Im having some issues with my truck and im running a compression check but im not sure what the ratio across the cylinders should be. I did cylinder 1 and it cam across as 118. Any one have the info for the compression please. i have the 360ci engine.

 

100 psi is a minimum, with no more than a 40 psi difference between the cylinders. Anything that falls within those parameters should be fine.

 

Compression test should be run on an engine that is fully warmed up. Wear gloves and pull all spark plugs on the entire bank. If a set of adjoining cylinders test low, screw a spark plug into one of the holes next to it and see if compression improves. That will point to a head gasket between cylinders. If one seems low, add a squirt of oil about one teaspoon to the cylinder and recheck. If it improves, piston rings are a likely culprit. A leak down test can further help diagnose the true cause of low compression.