compression test way too high : V-Twin Forum: Harley Davidson Forums

dej5320 · 09-26-2006, 09:46 AM

i decided to check my ccp after breaking in my 98 build (just to see where i was), and my reading came out WAY too high. i am running 37's with 84cc chambers (heads machined by HDWrench)...compression tested 268 rear, 270 front...i realize this can't be correct so my question is other than the gauge being bad is there something i'm doing wrong? i am using a second hand mac tools compression tester (CT100) i picked up a couple months ago. it was tested cold with throttle wide open, 3-5 turns stabilized at numbers shown above. did i miss something?...any suggestions?

Totenkopf · 09-26-2006, 10:51 AM

Quote:

Originally Posted by dej5320

i decided to check my ccp after breaking in my 98 build (just to see where i was), and my reading came out WAY too high. i am running 37's with 84cc chambers (heads machined by HDWrench)...compression tested 268 rear, 270 front...i realize this can't be correct so my question is other than the gauge being bad is there something i'm doing wrong? i am using a second hand mac tools compression tester (CT100) i picked up a couple months ago. it was tested cold with throttle wide open, 3-5 turns stabilized at numbers shown above. did i miss something?...any suggestions?

What are the gauge measurement units in?

dej5320 · 09-26-2006, 10:59 AM

measured in psi

Totenkopf · 09-26-2006, 11:13 AM

If all the above is true, then the gauge is bad. If those ccp numbers were real, your starter would not like it. Can you get your hands on another gauge to cross check with?

dej5320 · 09-26-2006, 12:42 PM

yeah, i'll try another gauge. i actually ran the test on a stock chevy 350 small block just to see what it read...it tested 210...way too high again. i just began to wonder if i was doing something wrong with the tester. thanks for the relplies.

**revperf** · 09-26-2006, 01:55 PM

The man speaks the truth. Gauge is bad.

dej5320 · 09-27-2006, 09:33 AM

new gauge gave me 195/198. still higher than i thought but believable. thanks for the help.

Totenkopf · 09-27-2006, 10:36 AM

that's going to be a perky motor! hehehe.....

The issue is going to be when the temp goes up, you will be more susceptible to pinging. The tune will be critical to keep it happy. 185 psi is a better compromise for a daily driver with nice manners but at 195 in nice air she's going to make some great numbers.