If you know how to mill a head, just figure out the actual compression ratio that you now have.Originally posted by Boss302man
[br]I realize port hight and exhaust duration play into compression and burn paterns. Scavanging also has effect on it. I was just hoping someone with stock ports and a similar setup could shed some light for me. I just milled the head at my house and wound up with 165psi. Im thinking about just test driving it and looking for early signs of piston wear. Im using the newer indy gasket which is basicly no thicker than a few sheets of paper so i can always throw a cometec gasket on to lower the pressure or even the old fat early indy gaskets to lower it more yet.
Look at the guidlines above and cut metal at your own risk.Originally posted by Jowen
[br]I have zr 700 -00 and I'm thinking of increasing the compression in it. I'm also planning to polish the ports. The original squish gap is specified to 0,069 to 0,091 and the effective compression ratio is 6,0:1. How much to you think I can decrease the squish if I use 94 octane?
Yes, but I think thats why myself and Studentdriver said rule of thumb check your squish band. A person can give equations until the cows come home. We gave answer that will help determine octane needs, and no its not gospel, but if you think that is wrong then the engine builders I know and talk to must be blowing sunshine up my a$$, that is one of the first thing they check (squish)Originally posted by AHood
[br]squish band clearance does not directly corelate to octane requirement. its far more complicated than that. you can not say if i have x squish what octane do i need. keep in mind as compression goes up squish velocity decreases.
compression ratio is calculated (full stroke volume + top of stroke trapped volume ) divided by top of stroke trapped volume.
and do NOT polish your ports its a waste of time just clean up slag and leave fine tooth texture. exhaust port can be smoother to resist carbon buildup.
Put a piece of solder trough the plug hole and against the cylinder wall. Turn the engine a few times and measure the tip of the solder. Modelling clay could work too.Originally posted by Boss302man
[br]so i check squish how?