I called Andrews today a spoke with a gentleman named Gary. I'm installing a set of 57h in my 103". I call regarding the ideal compression for that cam becouse they don't list any compression specs for this cam. I am on the fence as to if I should install a cometic .030" head gasket along with the cam install to boost the compression and get alittle more bang. Gary to my suprise actually recommended that I do not bump the compression up for this cam. He claims I will exceed 185psi cylinder pressure and I will only make the motor sensetive to pinging on a hot day or with a tank of bad gas. Do you guys tend to agree with this or is this advise on the "playing it safe" side? This didn't seem like great news concidering that is was also concidering doing a 107 kit which I planned to use cp 10.25 or 10.5 comp Pistons with.

 

I think Gary is coming down on the conservative side. I am 600 feet above sea level in south Texas; summers are hot here. Using my calculator, I would run the .030" head gasket; 10:1 static CR. That would put corrected CR at about 9.3 and CCP about 190psi which is about where you would be assuming 85-86cc chambers and a bit of negative deck height which is typical of the TC motor. If you get a bad tank of gas, the motor would likely ping just as bad at 9.8 static as it would at 10. The tune will also make a difference in the tendency toward detonation. I would not run the 57 at 10.5 static but that's your call as well.

There are plenty of 57 cam installs on this forum; maybe some of those guys will chime in on their setup. I have no first hand experience with the 57 cams but from what I read, I think you would be happy with the cam in either configuration.

 

Hillside set my heads up for a 10.1 and I installed a .030 head gasket. I'm right at the CCP he mentioned and she runs great.

When I spoke to Gary he recommended not exceeding 10.1 ..... Wrong cam if you want higher compression. Great cam with mild compression. She does more than I expected her to.

 

I ran my 57h both ways, stock hg and .030 hg). You will be happier with the .030, a bit more seat of the pants low end.

 

I'm running 83cc chambers with the 57,s gives me 10.35/ 9.6 205 cranking good tune no ping running temp has never gone over 230*

 

All good info thanks guys.

 

I'm really loving the way my bike rides since I installed my 57H's. I'm running the stock CR which on a "wet head" is around 10.5 from what I've been told. I want to put a set of SE heads on but not until I get around 10,000 miles. At that time I will decide what gaskets I will use. I like my numbers but TN. Heritage has even better numbers than I got. I'm still playing with the idea of spending another $100.00+ to have another dyno shop do some tuning...just not sure if the money is worth a couple of extra H/P's!

 

Stock CR is 9.7.

 

A local builder told me real world was closer to 9.4 than the stated 9.7. Don't know the hard truth to that statement. When I put mine in Gary advised I did not exceed 10:1 From my research 10.25 is the highest w/o sacrificing performance of the 57 can.

 

Could be; every motor is different. I have seen TC chambers that are supposed to measure 85cc-86cc measure 89cc-90cc. I have seen deck heights run from -.003" to -.010". So of course there will be variances from one motor to another; some may actually show 9.7 or even a bit more but none will ever show 10.5 as Melman has been told; that would be too much for the 57.