Low compression

[70c10stepside]

Hi all. My 355 I've realized a ticking noise come out the exhaust. Sounds like an exhaust leak but coming out the pipe itself. So readjusted the valves and it was still doing it. I've narrowed it down to the #7 cyl because it keeps killing plugs. But in away I've never seen. The plug gets pretty lol like really clean. With a slick texture to it. Well, when I done the compression test it read back 60. Squirt a little oil on the hole and it came back 90-100. Rest have 160 to 170. Motor is around a year old. Still has soft seats and that head. Other side lost seat but happened suddenly. And none of these other signs came with it. It just happened. It's 68 327 double hump heads, flat tops which may put it 10-5 to 11. So all the builders have told me. I had been running a vp mix with it for awhile to give lead and that little more octane. But didn't last fill up and here we are. Awesome right? Thoughts? I give enough info?

[70c10stepside]

Also. Even with this problem it still has loads of power. Blows the tires off still but it down a little.

[LONGHAIR]

Check the lift on the valves of that cylinder, could be a cam lobe going flat, although oil down the cylinder shouldn't affect that? Maybe broken rings?

Leak-down test?

[70c10stepside]

The valve appears to be opening and closing all the way. How do you do a leak down test? Now, on the way back home a second ago which is right at 20 miles, the entire way I felt it slowing down more and more. Each red light idling worse and worse. Last one I had to pop it in neutral to keep it alive. Ticking noise getting more clear. I believe its the valve..

[spatz]

Usually when you add oil and the compression comes up it means rings. check the noise with a broom handle or dowel rod to locate the noise before tearing it down to fix

[msgdsrf]

I wouldn't run any more than neccessary now. Leak down test and listen for any escaping air to tell if it's a valve or ring.

[zeldman]

If the plug is coming out clean, that is no carbon or no oily residue, I would suspect that cylinder is getting moisture/coolant in it. Possible head gasket problem.

[70c10stepside]

Zeldman, I was thinking the same. I have it parked, gonna drive my 67 for now till I can fix it. Thanks guys!

[storm9c1]

Originally Posted by zeldman

If the plug is coming out clean, that is no carbon or no oily residue, I would suspect that cylinder is getting moisture/coolant in it. Possible head gasket problem.

+1. That would also show up in a compression and leakdown test. Or that cylinder is not firing at all and gasoline is washing the cylinder. Does the "clean" plug smell strong like gasoline?

Either way, the news is not good. The bad compression needs to be investigated either way. It's probably time to pull the head.

[cableguy0]

I vote cam wiping out. its the only thing that will get that much worse that fast

[70c10stepside]

Its still firing, just 100 degrees off from the other cylinders from the header. And I wouldn't think cam just because the valve spring appears to still be opening and closing all the way. But who knows. Ima just pull it and go from there

[storm9c1]

Keep us posted. There are naysayers about today's oil and flat tappet cams. I'm trying to mentally keep track of those who have wiped cams to see if there is a real trend. If that's your problem, sorry about the misfortune.

[cadillac_al]

I think it's a burnt or bent exhaust valve. That's why you hear it down the exhaust pipe. If you're lucky that #7 exhaust valve may just be too tight.

[cableguy0]

Originally Posted by storm9c1

Keep us posted. There are naysayers about today's oil and flat tappet cams. I'm trying to mentally keep track of those who have wiped cams to see if there is a real trend. If that's your problem, sorry about the misfortune.

Being here as long as I have I bet there has been a few hundred threads of oops new cam just wiped out and almost everytime it was an engine that either didn't have proper break in performed or either the correct oil or an additive wasn't used. Also been quite a few that only used a zinc additive on break in and then changed to regular oil to have it wipe out a few miles down the road.

[70c10stepside]

The cams over a year old, at least 5k miles. We broke it in properly and no metal in the engine. So I'd say not. But I'll find out when I get around to tearing it down
.

[storm9c1]

No metal in the oil is a good sign!

[D.PASSMORE]

Originally Posted by zeldman

If the plug is coming out clean, that is no carbon or no oily residue, I would suspect that cylinder is getting moisture/coolant in it. Possible head gasket problem.

Had a pretty much same situation in my #8. Leaking (coolant) head gasket into cylinder. Once I figured it out, I put it off until the next weekend, motor was still running OK. Towards the end of the week, the cylinder filled somewhat up with rad juice. So, one morning go to start motor, it locks up, snaps my starter nose right off. So, new head gaskets and starter, yeah it was 3 day -dusk til dawn job! Ran for another year after that, valves/heads needed work, so I just bought a crate motor and put it in. Still running....

Good Linky:
http://www.4secondsflat.com/Spark_plug_reading.html

[70c10stepside]

It is the valve. Pulled it out and yep. Everything else is fine. Me and a buddy got it out and heads off in a little over 2 hours. Taking our time trying not to make a mess and stay organized. Not bad.. We are getting pretty routine lol