Non-Stoker High Comp. 4.0 pistons

[markeheiden]

Has anyone here built a high compression non-stroker 4.0 before?
Need 11 or 12:1 pistons for an otherwise stock bottom end 4.0 and no one seems to know how to get this done?
In case you are wondering, class rules prohibit strokers

[RAPTORFAN85]

Just plain your head. Will boost compresion without changing pistons.

[AaronJ]

11:1 or 12:1 ? Stock bottom end?

What are you doing? keeping it FI? Can you share more of your plans?

Aaron

[gradon]

Are you allowed to use oversize pistons? I used our handy calc and did:
+.060" 2229 silvolite pistons(available piston w/ smallest dish)
deck block the .042" to achieve zero deck(stock deck clearance is .0215" and the Silvos have a shorter pin height of .020")
use the .043 HG
Plane the head .020"
That'll get you 10.06:1 SCR
If you spend $500 on custom flattop(no dish) pistons installed w/ zero deck(would probably have a dif pin height, which would affect how much you deck the block to achieve zero deck), you can get the comp into the 11+:1 range (I calc'd 11.65:1 w/ the same .020" planed from the head--if you want more, remove more from the head). The question is what point above 10:1 would you no longer be able to use pump gas and have to use race fuel(or e85). The cam you choose could be the teeter-totter point.

edit: I had an idea:
People use the 2229s to mill bigger dishes due to their thick top. You could deck the rim/edges down to dish level to make a flattop piston, right(sounds easy enough for a machinist to do--measure the dish depth and deck the edges that amount)? Then you add that same amount removed to the .042" to be decked in order to achieve the zero deck. Feasible?

[markeheiden]

We are allowed to deck the block and go to max. .060" overbore.
The main thing is we can now run race fuel that is according to the vendor, good up to 13:1.
We are not interested in going that high but at least at 11:1 or 11.5:1 we should see some serious results over stock 9:1.
Also the stock bottom end is not an issue since we don't twist these things any where near 7 grand.
I don't beleive we can get there with just head milling and stock pistons. It seems silly with these motors being around for so long not one single manufacturer has decided to build H/C pistons for them.
This is apparently going to take a great deal more effort than I had hoped so keep the suggestions coming in!

[dwg86]

Custom forged.

[Flash]

I haven't done the math so it my not be even close but sense the 4.0L piston set .0215 down in the hole and KB has produced a stroker 9.1 and 10.1 pistons (this is meant for a stroker) but if it didn't cause the piston to poke it head to far out of the bore..............It might be an option


Flash

[markeheiden]

I believe a stroker piston would place the wrist pin further up in the piston. This would effectively move the piston down at TDC on a stock setup generating less compression instead of more?

[Flash]

I believe a stroker piston would place the wrist pin further up in the piston. This would effectively move the piston down at TDC on a stock setup generating less compression instead of more?

yeah, Your right

I'm going to half to go with dwg86 suggestion. Custom piston will get the compression ratio where you want it, and the best Quench available. You could even have a dome piston for that matter!!!!!!!

Flash

[gradon]

You would have to deck .27" to zero deck the kbs.

[1bolt]

I haven't looked into it yet but in my thread in Stroker basics someone mentioned the possibility of using a Chevy 6 cyl piston that is a flat top or has a pin hieght that would make it a pop up (or domed) of course it would need to have a pin height that works with either 258 or 4.0 rods and it would need to come in a bore size slightly under 4 inches.

To be honest I was hoping someone here had looked into it already but I'll do some leg work this weekend and see if I can come up with something.

My application is an E85 stroker with no block work (to achieve zero or negative piston to deck clearence, for super tight quench and high compression)

[Flash]

I haven't looked into it yet but in my thread in Stroker basics someone mentioned the possibility of using a Chevy 6 cyl piston that is a flat top or has a pin hieght that would make it a pop up (or domed) of course it would need to have a pin height that works with either 258 or 4.0 rods and it would need to come in a bore size slightly under 4 inches.

To be honest I was hoping someone here had looked into it already but I'll do some leg work this weekend and see if I can come up with something.

My application is an E85 stroker with no block work (to achieve zero or negative piston to deck clearence, for super tight quench and high compression)

With the kind of compression your striving for. A floating pin design would be a added bonus!!!!!!

Flash