Compression test

[boss]

When performing a compression test what is the expected results for a health 302?

 

[DirtDonk]

Unfortunately it's going to vary quite a bit by the particulars of the engine, but I would say that you're looking for consistent readings between 115 and 130 psi on a stock-ish engine, and maybe 140 to 180 on a modified one.

Things that make a difference are mainly cams and combustion chambers (heads and pistons) and intakes and exhausts.

Always do the test with all plugs removed, and the carburetor or throttle body wide open. All you're looking for at this point is a very small variance between all cylinders.

Paul

 

[DirtDonk]

I should probably have waited until I'd looked in one of the repair manuals. Might have given us a narrower window for a stock engine. I think Chilton's actually has something about it in their charts.
Maybe someone else will have their exact results from their own tests, or have better documentation than just my memory.

But I still think I'm fairly close.

Paul

 

[Steve83]

Click this & read the caption:

 

[Rustytruck]

When I bought my 1974 Bronco 38 years ago I did a compression test. On the screw in tester I use I got 105 psi across the board This motor only had 10,000 miles on it despite being almost 4 years old. 1974 was the worst year for the 302 especially mine being a California model with the cam set back 4 degrees, and deep dish pistons. My other 1974 Bronco came from Colorado with allot of miles on it and it has 115 psi. Most of the other years 302 smog motors were up around 125 psi Ford made several variations in the 302 depending on where it was shipped to and whether or not it was state smogged or federal or cars or truck models.

 

[boss]

Mine is a 75 shipped to Denver and from all indications is the original motor so from your experience I should be looking for at least 115 psi.

 

[AZ73]

Unfortunately it's going to vary quite a bit by the particulars of the engine, but I would say that you're looking for consistent readings between 115 and 130 psi on a stock-ish engine, and maybe 140 to 180 on a modified one.

Things that make a difference are mainly cams and combustion chambers (heads and pistons) and intakes and exhausts.

Always do the test with all plugs removed, and the carburetor or throttle body wide open. All you're looking for at this point is a very small variance between all cylinders.

Paul

Make sure the engine is at operating temperature first, then pull all the plugs and test. Note the reading on each of the compression strokes for each cylinder. They should all be similar across cylinders as they build up.