compression test

[dardal@xxxxxxxxxxxxxxx]

> When i get to the plugs, what would be a good reading at a 7,000+
> altitude?
> Kevin Pacheco
> 71 Imperial
> 
> 

I need to get my "standard atmosphere" tables out, but my guess is that at 
7,000 feet, you have lost at least 10% of the atmospheric pressure and thus 
density.  So, the compression test would be roughly 10% lower.  If 
the "recommended" number is about 150 psi, subtract 15.  However, the absolute 
number is not that important as much its consistency from cylinder to 
cylinder.  Low cranking speed due to weak battery or starter could for example 
cause low readings.  Also, if you do the test with all other 7 plugs missing, 
you will get higher cranking speed, and higher pressure.  So, it does not 
matter too much how its done, as long as you are consistent for all cylinders.  
If you detect one or two or more cylinders that are far worst that others, try 
pouring a bit of motor oil in the cylinder through the plug hole.  If the 
compression increases, that's bad news.  The problem is rings and the oil 
temporarily sealed the piston.  A complete rebuilt bay be eminent.  If not, the 
problem is in the valves which is easier to repair.  

The lack of power you were complaining about could be related to the high 
altitude.  The reduced density will cause a significant loss of torque, along 
with improvement in fuel economy, assuming the carb is not operating rich!

D^2