what is the max compression you can run on pump gas on a stock bore/cam DS650??

 

11.5 to 1 runs nicely with premium pump gas, don't think you can go any higher

 

was thinking of doing a 12:1 and premium with octane booster. have a friend with a 12:1 he is getting rid of

 

Maybe throw 2 base gaskes at it.

 

Octane booster is "snake oil"...dont use it. When they say it raises the octane 3 points it actually means .3 points. So when you have 91 octane fuel and with octane booster its 91.3.

Depending on cam profile and ignition timing you can get away with very high compression. But for the most part 12:1 is about max on pump gas. Be sure to run colder plugs with high compression and pump gas.

And by the way the JE 11.5:1 piston is advertised wrong and the cometic stock bore gasket kit is the wrong thickness for a DS. So dont get this bad combo of parts mixed together or you could have a piston hitting the head.

 

I can't speak on the JE piston as its treated me pretty well so far but i first put in a cometic gasket and it was crap. I've always heard they were good but my roommates raptor has eaten three up as well. I've been running a stock gasket for 2 years now no problem.

 

What is the thickness of the stock head gasket?

 

What is the thickness of the stock head gasket?

 

.057

 

Compression is measured by 2 methods.
Static compression is what the physical dimensions measure.
The dynamic compression is what the motor actually produces. This is the meaurement when the intake valve closes to the head/piston volume.
This dynamic measurement can also be measured with a compression tester.
I have found that the DS can run on pump gas between 190 to 200psi if the humidity is under 45%. The DS can run up 200 to 210 if the humidity is above 45%.
This is based on running 92-93 octane. Some states call 91 premium and with that number I would run 10 psi lower.

OMR