Does anybody know what the ideal compression(psi) should be in a 96 Mustang GT, 4.6L SOHC? I did a compression test the other day and cylinders 1 and 2 were around 120 while the rest were about 140-150 so I figured they were the two odd out and probably had a compression problem, but I'm not sure so just looking for some solid info.

 

140-160. Unless your having some consumption or other issues, I wouldnt worry about it.

 

Did you prop the throttle open when you did the test? If not them low and inaccurate values will be recorded...

 

Ok well thats a bit of relief. But I don't really have a consumption issue but a bit of oil burning is all, and I was told that could just be the valve seals.

 

Having low compression can be the result of a few things. If it is 2 adjacent cylinders, it could be a partially blown head gasket.

If you have low numbers you need to do a wet test. Basically squirt some oil in the cylinder and re-test. If the numbers get higher you have an issue with rings as the oil acts as a temporary seal. If the number stays the same it could be valve guides or seals.

I would also perform a leak down test. This is a more accurate way of determining what the issue is. Not only to do you want to hold the throttle open as cliffyk stated, but it is best to perform these tests with a warm engine.