701 Superjet Stock head modification

[1550]

Friend of mine is raising his engines compression and ask me help to how much is stock superjet head cc:s, i cannot find any info about parts manual or service manual.

Or how much he should lower that head? He is gonna put enhancer and different prop in his machine.

 

[Mark44]

Need to check squish before you do anything that will tell you how much you need to take off the head.

Mark44

 

[stanton]

so they are they different from ski to ski? like you cant say take off .010" and bump up 20 psi?

 

[adet16v]

slightly different from ski to ski.....

everything has a tolerance when its manufactured so it will be slightly different from machine to machine when all the parts are put together.

 

[Rickster]

I'm not afraid to put my nads on the line.:biggrin:

three thousandths can be taken of a stock head on a stock 61x cylinder and that will raise the compression to approx 185psi.

:cool2:

 

[1550]

0,003 inch ?

 

[Mouthfulloflake]

ive got a stocker that was surfaced, skim cut, milled, cut whatever.

domes appear un-touched, I didnt measure squish, just installed, checked compression , it went from 140-170

lots of hours since them, no problems.
and its much snappier to boot.

 

[Rickster]

0,003 inch ?

Sorry, .030 of an inch. Thirty thousandths...

Stock squish is about .085 and taking off .030 will give you a squish of about .055 which will help your bottom end.

 

[stanton]

I'm not afraid to put my nads on the line.:biggrin:

thirty thousandths(.030") can be taken of a stock head on a stock 61x cylinder and that will raise the compression to approx 185psi.

:cool2:

thats quite a bit, so .010-.015 would seem safe without measuring squish...
...heey brett!! just say the word when your ready!!

 

[Rickster]

It's actually not that much, when you consider the cylinder base gasket is .020 (twenty thousandths) thick.