Compression question WITH JE PISTONS 10.5

gearbanger4 · Post by **gearbanger4** » Wed Mar 14, 2012 2:25 pm

ok, I need some help with this one. JE pistons are claimed 10.5 that i purchased.....but is that calculated with the SOHC OR DOHC head?

Since I hear the combustion chamber is 52cc in the DOHC and 48? in the SOHC?. I am plugging in numbers to find my static (and dynamic compression) ratio into various online calculators....but want to make sure before deciding to mill the head, choose a specific cam etc. to achieve my desired compression ration. I am trying to accomplish this without having to physically measure everything. Calling JE awhile back did not help, but I figure they must have calculated that compression on one particular engine.....but which one?

Anyone ran into this before?

Public Disturbance · Post by **Public Disturbance** » Wed Mar 14, 2012 3:09 pm

MOST pistons I have seen are sold at there rated compression for the dohc and when you figure them for the single cam they are higher. For example my 8.8:1 pistons are actually 9.2:1 in a sohc for my turbo build

INVUJerry · Post by **INVUJerry** » Wed Mar 14, 2012 3:11 pm

When your ordered did you specify sohc or dohc? If not you probably have dohc pistons which are close to 11:1 on a sohc motor.

r/tguy02 · Post by **r/tguy02** » Wed Mar 14, 2012 4:11 pm

what jerry said

Aaron Clemmer · Post by **Aaron Clemmer** » Thu Mar 15, 2012 9:16 pm

so would stock dohc pistons be a good way to up my compression?

Public Disturbance · Post by **Public Disturbance** » Thu Mar 15, 2012 9:22 pm

yeah there are

ZeroChad · Post by **ZeroChad** » Thu Mar 15, 2012 9:30 pm

Hmm...I made a thread about this once. I have no idea where it went.

gearbanger4 · Post by **gearbanger4** » Thu Mar 29, 2012 9:12 am

Thanks for the input. When I ordered them, I didnt realize that compression would be different until after the fact. I called JE awhile back after ordering them and the guy who worked there said they only made one piston in 10.5 that works for SOHC or DOHC.

I kind of figured the 10.5 compression ratio was figured from a DOHC motor at JE, and putting them in the SOHC motor would bump me up in the low 11's for compression. But searching online for actual combustion chamber volume has yielded me with different answers. ranging from 46 cc to 48 cc.....and some saying over 50 cc?? Hmm. Maybe I am being to critical and should just install the pistons and be done with it. I just wanted to figure an accurate dynamic compression ratio (and thus an accurate static compression ratio is needed). Then maybe mill the head to get the compression a little closer to 11.5

Post by **occasional demons** » Thu Mar 29, 2012 9:52 am

esteinmaier wrote:OD, just cuz I know you love seemingly pointless knowledge, the stock DOHC head has a 52cc CC as opposed to the 48cc of the SOHC head.