002" range difference between 1-2-4 I'd live with.
#3 at .041" I'd "fix" on a serious motor.
Now, it's only a .005-7" difference between the rest.
In real life it shouldn't matter all that much.
You are not building a "tip of the spear" motor.
Yours is far more conservative than many.
I'd probably run it as is.
The .002" range difference between 1-2-4 I'd live with.
#3 at .041" I'd "fix" on a serious motor.
Now, it's only a .005-7" difference between the rest.
In real life it shouldn't matter all that much.
You are not building a "tip of the spear" motor.
Yours is far more conservative than many.
I'd probably run it as is.
10-4
That’s what I was hoping to hear…
In my perfectionist nature, is hard to leave things alone… Lol
I do have one wrist pin that’s a little heavy. I could take a few thousand off the top of the piston and then weight match it with the rest since I do have that heavier pin. If it’s worth the trouble to get them all within a tighter range. It’s true that it is just a street engine that will never see over 6k.
That’s what I was hoping to hear…
In my perfectionist nature, is hard to leave things alone… Lol
I do have one wrist pin that’s a little heavy. I could take a few thousand off the top of the piston and then weight match it with the rest since I do have that heavier pin. If it’s worth the trouble to get them all within a tighter range. It’s true that it is just a street engine that will never see over 6k.
I wouldn't worry about flawless balance on anything!
When running there is a bunch of oil that is "roping" around the parts.
It's stuck to the surface and moves around bigtime depending on rpm.
Makes balancing tighter 5 grams pretty useless.
Now when it is on the bench I'm trying to hit +/- 1 gram.
This is fairly easy to hit.
Balancing to a fraction of a gram is "practice bleeding" in my book!
When running there is a bunch of oil that is "roping" around the parts.
It's stuck to the surface and moves around bigtime depending on rpm.
Makes balancing tighter 5 grams pretty useless.
Now when it is on the bench I'm trying to hit +/- 1 gram.
This is fairly easy to hit.
Balancing to a fraction of a gram is "practice bleeding" in my book!
Ok…sounds good!
I’ll leave it alone and move onto rocker geometry with my new pushrods and swivel feet
I’ll leave it alone and move onto rocker geometry with my new pushrods and swivel feet
Important point!
Verify camshaft base circle is concentric.
See this thread.
http://www.914world.com/bbs2/index.php?showtopic=373021
You're all modern so I'd bet BIG money you're fine.
Not checking this while the engine is on the stand IS a mistake however!
Verify camshaft base circle is concentric.
See this thread.
http://www.914world.com/bbs2/index.php?showtopic=373021
You're all modern so I'd bet BIG money you're fine.
Not checking this while the engine is on the stand IS a mistake however!
It is a new Web cam that is advertised as base circle concentric. I should be ok, but will double check. That is interesting though that the stock cam was designed as such.
ALL camshafts should be "base circle concentric"
If I saw an advertisement like that I would ask "Are there other options?"
This is so commonplace that checking this stuff is usually NOT done!
I found it via a "fluke"
In a normal application with normal valve adjustment clearances, it wouldn't matter.
Because the T4 expands differently than a "normal" engine AND you fit steel pushrods most specs call for zero lash and that is where this type of deviation could create disaster.
This IS NOT something you can verify via paperwork!
HAS to be checked via a dial indicator IMO.
Paperwork that stated "base circle concentric" would be a red flag for me!
I'd hope what you found is a notation of "asymmetric lobes".
THAT is Ninja approved!
I'd pay MORE for that...
If I saw an advertisement like that I would ask "Are there other options?"
This is so commonplace that checking this stuff is usually NOT done!
I found it via a "fluke"
In a normal application with normal valve adjustment clearances, it wouldn't matter.
Because the T4 expands differently than a "normal" engine AND you fit steel pushrods most specs call for zero lash and that is where this type of deviation could create disaster.
This IS NOT something you can verify via paperwork!
HAS to be checked via a dial indicator IMO.
Paperwork that stated "base circle concentric" would be a red flag for me!
I'd hope what you found is a notation of "asymmetric lobes".
THAT is Ninja approved!
I'd pay MORE for that...
I’m off this weekend and will be back at it.
Can you explain the procedure using the dial indicator to check the cam?
I will do it on Saturday and make sure it is right. I am using the chromoly push rods so it needs to be perfect.
Can you explain the procedure using the dial indicator to check the cam?
I will do it on Saturday and make sure it is right. I am using the chromoly push rods so it needs to be perfect.
Drop dead simple...
Set up dial indicator so it replaces the pushrod into the lifter.
Rotate engine through 720 degrees.
You will notice needle movement through whatever degrees duration the camshaft says it has. Let's say 300 (big cam). the other 420 degrees is the base circle, and the needle movement should be VERY small if it is noticeable at all.
For use with zero lash the "runout" or variation should be .0002" (two ten thousands) or less.
