Tyler Ransom

Finally got my engine built and running. Did a compression test after 185 miles on it. Pulled spark plugs. Cylinder one the spark plug was loose.not wobbly loose but not tight. You could see the arking on the threads of the spark plug a bit. Cylinders two through 4 have 150 psi. Cylinder one has 120. My thought os the rings didnt seat properly. Is it possible to still seat these rings or do i need new ones on cylinder number one?

Tyler Ransom

Update: after driving and getting hot the compressions are as follows:

1----120
2----135
3----140
4----130 psi

hutch959

iTrader: (18)

evo 8... 9?

mods?

KingTal0n

also what kind of pistons.

I would be doing the compression test ice cold, make sure plugs are dry, look inside the cylinder if you can and smell for fuel leaks before anything,
You want nice even compression across the board. Use 2 different compression tester because usually 1 of them is bad.
Test the same cylinder several times. Get 3 or 4 compression 'hits' and WRITE the number down with a DECIMAL place. Try to be as accurate and exact as possible.
137.6
134.3
135.0
137.8

You want the numbers to be within 5% or 10% of each other ("you" decide what tolerance or difference is allowable when 'you' build the engine, the service manual has its own recommendation as well for factory builds)

The compression cold will usually be lower than hot. But the exact number is not important; what is important is that each cylinder seals up the same exact way. If one cylinder seals poorly while its cold, then they all should.