I've read the FAQ on doing a compression test with a regular piston comp. gauge, my question is which plugs to take out. One link suggests trailing, other says leading plug. Also which is which? I don't want to assume but if I did I'd say trailing was on the bottom??? Just picked up the car last week, runs great, no smoke, I just want to get a baseline so I know the condition.

Many thanks

 

The key to remember is Trailing Top, Leading Lower.

It really doesn't matter which you pull from what I know. I usually do trailing as they're a bit easier to get at.

Dale

 

Well if both are the same than I guess I'm in good shape. I actually tested it a few nights ago on the leading plugs, not easy to do, so I tested under the car. I warmed up the engine, and got even compression on all three sides of each rotor, then I added the schraeder valve back and got a peak of 120 psi, same for both. I've used this gauge quite a few times and found it to be fairly accurate. I guess I'm in good shape.

 

You dont want a schrader valve so you can see the even bounce to 120 on all 3 sides of each rotor. Testing with a valve doesnt mean anything

 

I know, I checked it without the schraeder first, and got even bounces on both rotors. After that I put the check valve back in and tested for a peak. If the bounces are fairly even the valve gives a good idea of what the compression really is. I guess if the bounces are not even than that is another can of worms.

#9 towards the bottom.
http://www.rotaryresurrection.com/3r...ion_check.html