406 SBC Problem...HELP
 

I have a 406 that has not been run in about 4 years. I got it installed and started it up yesterday. When I started the engine it was making a clunking noise every second or so, after about 30 seconds that went away and she was purring like a kitten. I let it run for 5 minutes and then shut it down. About ten minutes later I started it up again, and there's a new clunking sound like something inside the block banging on the side. Started out happening once a second or so and eventually the frequency increased so that it was pretty much continous. I turned it off after a couple minutes and had to stop for the day.

Where do I go from here? What would you guys do to trouble shoot this?

I did have a small manifold to riser leak when I started it up but that was only for a few seconds until I tigtened the riser bolts a bit.

Mike

First thing to do is kill cylinders as it's running and see if it stops when you kill a certain one. I have seen a couple of these do this from a collapsed lifter, the pushrod will actually jump out of the lifter pocket and make a clunk noise at it drops back in. If it is a lifter it will not stop when you kill the cylinder.

OK...so I should run the engine and pull and replace plug wires one at a time and see if the noise stops on a certain cylinder. Is that correct?

I did set the valve lash yesterday before starting the engine if that info helps

If the noise stops you have a wrist pin or bearing gone. Hope for the noise keeps going with no fire.

Hey... long time no see folks!

Have you used the old "screwdriver to the palm" trick to take a listen in various places?

My thought is that something is probably sticking. How's the oil pressure look?

Tom

I don't know the screwdriver to palm trick, but it sounds to me like it's cylinder 6 or 8.

Oil pressure looked good at 65 -70 psi, and I did pull the distributor and spin the oil pump until i got some oil pressure before I started it up.

Sounds like a collapsed lifter.

are you handy at all?


Uncle Dave

I guess the best way to verify a collapsed lifter is to pull the valve covers. Does that sound correct?

Yes.

One time I had a rocker arm come off - made a hell of a racket.



UD

Yes, that is the way you do it. Also if you are going to pull the valve covers you can stop the noise if you find it by pushing down on the rocker arm pushrod end. If it gets quiet when you push on it that is the bad lifter.