Is my head gasket bad or rings?

Question

I have a 1980 chevy c10 pick up.
It smoked really bad for 10 minutes when I got it but ran great. all of a sudden I couldent go up to 65 m.p.h.. I checked the compression on all cylinders and all were good exept the one with 0 compression(dry test). The cylinder with no compression had oil on the spark plug. I cant hear any unusual noise, it smokes again, so is it the rings, head gasket or valves.

It has a hole in the muffler and my electric choke resently fell off and got lost

Answer 1

Bring bad cylinder to top dead center on compression stroke. Remove valve core from compression tester, connect it to and air compressor. Pressurize bad cylinder. Blow by air will tell you what went bad. eg. air rushing out exhaust/exhaust valve. air rushing out intake/intake valve. air rushing out oil fill cap/piston rings. air rushing out rad cap/head gasket. Very quick and easy way of diagnosing a low compression problem.

Answer 2

At this point it is as good of a guess as your own. With a Zero compression test in one cylinder and the no noise seams to me that would indicates a lower end problem. Not always mind you but on most of the engines i have worked on in the past. Could be a cracked oil ring or cracked piston. If it was a head gasket or a valve you would normally have a lot of blow back pressure and you have not indicated that. Best of luck with your rebuild.

Answer 3

a bad head gasket will allow oil to leak out. so yes the rings will eventually go bad but itll be due to the lack of oil. im not sure how you lost coolant from a head gasket. if possible get a compression tester from autozone or some other car store.

Answer 4

It sounds like it may be a cracked piston.

Answer 5

it seems like head gasket and psiton rings

Answer 6

probably valve spring