66 327 Engine Troubles

[Dan White]

I posted a few weeks ago about problems I have been experiencing with my 66 327: rough idle, backfiring on deceleration, and missing on acceleration. I did a compression check the other night and had some interesting results. All of the cylinders on the drivers side registered between 143 and 155 lbs, with the other two at 145 exactly (this seems alrigt to me, they are within 10%). The passenger side was a different story. Cylinder 2 had a reading of 140 lbs, 4 had a reading of 135, 6 had a reading of 145, and 8 had a reading of only 105. I put a little oil in 4 and 8, wich had no effect on 4, but brough cylinder 8's compression up to 140 lbs. I origionally figured I had valve trouble, but it looks like I might have ring sealing issues. Since the engine set so long, I figured it might be gummed up, so I am planning on running some detergent oil through it. Any further suggestions or tips would be greatly appreciated. Thanks again for all your help, Dan

[John Thomas]

Re: 66 327 Engine Troubles

Check for a bad head gasket, or God forbid, a cracked head.

[Craig S.]

Re: 66 327 Engine Troubles

John - I think John is on the right track with the ring sealing issues, since oil in the cylinder brought the compresson back up, a cracked head or head gasket issue is unlikely. I guess it would be worth a shot using a high detergency additive like CD2 etc to see if you can free the rings up. Is cylinder 8 showing oil burning on the plug?....Craig

[Craig S.]

Re: 66 327 Engine Troubles

Oppss....meant to say Dan not John...Craig

[Dan White]

Re: 66 327 Engine Troubles

Craig-
I am not sure what you mean by signs of oil burning on the plug, but the plug from 8 was very wet and smelled like oil. Thanks for the responses, Dan

[Craig S.]

Re: 66 327 Engine Troubles

Dan - the symptoms you describe are what I meant. The spark plugs should all show a light tan to white appearance when burning correctly, and appear dry. My guess is your other plugs are not showing signs of wet oily appearance. To me, it sounds like you definitely have a ring seal issue in cylinder number 8, the question remains if a high detergency cleaner additive such as CD2 can free this up or if you need a teardown to rectify the problem....Craig