intermittent knock, Please help!

[monty509]

Ok did the test, don't know how accurate the numbers are since I didn't idle it to operating temp but it came out as follows,
1-85 2-55 3-49 4-76. Not very good i'd say.

Edit: I'm thinking I might take the timing cover off and have a look.

[TJones]

WOW, I’ve been scratching my head on this for a few hours now...
Could it be something in the bell housing????
Maybe a spring on the clutch that’s broke, a ball bearing on the throw out bearing???
It almost sounds like a bolt rubbing the flywheel as it turns.
But it may very well be internal????

[monty509]

I know, and what ever is causing it clears up and goes away whenever it wants.

[bmorgil]

monty509, before I say the numbers look bad, we need to know your process. How did you perform the test? You need to follow the service manual. On a cold engine and in general, we are looking for the following.

The service manual focuses on how well the motor compresses during the first four strokes. If compression jumps up "quickly" it indicates good pressure. If it is slow to come up and needs all four strokes to peak, it is getting "weak". If it is varying between cylinders, something is up. On these motors this is still a good way to check the general condition of the engine. It certainly has enough compression in 1 & 4 to start. Your test does not show what we want however. Cylinder 2 and 3 are to low to fire. On a cold engine cylinder 1 is what I am expecting. Does your test represent the service manual procedure? If it does I would say it is time to pull it down before it fails something, and costs much more to rebuild.

You MUST have an oil pressure gauge! I have to say monty509, don't start it again without one. If it is going away because the oil pressure is coming and going, you are causing damage that can render the engine very expensive to rebuild. These engines have very little oil pressure to begin with.

[TJones]

Your exactly right bmorgil, the oil pressure is Vital it will go into “cardiac arrest” if it’s not getting oil pressure from the get go and eventually it will be costly to repair over time.

[monty509]

Got a gauge in and it sitting at about 45-50. Trying to adjust the valves and am getting conflicting numbers Anyone know the valve adjustment specs?

edit: ive been using this as a reference. https://cj3b.info/Tech/Valves.html

[okiemark]

That's damn good oil pressure.

[monty509]

The more and more I think about it, I wanna say its probably a stuck valve. I got a mechanic stethoscope and did some listening. It definitely more of a click I'd say.

[gmwillys]

Try these videos to get a visual.

https://www.youtube.com/watch?v=9VrcG6tCQ2k

https://www.youtube.com/watch?v=zRClIFAg8W8

[bmorgil]

Excellent on the oil pressure. You are narrowing it down now. The cylinders with the low compression are probably the culprit. When the piston strikes the valve it can bend it. This usually causes a bad seal and aggravates the "sticking". You can pull the rocker shaft and exercise the intake valves. If one is sticking, it should show up when you manually open and close them. They usually stick as the valve is close to closing. The spring pressure is at its lowest.

If that's it, a valve job is a lot easier than a full tear down!