I'm will be running Kieth Black hypereutectic pistons with .002" clearance. I have the GM PM rods with ARP bolts. Will be using the stock crank and cast iron 350 block. The aluminum heads are Dart Pro 1 200cc. Also the car has the automatic transmission. Will not be spinning the motor past 6200rpm because of the Comp XFI-268 cam and stock crank.

Reason is my head porter could only mill the heads to 64.2cc because he was getting close to the 2.055 intake valve seat and the chamber polish also took away some. I was looking for around 61 cc for good dynamic and static compression but it did not turn out that way. Now looking for every little bit of compression including a .040" bore and the .031" quench.

By the way on DynoSim this combination looks very promising.

 

If it will see ANY street duty .031 is too close.
A Cometic gasket will get ya there but ya have to have a special finish on the heads and block for them to work(real smooth)
The 1074 Fel Pro is .039 compressed and would put ya .002 over the least I have tried(.035)
The quinch also depends on the kind of rod and RPM's ya gonna turn. Ya don't want to miss a shift and bang the heads with ALL 8 piston's.
Don't think I would go there with a stock bottom end.
If ya hit the head with those hyper-u-crap-tic pistons ya just bought an engine.

 

Not to hijack, but on my zero decked setup, is the 1074 a good choice with .039 quench? The engine will see alot of street and track time

 

Yes,built several like that with no problems.

 

Yes it will see mostly street duty and maybe 6+ times a year at the strip. I can program in for the computer to cut off the fuel at 6200rpm. Going to use the GM .028 gasket. So it just depends on how much I leave the pistons in the hole when I get the block decked. With the .031" I would have left them .003" on the hole. So if I go back to .035" that would leave the pistons .007" in the hole. Thanks for the replys.

 

Would it be best to stay with a flat-top piston at all cost or would a .100 flat dome work OK with say a .038 quench?

 

Do whatever will bring your DCR out to 9.0 or below.
This will be cam dependent.

 

I have the calculators. This is with a 4.020" bore and .035" quench. So with a .100 dome my static compression will be 11.18 and my dynamic will be 8.822.

This is with the cam installed at 1 degree advanced instead of the factory 4 degree advance ground in. That would be 66ABDC versus 63ABDC. Makes more power from 4000 up on Dynosim anyways. Only loose 5HP at worst down low but 15hp on top. We only have 91 octane available. Hope that will get it done.

 

If ya are planing to retard the cam with offset keys or bushings ya will have to get the computer redone as it changes timing an injector firing.

Get a bigger cam with the correct advance,go with flattops with 2 eyebrow, do what ever and figure it out before ya order the cam.

 

The best I can do with flat-tops is 5cc. This puts my static at 10.52 and the dynamic at 8.32 with a .040 bore and .035 quench. I'm running a Miezere electric water pump and it really keeps the engine cool. This is for a Gen 1 small block. I posted here because the engines are very similair and I would get a better response. I have the Cloyes 3145 timing chain. So depending on the quality control at Competition Cams I most like will have to use an offset key. The Cloyes has plus and minus 4 plus straight up. The degree wheel will tell the tale. Thanks for the replys.

 

WHAT heads are ya using? What CID? What cam?

This sounds all screwey. Ya building a 355 with a stock cam and just want to raise the compression? Or What?
Again I say ya will have to retune the computer if ya go dicking with the cam timing.

 

Ok. The aluminum heads are Dart Pro 1 with 200cc runners that have been milled, ported and polished. I can't mill the heads anymore than the 64.2cc without hitting the intake valve seat. They were advertised as 64cc heads but infact were more like 69cc and that is the problem. My head porter thought he could get the heads down to 60 to 61cc but it did not turn out that way. Intake valve is 2.05" and the exhaust is 1.60". Heads flow 264cfm at .500 lift and 276cfm at .600 lift.

The cam is the Comp Cams XFI268-HR13. 268 degrees advertised and 218 at .050". Intake valve closes at 63 degrees ABDC. Lift is .570 on the intake and .565 on the exhaust. Will be using all the good/stiff valve train parts including the 918 beehive springs. The block is currently a .350 Vortec 4-bolt waiting to be machined.

My current build is putting down 330rwhp and I'm building up a long block to replace it. Trying to squeeze all the horsepower I can like getting all the compression that is feasable on 91 octane and a .035 quench. Trying not to leave horsepower on the table for a street/ strip build. Tuning the computer is no problem as I have a custom tune now. Thank you for taking the time to answer my questions.

 

Whats the CID?

 

Right now 350 cubic inches. Will be going to to .030 or .040 so 355 or 357CI. Found some forged TRW pistons with a +3.40 two valve relief. That gets me up to 10.74 static and 8.49 dynamic. That is with the cam installed +1 advanced or 66ABDC. Hope the valve clearance is OK.

 

When I said computer retune,I mean the fuel and timing tables HAVE to be changed and ya can't do that at home unless ya got some pretty fancy equipment.
Ya need to check the P/V clearance with clay.