Knock When Idling.

[samoore0496]

I have a 66 110 Monza. When I bought it it had been in barn for 30 yrs. I changed the oil & filter, rebuilt carbs, etc. Engine started and ran well for first two short test drives. At the end of the third drive I noticed a loud knock when idling. It goes away when driving. Any suggestions? Steve M.

[flat6_musik]

Well, there's "clacking" and then there's "knocking". Hopefully, it's not your flywheel.

[kawtoy]

If you have a 4spd then push in the clutch. Does the sound go away? If so you have a loose flywheel ( very common). Might also be the fan bearing. To check you can take the fan belt off and run the car for a short time. If the sound goes away then replace the fan bearing. Could be many other things but these are the low hanging fruit and free to diagnose.

[64powerglide]

How about when you rev the engine? Does the sound go away then or just when you're going down the road. Sounds like a lifter knocking & when you get some RPM's up it fills with oil & quiets down. Try to pinpoint where the noise is coming from.

[samoore0496]

Sorry for the late reply. I have a powerglide trans. The noise only shows up after the engine has warmed up. It doesn't sound like a lifter. The knock is a heaver sound than a valve tap.

[vairsquared]

I had one do that. Turned out to be a broken piston skirt. I found it by pulling the plug wire on each cylinder while the engine was running, then see if the noise goes away. When it does, you've found the offending cylinder. Hopefully, it is something easier to fix...