one piston with 70psi compression
05-29-2009, 07:28 PM
#1
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one piston with 70psi compression
Changed the head gaskets, readjusted the valves, tune up, new carb, and a few other things. All I can think of now is the rings are probably causing this. The 70psi is only in one piston. The rest are around 120. Any other suggestions that I should do or is there a way to bring that compression up without changing the rings?
05-29-2009, 08:16 PM
#2
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IIRC, you can pour a little bit of oil into the low cylinder and take another compression reading. (DON'T HYDRO-LOCK IT!! use just a squirt or two)
if the compression improves, it's rings. if it doesn't change it's valves.
if the rings are bad, there's no easy solution. you can either live with it or re-ring it. leaving a little oil in there over night might help if it's a stuck ring
if the compression improves, it's rings. if it doesn't change it's valves.
if the rings are bad, there's no easy solution. you can either live with it or re-ring it. leaving a little oil in there over night might help if it's a stuck ring
05-29-2009, 08:51 PM
#3
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Wouldnt re-ringing it make it somewhat worse? If my engine hasnt been rebuilt ever or in a long time wouldnt the cylinders be somewhat oval and the rings be somewhat formed to that oval? So wouldnt new rings create less of a seal?
05-29-2009, 09:04 PM
#5
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yea I pulled the wire going to that cylinder and it didnt make any difference in how the car ran. Once I get the rpms up I can tell that cylinder starts to fire on occasion but its still not perfect. Ill try the oil trick.
05-29-2009, 10:17 PM
#7
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Yep that would happen. Are you getting smoke? Otherwise if it were leaking past the intake valve you would be getting backpressure in the intake and if the exhaust was leaking youd be smelling gas from the tailpipe.
05-29-2009, 10:59 PM
#8
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no smoke at all. I just put a new intake and rebuilt carb on along with new head gaskets so I havent really driven the car much. Its actually getting painted tomorrow. Is there any way I could check that its definitely the valves? How would I go about fixing that? Will it need a whole valve job?
05-30-2009, 03:56 AM
#10
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Ditto.....
When/if you do the leakdown test and have it pressured up with compressed air. You hear hissing in the carb....its the intake valve for that cylinder. If you hear hissing in the exhaust pipe its the exhaust valve. Pull the dipstick and put your finger over the hole and you feel pressure build up in the crankcase its the rings.
When/if you do the leakdown test and have it pressured up with compressed air. You hear hissing in the carb....its the intake valve for that cylinder. If you hear hissing in the exhaust pipe its the exhaust valve. Pull the dipstick and put your finger over the hole and you feel pressure build up in the crankcase its the rings.
