I've got a knock

[MoparYoungGun]

Sorry guys, this is a question regarding my Buick but it takes ALONG time to get any responce over on the Buick message board.

Anywho, last night I started her up and could hear a knocking noise. You could hear is clearer as you got closer to where there is leak in the exhaust pipe as well as where it exit's under the rear bumper. I am already thinking the worst. The weird thing is, we had the motor rebuilt around 12,000 miles ago (1998/1999). I am wondering what the problem could be and what I/my mechanics need to do to fix it. Thanks for all the help guys, it's much appreciated !

[sunfire69]

is it a knock, or a tick ? rods and lower end noise usally are load and solid sounding, valve train noise is quicker and more of a ticking sound (please these are just a rule of thumb and not hard and fast rules)
If you hear it close to the exhaust it could be as simple as an exhaust leak or burnt exhaust valve.
That might help you narrow it down some.
Jerry

[Ghoste]

This is a tough one to help with when we can't actually hear it.  Had you been pounding it hard or having trouble with overheating or oil pressure or any of those kinds of things before your knock arrived?

[MoparYoungGun]

No, I haven't been pounding on it, I haven't had problems with overheating (except one time last summer), and I haven't had problems with oil pressure. Also, I now noticed it only does it once it is warmed up.

[Ghoste]

That's kind of unusual too.  What Buick is it?

[MoparYoungGun]

It's a 1962 Buick Invicta Four Door Hard Top with a 401 Nailhead.

[Just 6T9 CHGR]

Possibly a loose plug?

[Chryco Psycho]

could be a piston pin not a brg

[Ghoste]

Why would it only knock when it's warm?

[MoparYoungGun]

Ok, I take back my comment of it needing to be warmed up. Basically, it needs to run for 10-15 minutes before making the noise. It doesn't matter if the engine is already warm and I shut it off, restart it, it still only happens after 10-15 minutes of it running. I'm really confused . I'm going to call my mechanics on Monday and see when I can either drive or tow it down there. I'm assuming I should have it towed? Thanks for all the help guys, it's much appreciated !

[Chryco Psycho]

if you drive it easy I doubt you would hurt it