Many dial indicators don't read that small.
What you are looking for is a solid needle during the "not on lobe" or base circle portion of the rotation.
My stock cam had somewhere between .0022" and .0024".
You would definitely see needle fluctuation with this much runout.
I'd check lift during this procedure as well. Tip of lobe to base circle multiplied by 1.3 should be very close to what the cam card says for lift.
Watch Karr's videos on setting up both pushrod length and rocker arm geometry and shimming. Good stuff!
Edit: You can find ultra-accurate dial indicators; they are expensive and "finicky" to use.
A normal cheapy version will work fine for this. Most are good to .0005.
You should see almost no movement on the base circle.
Set up dial indicator so it replaces the pushrod into the lifter.
Rotate engine through 720 degrees.
You will notice needle movement through whatever degrees duration the camshaft says it has. Let's say 300 (big cam). the other 420 degrees is the base circle, and the needle movement should be VERY small if it is noticeable at all.
For use with zero lash the "runout" or variation should be .0002" (two ten thousands) or less.
Many dial indicators don't read that small.
What you are looking for is a solid needle during the "not on lobe" or base circle portion of the rotation.
My stock cam had somewhere between .0022" and .0024".
You would definitely see needle fluctuation with this much runout.
I'd check lift during this procedure as well. Tip of lobe to base circle multiplied by 1.3 should be very close to what the cam card says for lift.
Watch Karr's videos on setting up both pushrod length and rocker arm geometry and shimming. Good stuff!
Edit: You can find ultra-accurate dial indicators; they are expensive and "finicky" to use.
A normal cheapy version will work fine for this. Most are good to .0005.
You should see almost no movement on the base circle.
Just had a post from Jack Standz in my base circle thread about aluminum performance push rods.
OMG this is the way to go!
https://vwparts.aircooled.net/ACN-Heavy-Dut...p/acnhdalpr.htm
I believe this shop is no longer in business but I'd search BIGTIME for those pushrods.
OMG this is the way to go!
https://vwparts.aircooled.net/ACN-Heavy-Dut...p/acnhdalpr.htm
I believe this shop is no longer in business but I'd search BIGTIME for those pushrods.
You can get those custom cut aluminum push rods from Germany. The same place that I bought my 10mm swivel feet adjusters from, offers them. I had already purchased the chromoly ones, so I didn’t get them. They say that they are much quieter and expand at same rate as factory, so they are better. Stateside tuning is the place to order if interested.
I did the base circle test on Saturday and it was successful, no movement on the cam lobe until the lobe starts it rise. The lift number on my 86a shows 436 lift on intake and exhaust side per the cam card, I’m only coming up with 418.6 ?
I had to stop there because when I pulled out my new Web lifters for the cam, I realized I was sent hydraulic lifters instead of solid ones. I’ll have to wait until I get the solid ones in before going any further with my build. I used one of my original lifters to do the test.
I did the base circle test on Saturday and it was successful, no movement on the cam lobe until the lobe starts it rise. The lift number on my 86a shows 436 lift on intake and exhaust side per the cam card, I’m only coming up with 418.6 ?
I had to stop there because when I pulled out my new Web lifters for the cam, I realized I was sent hydraulic lifters instead of solid ones. I’ll have to wait until I get the solid ones in before going any further with my build. I used one of my original lifters to do the test.
Type 4 rocker arms have different ratios for the intake and exhaust. Intake ratio is 1.36 and the exhaust ratio is 1.3.
A matched set of connecting rods can vary in length up to 0.010” due to the manufacturing process, but all the rods in the set will be the same length.
A matched set of connecting rods can vary in length up to 0.010” due to the manufacturing process, but all the rods in the set will be the same length.
QUOTE(technicalninja @ Jan 10 2025, 04:17 PM) 
Just had a post from Jack Standz in my base circle thread about aluminum performance push rods.
OMG this is the way to go!
https://vwparts.aircooled.net/ACN-Heavy-Dut...p/acnhdalpr.htm
I believe this shop is no longer in business but I'd search BIGTIME for those pushrods.
with John from ACN no longer selling I went to Tabari Andrade on Facebook
He may be able to help with something even better.
Rob
Great Find your always a great reference for Parts
Back when I was looking CB did not have these offered
Great Find your always a great reference for Parts
Back when I was looking CB did not have these offered
Stateside tuning has these available now. It only took about 5-7 days for my swivel foot adjusters to get to Fl. Super nice people as well….
Thanks Zigzag!!!
I feel better now that my numbers match the cam card….
I feel better now that my numbers match the cam card….
I ended up taking .002 off the top of the piston that had the deck height of .033 thousands. I then used the one heavy wrist pin that I had to place into that piston and all my weights are nearly identical. I then went back through all the other pistons and cylinders and switched them around until I came up with deck heights now of .035 on three of the cylinders and .040 on last one. Now I have a spread of .005 across my heights instead of the previous .007
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