gpreston57
Well-Known Member
Going to do a compresion test on 74 225 with around 70k miles, what would be good numbers?
For a stock street engine with the Chrysler gear reduction starter and no major carbon buildup, that would be about right. For one with a Nippon starter, that would be a little low. For a carbureted race engine, that would be pitifull......its more important that they are all within 10%-15% of each other.i would expect around 125psi
I've always seen that caveat too but after testing several both with the throttle open and closed, I found at most a 5lb difference, nothing to fret over.do you have the throttle tied open.
Here are my compression numbers:
1- 100
2-90
3-100
4-105
5-85
6-70
looks like somethings up on no.6 maybe carbon buildup? Any suggestions?
Thanks Gary
As I said, it may bring them up 5lbs on the gauge at most. Think about it....the engine will run at idle with the throttle in the same position as when you're doing the compression test so there is enough air flow to produce compression under those circumstances plus if you have all the plugs out, you only need to draw air for the one cylinder you're testing. The others will move air in and out their spark plug hole.
Is it just me, or do I kill a lot of threads?