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Ok.. I did a compression check about a month after rebuilding the cyl. head on my car and got the following compression test results:
156
150
153
154

Not to bad, I was happy overall since I left the bottem end alone when I did the head.

Ok so now a month later I decided to do a compression check again to to make sure everything is going okay. Well here are the results:
150
145
148
150

Again not to bad, however I dropped about 5 psi across the board over the span of one month? At this rate I will need a rebuild in 6 months?! I don't get it a pulled all the plugs and they looked fine, nice brown color. When I tune for EGT I tune for safety at around 1550, so I don't think its too lean. I guess I just dont understand what's going on. The only thing I can think of is that when I did the first compression test it was probably around 60+ degrees out, whereas now it is about 30+. Would the colder temperature (denser air) affect the results at all?

As a final note, the car was at normal op. temperature, throttle open, mpi fuse out, EXCEPT I tested with all the plugs out, not just the cylinder I was testing. How much does this affect things? (It wouldn't affect the variance though because both times I did the test I did it this way).

Thanks in advanced for your responses =]
 

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Odd that is dropped 5 psi across the board like that. I don't think anything bad happened myself. Usually when something bad happens, one cylinder will take a crap, you won't see an exact 5 PSI drop across the board like that. It must have something to do with conditions.

Sounds like you did the compression test right from what I see. All plugs out, WOT, do what you can to stop fuel.
 

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Nothing to worry about.. compression tests are pretty inaccurate, you mostly want to see the consistency across the cylinders.

Hard to say what causes it, most likely it's a little colder than last time, you took a little longer, gauge is not accurate, or battery is not as strong as last time.

Don't worry about it
 
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