First off I need to know where I can buy a quality compression tester. Secondly, do I do this when the engine is warm or cold? Reason I ask is I am putting on different headers and already have all the spark plugs out. What should the PSI be on a stock motor? Thanks!

Jeff

 

Ive always checked compression with a warm engine and the throttle wide open.

 

I would add pull the pcm fuse in the underhood fuse box, that should kill the ignition and injectors.

I tested just a couple cylinders on my 173K Roadmaster wagon just the other day and found just shy of 190psi I have no idea how this car was cared for or driven prior to my buying it at 172K a few weeks ago, once I get the carbon cleaned out I expect that number to go up a little. Most b-body LT1 reports I have seen are 190-205, that is with a lower compression ratio than you have which would cause a lower number than you should see but with a smaller cam which might make the number come back up a little so just use my numbers are a rough figure to get the ball rolling. Different compression gauges can read differently so the most important thing is not the numbers you see but rather consistency of the numbers you see.

 

Compression test

 

Shoebox, you are the MAN!!! Thanks!

 

I was taught to crank 6 times...but I guess 4 could work too