My polaris pred 500 has a 12.5-1 piston, pure polaris pipe, k+n filter, and ported head/bigger valves and makes 42hp. So maybe you could use that as an example? I recommend 110 octane race fuel for optimum power and cooling.

 

I've got the optium power now with the hpd powermaxx setup and 110 race gas, just exploring some options in case the last cheap race gas station goes up to 7 bucks a gallon like the race. I'd rather be able able to ride with a little less hp than no riding at all![img]i/expressions/face-icon-small-happy.gif[/img]

 

Anytime you raise compression, you're gonna raise hp. There is quite a difference between the 4 stroke pred and the 2 stroke 400's when it comes to their hp and the mods you do to them. Though they will both benefit, the gains on the 4 strokes are more "stingy" when it comes to net gains. Though any gain can always bring a gain in the smile factor when you ride. [img]i/expressions/face-icon-small-smile.gif[/img]

 

the 15.5 dome is total smothness with a race mod engine,i got it
at over 185 psi on a fresh bore .020 top end,the 14.5 dome is better to burn fuel effiency but sacrifice lot of torque and compression altough,
110 octane gas,enough said!

 

I seriously doubt there is much if any noticeable difference between a 14.5-15.5 dome. enough said!!

 

I went from a 14.5 to a 15.5 dome and didnt notice any difference.

 

Well you see you have to know the dimensions of the domes times the width of the compression to the exact tolerances of the cylinder and to really get technical, you would also have to have the precise measurement of the spark continuity to develope a definite figure...enough said [img]i/expressions/face-icon-small-wink.gif[/img]

 

Couldn't have said it better myself![img]i/expressions/face-icon-small-smile.gif[/img]

 

freak,why darrell at HPD is tell me since i've been fine tuned that motor,the 15.5 is 185 psi and with 14.5 you got around 165 to 170 psi,that enough to make a difference for me at max output,as you raise
comp.,you need more spark fire then and the trick is done.

 

scramblered I know what hpd has to say, I was just wanting some input from other and maybe some that have run the pump gas race mod. I've got about every part hpd sells, I've had the race mod, race mod on alky, I now have the powermaxx engine with 210 psi of compression, I've got the hpd ignition, team secondary the list goes on and on and on. Your reply really didn't have anything to do with the question then you end it with enough said like what you had to say was the end all or something.