Other 760 compression, stock.

[davy87nj]

Looking for what a stock 760 engine compression should be. I have searched and seen a few people say its supposed to be lower in the rear cylinder. Then other people claim their 760 is 150/150 straight across. The one I have is 150/125. I was about to order some parts but remembered I heard something about these. Just trying to get the straight story. Manual is not helpful on the 760. Also if they are supposed to be staggered, why?

 

[98gti]

There's a thread in the fx1 section with some good info on the 760. The thread is 760 swap, it's like 5 down. I'd post it but I'm using my wife's stupid iPad and don't know how.

 

[98gti]

Sorry, it's titled 64x motor swap.

 

[GReenANt]

the volume in the head is larger in the rear cylinder lowering compression about 10 psi.

read this

http://www.groupk.com/tec-rearseize.htm

 

[davy87nj]

the volume in the head is larger in the rear cylinder lowering compression about 10 psi.

read this

http://www.groupk.com/tec-rearseize.htm

Great reading! Especially since I have two 1100 Yamahas with rear pistion scoreing issues, and I couldnt figure out why. thanks.

 

[davy87nj]

Sorry, it's titled 64x motor swap.

Also great info.

 

[GReenANt]

Yeah group K has tons of very detailed information explained what they did and why so you know they weren't just guessing.

 

[WatrLogd]

Given you two seem educated on 760's, do either of you know what undercut to make the domes?

 

[Matt_E]

I think you're referring to squish.
If you're talking about a stock 760 cylinder and a stock head, you need to end up at about 50 thousandths of an inch total squish at the very outside of the piston/dome. Figure in the head gasket thickness.

 

[fast superjet chase]

I run my 760's at 45 thousands and haven't had a single problem any smaller than that they will hit at high rpms

 

[WatrLogd]

Yes Im referring to the squish band. My machinist refers to it as the undercut of the dome. So 45 to 50 thousands. Appreciated.

I think you're referring to squish.
If you're talking about a stock 760 cylinder and a stock head, you need to end up at about 50 thousandths of an inch total squish at the very outside of the piston/dome. Figure in the head gasket thickness.