Hi there! This is my first post. My 54 ford y block has 62,000 miles and generally runs pretty good. I did a compression test on the engine today and need some help interpreting the results.

It's a completely stock engine, and the shop manual states the compression for a new engine is 130 psi. The readings on my engine are 100 to 107, but I may have made a mistake conducting the test.

I warmed up the engine, as the spec sheet in the manual implied. I also removed all the plugs. One thing I DIDN'T do though was open up the throttle all the way while taking the readings. I've read on the internet that this allows the cylinder to "gulp" more air. Would my readings be understated because of this? Or does it not really have that much impact on the results?

Also, the spec sheet says that the 130 psi is as taken at sea level...I'm about 1000 feet above sea level. Not important?

Those 2 things aside, how would you interperet 100-107psi on an engine that read 130 new? I have a little smoke (sometimes) when I start up, but it always goes away after 10 minutes of driving, and doesn't come back for the rest of the day. I've been told it's probably valve guides and not to worry. Would that effect my test results? Thanks - JR

 

I agree that the valve guides are the cause of the temporary smoking directly after startup, ussually if it's valve guides it occurs when engine is started after about 6 hours or cold, on the compression, throw that book away, 90 to 100 lbs is great!! and what it should be, and to run 100-107 average is what it is exactly supposed to be, Those start at 90 lbs and all other cylinders should be within 5lbs, like if one has 90lbs, then all others should ride at no more than let's say 94, and at 100, to have some at 107 and engine not shaking at idle specs, this is Perfect JR......Janet

EDIT: JR, i forgot to mention, but on factory book compression specifications, they mean with a teaspoon of 5weight oil placed into each cylinder before taking a reading, that boost the reading, as when you are driving a cylinder has a tiny amount of oil and gasoline on the compression stroke making it that result of 130, but a dry check JR would be about 100 or less as i said. The reading is aquired with a teaspoon of oil per cylinder with throttle closed, but if your engine isn't shaking and at that 100 to 107, drive and enjoy JR, sounds like you have a great old engine there.....Janet

 

Thanks Janet, for your lightning quick reply. You've put my mind at ease!! Now I can concentrate on fixing my speedometer and getting rid of my clutch chatter!! - JR

 

I'm glad JR, i'm a gal, but i go way way back and i love to help a fellow Yblock owner, on that clutch chatter, i had one in a 59 GMC floor shift pickup and it was the throw out bearing turning on the shaft when i would push in the clutch and sometimes at idle after releasing, oh man i worried about that big time, my step das father (a good old man) told me relax, it will probably whine to itself forever and keep working, anyway that's not that big of a job to change that...Janet