So my 1975 Duster with a slant six in it has a slight issue.

https://www.youtube.com/watch?v=KX2TgVH ... e=youtu.be

It sounds like a steam engine, and misses on one or two cylinders sometimes. Haven't opened the valve cover yet (or done anything more intrusive than a compression test) so I have no idea, but I think it could be some tight exhaust valves. Thoughts?

Sounds like it might be a sticky valve, but my computer speakers aren't so good.

What were the results of the compression test, reading for each cylinder?

Pull the plugs, line them up in order 1-6 and post a pic so we can see what they look like.

Brian

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I just replaced the plugs, and they were all pitch-black. No difference in them besides varying levels of oil on the threads. I can still post a picture if you want me to though.

On the other hand, I think I've found my problem cylinder. This compression check was done cold but I think it's pretty conclusive anyway:

Going from front to back,
Cylinder 1: 110 PSI

Cylinder 2: 110 PSI

Cylinder 3: 20 PSI

Cylinder 4: 85 PSI

Cylinder 5: 110 PSI

Cylinder 6: 90 PSI

Alright, so it's not exactly a sticky valve.



In fact, neither of the valves for #3 are moving. No idea why.

Edit: Okay, so I know why that one wasn't working, but neither of the pushrods are moving either.

Update - I believe I've found the issue. There is what appears to be a camshaft lobe lodged in the hole where the pushrod should go, and I can move it with the pushrod. As in, I can push it around inside the hole freely. I'm not even sure how the engine was running honestly.

Update to the update: Apparently, one of the lifters just popped out of its hole. Not sure how that even happened but I got it back in, right side up, with a $5 extendable magnetic flashlight from autozone. Just got done screwing the rocker cam back on and tomorrow I have to find valve adjustment plates so I can fix the gapping I obliterated earlier.

Verify that pushrod isn't bent.

Put it back together and disconnect the coil wire. Have someone crank it or use one of those remote start switches and watch all the rockers / valves.

Not sure if it's just the picture but it looks awfully dry and sludgy up there. If there's no oil getting up there that could explain this.

A lifter will easily pop out of its hole after the pushrod is no longer in place. At a minimum you should check your valve lash (on all valves).

I agree with Pierre; that top end doesn't look pretty. Once you've verified all your pushrods are straight, I'd start the engine with the valve cover still off. If you're not seeing oil at least dribbling out of the rockers, you'll want to pull the rocker shaft and clean it and the rockers thoroughly.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing