Philitup 16 Report post Posted March 30, 2016 Hey guys I ran a compression test on my motor today. I bought the car with a swap, it's either a 68 289 or a 69 302 im not sure and neither was the previous owner. I have some smoke coming out of the tailpipe and when I removed the driver side breather had a little blow by coming from the valve cover. The plugs were covered in oil and the 8th cylinder was reading 65 psi and the 1st cylinder was reading 90psi. Do you think the cause is bad valve stem seals, bad piston rings, or both? Money is very tight right now so trying to figure out what to do. Also if there is any temporary fixes for atleast a short time to reduce the smoke and help boost compression please let me know as money to rebuild a new motor is not really feasible right now. Thanks a bunch Quote Share this post Link to post Share on other sites
Rsmach1 71 Report post Posted March 31, 2016 The loss of compression would either be rings, or valves. Stem seals won't cause compression loss. If the plugs are covered in oil and the compression is low you have a tired engine. I wouldn't bother with trying stem seals (although they are probably bad too). If the plugs are so oily that they don't fire properly you can try using plug foulers, along with a tired engine oil additive, but you are running on borrowed time, sorry. Quote Share this post Link to post Share on other sites
Dave R. 85 Report post Posted March 31, 2016 +1 on Rsmach 1's opinion. Dave R. Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted March 31, 2016 Yup, blowby out the breather is from wasted rings. Quote Share this post Link to post Share on other sites
Brian Conway 264 Report post Posted March 31, 2016 Yeah doesn't look good. Your compression readings are well below what even a tired engine would read. I don't remember for sure but I think 135 is a more normal comp. reading for a 289/302. Brian Quote Share this post Link to post Share on other sites
TexasEd 188 Report post Posted March 31, 2016 When I tested my 302 a few years ago I got 130-155 Quote Share this post Link to post Share on other sites
Desertdave 11 Report post Posted April 5, 2016 Hey guys I ran a compression test on my motor today. I bought the car with a swap, it's either a 68 289 or a 69 302 im not sure and neither was the previous owner. I have some smoke coming out of the tailpipe and when I removed the driver side breather had a little blow by coming from the valve cover. The plugs were covered in oil and the 8th cylinder was reading 65 psi and the 1st cylinder was reading 90psi. Do you think the cause is bad valve stem seals, bad piston rings, or both? Money is very tight right now so trying to figure out what to do. Also if there is any temporary fixes for atleast a short time to reduce the smoke and help boost compression please let me know as money to rebuild a new motor is not really feasible right now. Thanks a bunch How did you conduct your compression check? Did you do a wet and dry test? Quote Share this post Link to post Share on other sites
Max Power 74 Report post Posted April 5, 2016 How did you conduct your compression check? Did you do a wet and dry test? It would take a lotta wet to fix 65psi.....LOL! Seriously, valves not seating very well will cost you compression, but not contribute to oily plugs. Quote Share this post Link to post Share on other sites
