Compression Test question
 

Despite my efforts of doing my own research I have been unable to find what the acceptable/maximum/minimum cylinder compression is for a Ford 460 engine. The Chilton book I have for the 1986 F250 XLT only says that the compression should be within 80% of maximum but leaves ya hanging as to what that maximum compression number is. It also says that no two adjacent cylinders should have no more than 12-14 psi difference between them.

I recently did a compression test and have listed the results below. Additionally, is there any recommendations for a shop manual for 1986 Ford F250 XLT 4X4. I do like Chilton's but it does not always cover certain things in detail, hence this posting. I know that there is also Haynes manuals but IMHO find that Chilton's are more helpful even though it still sometimes falls short.

Cyl #1---120 psi Cyl #5---120 psi
Cyl #2---120 psi Cyl #6---110 psi
Cyl #3---110 psi Cyl #7---115 psi
Cyl #4---115 psi Cyl #8---110 psi

Thanks for any help/info,

Bill.

Low number withing 15% of top number. With today's low compression engines just about anything above 100 PSI is good as long as they are all fairly close to each other. I remember when 200 for a performance engine was iffy.

Did you have the throttle open when you took those readings? You gotta let air in to get a good reading. Also are those readings cold or hot? I just checked compression the other night on my '91 460 (cold) and high was 170 and low was 150 with most cylinders at 155 or 160.

Thanks, with the parameters established in your post then my numbers would be acceptable. Bill.

Yes, throttle was held wide open and engine cranked over 3 complete revolutions. Engine was cold. I was concerned of possible bad head gasket. Engine had miss when cold but miss seemed to "go away" after engine warmed up to normal operating temperature. No water in oil and no oil in water though. Miss at low temp was resolved for uncertain reasons. With all plugs out (they looked good with no abnormal deposits on 'trodes) nonetheless I replaced them all with new plugs, R/R the plug wires, distributor cap and rotor. After that, truck passed CA smog easily with 3 of 4 measurement readings being below average emissions.

Thanks for the response. Bill