Help Me Crack This Puzzel
Thread Starter
Intermediate
Joined: May 2006
Posts: 49
Likes: 0
Help Me Crack This Puzzel
The engine idiling was running real rough not just a miss real rough, when I raised the rpm to 2500 it did smoth out but I could still feel a miss
I checked the following, Perfect Plugs, wires, fuel , No smoke no back-fire, No oil or anti-freez leaks
The next thing I did was a compression test all pistons read 150lbs and 1-read 30 lbs. I figure great I must have a burnt valve or blown piston. I rip the head off and this is what I found. The piston that had the 30-LBS the exhaust valve was bright white the a-joining exhaust valve was a light brown and the rest of the valves were a light black. The head gasket look good. I did the following to track the leak if any. I turned the head over and filled all the indent in the valves with tranny fluid in the hopes of tracking a leak "NO LEAK" (NOTE no sticky valves) Next I pourded at least six ounces of tranny fluid in the cylinder with the low compression and the same amount of fluid in the good cylinder and in the mornig I noticed that half the fluid was gone in the sick cylinder and in the good cylinder almost all the fluid was still there. The cylider walls were perfect the cylinders were also perfect.
No what. I hate to close thing-up with out fixing any-thing.
I checked the following, Perfect Plugs, wires, fuel , No smoke no back-fire, No oil or anti-freez leaks
The next thing I did was a compression test all pistons read 150lbs and 1-read 30 lbs. I figure great I must have a burnt valve or blown piston. I rip the head off and this is what I found. The piston that had the 30-LBS the exhaust valve was bright white the a-joining exhaust valve was a light brown and the rest of the valves were a light black. The head gasket look good. I did the following to track the leak if any. I turned the head over and filled all the indent in the valves with tranny fluid in the hopes of tracking a leak "NO LEAK" (NOTE no sticky valves) Next I pourded at least six ounces of tranny fluid in the cylinder with the low compression and the same amount of fluid in the good cylinder and in the mornig I noticed that half the fluid was gone in the sick cylinder and in the good cylinder almost all the fluid was still there. The cylider walls were perfect the cylinders were also perfect.
No what. I hate to close thing-up with out fixing any-thing.
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
The rings in your bad cylinder appear to be the problem. They allowed the trans fluid to drain past them alot faster than in a healthy cylinder- not the most scientific way I've seen to test ring sealing but it still tells the story. Between that & the lack of compression in that hole I'd guess that you have a broken or badly worn ring. There's no sense in putting it back together, so get after it & look at this as a chance to make your motor stronger. Good luck. 
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Lets see, your in Fl. and he is, who knows where, and you got it diagnosed? Those rings are going to have to be awful bad to only hold 30#. Its possible, and maybe your right, but a bad cam lobe will cause the same symptom. Unfortunely he didnt do the correct checks before he disassembled the thing, so now he is guessing.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
#30 thats really low-almost too low for worn rings.I could see #30 for broken rings but shouldnt that have shown some cylinder scoring and shouldnt all the trans.fluid disappeared?Why is that exhaust valve white?For that valve to be so lean that it was white it sounds like it was staying open for some reason.Check the lifter on that valve and make sure keeper didnt come out.Vette 73 did this condition happen all of a sudden or come over time.
