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compression test.
For a compression test I take out all plugs. The idea is to rotate the engine as
fast as the starter will allow to attain a maxiimum reading, keep the throttle
fully open. This technique is cited in most of the literature.
For a leak down test it dosen't matter, but I would take the other plugs out
on some engines. An example would be to see if the head is warped. You are
just watching for air flow and looking to see where it escapes. As well as looking
for total air loss. Anything up to 10 percent is acceptable.
To evaluate an engine fully I first do a compression test. Look at the total on
each cylinder and if any cylinder is 20 lbs less than any other cylinder pour a little
oil into that cylinder. If the compression increases that indicates worn rings. If
compression does not improve it could mean worn,leaking valves. This gives you
more information of what to look for when you move on to the leak down test.
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