Piano Top Piston and Comp Ratio (Mahle)

[Guest Anonymous]

A.Morris stated that Mahle made 9.5 comp ratio pistons (thanks for the info). I measured my P Tops and they are slightly over 1/4 inches (~8mm) tall. Could these be the 9.5s or is that about stock hieght for a 'piano top'?

Thanks,

Robert

[Guest Anonymous]

I think those are the 9.5:1's. I'm building an engine with 9.5's and the piano is around .25 inch(haven't measured it though)

[Guest Anonymous]

down to get more comp? Or would the valves start to hit the pistons? I am having my head rebuilt and wondered if it can be taken down w/o endangering the pistons...

Robert

[Guest Anonymous]

Ever go to Bayarea02.com? Try talking to Ireland engineering. When you rebuild the head always gets decked a little. Very little, this will increase comp only negligable amounts. I don't think that you could cut the head down enough to make that much of a difference. If it gets cut what would happen if you wanted a nother rebuild? No more room to shave off!(that last little bit was just speculation) If I wanted higher comp in my engine I would have pistons made. They are not that much more than oem. Or you could switch heads and purchase oem pistons that run higher comp, that would require a different dizzy than you have(probally) or getting the one you have recurved. you would also have to run premium gasoline. Maybe depends wqhere you aare

[Guest Anonymous]

Hi.

A guy i know with an m10 e30 318i had his head shaved big time, like a couple of mm. CR he claims is over 12:1.

He has big issues with the timing. It affected something cos it is out somehow, and he reckons he needs a vernier cam gear. Something to do with it affecting the actual timing of the cam in respect to the crank. Seems like a big PITA. He does get 100bhp @ wheels, with only a very mild cam (not big enough to screw with injection crap)

That's all i know.

Best of luck

later dude

Michael S.

[Guest Anonymous]

DECK the block. MILL the head. SHAVE every morning in front of the bathroom mirror.