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.

Thanks for all the advice guys. I hope to know more tomorrow. I think I'm going to go pull the valve covers and look for loose components. Hopefully that will be the problem, if it is I'll replace the cam and lifters. If I don't find anything loose in the valve train, I guess I'll run it on the hose and drop one cylinder at a time to identify the problem, and brace myself for the worst. I should be able to do the cam right where it is because everything is currently stripped out of the boat, anything else and the engine will have to come out. :traurig001:

Fixx
 

pull the filter and cut it open and look for metal shavings first..that should give you a idea where to go from their..

The valve train is tight. I pulled the valve covers this afternoon and there is no significant movement in any of the rocker arms. All of the push rods look good. I might have a chance to stop back by there later. If I pull the filter and find metal then what? What if I don't find metal?

Fixx
 

if you find big chips of metal pull it and do a tear down.. if not,,look else where,,are you sure its not the exhaust flappers? or somthing rubbing the bell housing?

This is a deep solid clunk noise I can't imagine exhaust flappers doing that. One thing that might be the culprit...a few years ago I added an oil cooler and perma cool t-stat. I'm not 100% that I have the lines plumbed correct, and I can't seem to find a schematc for either the Merc remote oil filter kit or the perma-cool stat. Does anyone have those? i need to know which port is the exit and which is the entry from the block adapter, and the same for the stat.

Metal flappers can cause a hell of a racket- certainly check.

pulling the cover and wiggling rockers doesnt really tell you anything-on a collapsed lifter the spring will still hold the arm in place- you need to start the engine and look at them.

safe to assume you pulled the plugs and looked for an obvious issue there?




Uncle Dave

Thanks for the info Uncle Dave. I wasn't sure if pulling the valve covers was a reasonable way to tenot. I didn't have the time to bring the engine home and run it today so no I haven't tried killing each cylinder yet. Hope I can do that tomorrow morning.

Update
 

1. No metal in the oil filter!

2. Oil was a little milky.

3. I've changed the oil, verifing the plumbing for my remote filter/cooler combo then i will run it and pull plug wires one at a time to look for an issue.