91-95 HEADS & 96-97 PISTONS = 9x COMPRESSION?

[MyGt]

I'm trying to lower the compression on my engine '97 (stock compression~ 9.7: 1) So I can boost it a bit 8-9 PSI (BTW big intercooler too).

And I was thinking if using a combination of pistons and heads I could lower it...?

How about using 91-95 Heads with the pistions off a '96-'97

How much would this combination lead to, maybe 9.0:1 ??

I can always porte the combustion chambers of my heads to lower compression even more, and clean up any sharp edges that would lead to detonation.

Thanks!

[SappySE107]

Using those heads alone would be a better start. You can remove more than enough material to drop your compression. However, I don't know what would stop you from using 8-9 intercooled PSI on 9.7:1 considering the combustion chamber design.

[Anonymous]

I do not know if they make them for our motor, but you could try thicker head gaskets. That is what my buddy just did on his 383 stroker.

[MyGt]

SappySE107 do you have any idea on how much the new compression would be?

With just the (91-95) head swap, alone on a 96-97 engine?

My guess is that it will drop the compression. And if so by how much then?



I think I read somewhere that one could drop the compression on a '91-95 engine (with 91-95 pistons) from 9.5 to 9.2 with the porte of the combustion chambers of the heads alone! am I right on this?


The reason I wanted to drop the compression is to avoid detonation.

Thank you!

[SappySE107]

Well, stock 96/97 is 9.7:1. The CC for 96 is 54.5 and the CC for 91-95 is 51.5. Problem is the pistons didnt stay the same, the 96 have larger valve cuts (not sure on deeper, just more removed) and then a .030" dome put in the middle. You can hog out the combustion chambers and get in the 8s for compression.

[MyGt]

SappySE107, Do you have a best guess with the early design heads swap alone, on a '96/'97 engine?

Thanks!

[SappySE107]

not really, cause I dont know what the cc is for the piston/block side. I think chris measured the 91-95 at 4 cc but who knows. If you put the 91-95 heads on there, i dont see any reason you couldnt run whatever boost you are looking at. I dont know much about turbos and no clue what one you are going to run.

[MyGt]

How could I meassure the CC on the piston/block side?

Thanks!

[SappySE107]

you would need a burrette and have the piston at TDC. Then, you have to make sure the rings don't leak any of the fluid...which would be hard. Then, you have to account for the part of the piston that is actually above the deck and subtract that from the total.