35fountain

Hopefully someone will know what this is...

I put a new set of heads on my 502's..One engine is making a clicking, tapping sound for 20 seconds after i shut it off and its coming from under the valve cover area. When it runs its smooth and has no valve train noise..It happens cold or hot..I adjusted the valves several times and set them differently to see if it made a change..Zero lash with a 1/4 turn, then i tried zero lash with a 1/2 turn, zero lash with a 3/4 turn.. I even cut up an old set of valve covers and adjusted them running .. With the valve cover and engine off i touched one of the rockers and you can feel the click..almost like something is moving still..It only lasts 10-20 seconds after shut down...
see video
Please help ??

Boat1

The only thing I can think off is lifter bleed-off of oil pressure on the valves that are on the ramp of the camshaft. You could try using a oil priming tool to create pressure, the listen when you stop priming. Possibly the inner spring is contacting something or check for clearance under the rocker arm to the retainer. Is the rocker arm contact point centered on the valve tip?

35fountain

Thanks..
Here's the video

http://www.youtube.com/watch?v=Lr6O4HYfEzA

35fountain

I was told i didn't have to put the rocker arms and push rods back in the same spot they came from..The rockers are stock stamped steel.. Is it possible there is a wear spot and they are not sitting flush and are at an angle of some sort causing that sound after shutdown ??

35fountain

Replaced the heads with exactly what was there..781 's GM Heads..The rockers have been there also nothing was changed..Your wrong about torqing the rockers..These are Gen 4 engines, not gen 5 or 6..The MPI's later models had torque down rockers and some of the HP500's. Mercruiser came out with a valve kit to change them over to adjustable rockers. The tapping/clicking happens when engine is cold or hot. It only lasts 10-20 seconds after shutdown. If it was expansion heat etc wouldn't it last longer.

Vinny P

Wow, thats an unusual noise. I cant say I have ever come across it before. While I dont know what it is, my opinion is that it is not a lifter bleeding down. I cant see that happening so quickly after shut down. Besides, a lifter will only bleed down when the engine is shut down while that lifter is on the lift of the cam. If this noise happens everytime you shut down, what are the chances of that being the case?
Being that a metal engine conducts sound so well, tracking down a noise like that will not be easy. I agree with you on the heat and expansion issue , it would take longer than that for things to start to cool.
I am sure you looked carefully, but maybe take a better look at the springs on that valve in question. Maybe the dampener is moving around? I am sure it would be a difficult job, but maybe you can air up that cylinder and use an overhead vlave spring compressor to remove that spring and take a close look?
Good luck with this one, I feel for you.

35fountain

Vinnie, Thanks for your response...This whole situation is very unusual to me.. I have been working on engines cars and boats for over 30 years and I have never heard a noise like this, especially when the engine is off ..LOL..Based on my video..does it sound like something is going to let loose.I haven't gone for a ride this season..A bit cool still.
and I would hate to just let it blow up without researching this more...

Young Performance

That is a very odd noise. I have seen some crazy things but ya got me on that one. Have you been able to pin down a side of the engine? I assume only one engine is doing it. Is it only one particular side of the engine? or both? Can you tell if it is in the front or rear of the engine? Does it seem like it's in the same place every time? Does it seem like the noise is the same intensity and duration each time? Does anything make it better or worse?
Just trying to get some info so maybe we can start eliminating some things. First, lets figure out what it isn't, so then we can hone in on what it is. Good luck.
Eddie

35fountain

Eddie, Great questions.. Here are some answers..
Right engine (port) did it until I re-adjusted the valves..No more noise.
Left engine adjusted valves still does it.. Noise is constant alternates left side right side..seems to be from cylinder 4 and opposite 3 to cylinder 5 opposite 6.. middle of engine..
same noise each time and same duration. I even held one rocker and felt a click...Hard to explain
Maybe its making this clicking noise all the time when running and i'm not hearing it until shut down,
maybe it doesn't get louder when reving up..like a rod knock etc.

Could this be anything to do with the new heads..The ss valves, springs, retainers were from the old set of heads.. They checked them and everything was ok..

I'm going to remove the rockers and pushrods today and see if anything is worn..

Young Performance

What lifters are you using? Which rockers? This will determine how much preload should be on the lifters when you set the valves.
Could there be any way the pushrods are rubbing on the head and that is the noise when the lifters bleed down? Did you check pushrod clearance in the head?
Eddie