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more cool head questions !!
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Posted by: lee37vernon

on a 76.5 mm bore 330 pro x top end with a pro design cool head , what domes would give approx what static compression ? whats the best place to buy them and do they come so your squish is all correct also ? this is an o ring version ..

looking at running our 'super' pump gas 97 - 99 pctane , what is max psi on that stuff ??

Posted by: punker69q

they offer three size of dome for your head, a 33c, a 30cc and a 28cc.

76.5mm bore x 72mm stroke = 330.94cc
with a squish clearance of ~0.045'' (1.15mm) your squish volume = 5.3cc

so your comp ratio, for each dome size:

33cc : (33+5.3+331)/(33+5.3) : 9,4:1
30cc : 10,4:1
28cc : 10,9:1

Your actual static compression (psi) is influenced by many factors, like your porting. On such a big bore (big bore are prone to detonation), I wouldn't run higher than 10:1 of comp ratio(with pump gas), so a 33cc is probably your best choice.

When you say 97-99 octane, that's research octane # right? Here our gas is rated with the R+M/2 method, and the motor octane (M part) is always lower than research #, so I guess that it is pretty much the same than our 93-94 octane gas.

Posted by: lee37vernon

RON / MON / PON . COMPARISONS

found this on net , pretty handy , you are correct , it appears my 99 ron is around 95 pon in USA . would you still say the 33cc
dome ?

thanks punker

Posted by: punker69q

You could always evaluate the integral in polar/cylindrical coordinates that represent the squish area equation, but if you don't know this already, I would need 200 pages to show you how.

Or, you can use this web page http://www.lmnoeng.com/Volume/CylConeSphere.htm and calculate the conical volume and subtract the volume of a cylinder of diameter Dtop. Using formula for corresponding geometrical shapes, you can get a very good idea of your head volume.

Posted by: lee37vernon

thanks punker69q .
i was looking at using this online calc ( as its free)
online calc

not looked at calculus for nearly 20 years so that helps . yet to see what figures i can conjure up .

Posted by: kiesta00

integration by parts is my fav

Posted by: lee37vernon

yeah , the disc method doesn't look too bad eh . suppose its quite straightforward really ,logically thinking . given my brain a dust off anyway .