scary eengien noise update

[Werner R.]

some might remember that i developed the gradual onset of a low pitched metallic knocking sound. it sounds loudest when i use the stethoscope over the # 2 and 4 headers. it also seems to be timed to the cam system rather than engine rpm, although i cannot be sure.
i used the gm upper cylinder carbon remover and it had no effect. i disconneted the spark wires individually and it had no effect. the knocking is NOT there at idle but only comes on, audibally, at about 2000 rpm and higher. i do not think the knocking is there at lower engine speeds. could this be timing chain expanding with speed and hitting cover?? can a bad lifter act like this?? rod bearing?? i think my next step is to check the valve lash just to make sure. if that is ok, then i pull the intake manifold and look. sound reasonable??
werner

[Barry Chappell]

Re: scary eengien noise update

I've had fuel pumps make a noise that appears to be valve related.

[Werner R.]

Re: scary eengien noise update

barry
i should have said that i run an electric pump. someone did suggest that the rod still in there might be doing this. any thoughts? i could take off the blanking plate and check things out. do you think i could remove the rod from the space where the mechanical pump used to sit?? might be worth it.
werner

[Michael H.]

Re: scary eengien noise update

Werner,

It's beginning to sound more and more like a hydraulic lifter that has a bleed down rate problem. At idle, the pressure on the lifter is much reduced and the oil feed exceeds the leak rate but at higher RPM, the bleed or leak rate goes up and the lifter is no longer at zero clearance.

A good way to check the bleed down rate is, with the valve cover removed, turn the engine over until one or more of the valves in question are open. As soon as the valve opens, there will be a noticeable bleed down of the lifter and the valve will slowly close. This happens because the valve spring pressure forcing the lifter plunger down will cause oil to leak out of a lifter that has internal clearance problems.

With the engine running at idle and the valve cover removed, you can push lightly on the push rod end of the rocker arm and if the bleed rate is too great, the lifter will begin to click almost immediately.

We are talking about a hydraulic lifter motor, right???

[Werner R.]

Re: scary eengien noise update

mike
i should have repeated what i mentioned in the earlier posts. i have the mechanical lifters.
werner

[Michael H.]

Re: scary eengien noise update

Ok, whole different deal in that case. Still sounds valve related tho...

[Barry Chappell]

Re: scary eengien noise update

I wouldn't think the rod would be active. It should just be resting against the plate.
Is there a chance you have some abnormal wear on the tip of a rocker that could cause a mating problem with the top of the valve.? Maybe not showing up using a feeler guage when checking adjustments.

[Duke W.]

Re: scary eengien noise update

What cam and what clearance are you running? When was the clearance last adjusted? Is the valvetrain generally "noisy" relative to what you think it should be or relative to other mechanical lifter engines you may have heard?

Duke

[Don Barnes]

Did you pull the valve covers off yet?

Werner pull the valve cover off and look at the rockers and push rods are you running the stock stamped steel rocker arms if so it is possible that the pushrod has broken through the rocker arm where the two come together check and see if the pushrods have preesure on them when they are just sittng there with the engine off look at things and see if it looks normal with the covers off if it is cam and valve train related that something should not look right to the eye and lead in the right place.but you need to get the valve covers off and look at the rockers , the rocker studs and the pushrods.just my two cents.Don

[Brad K.]

Re: scary eengien noise update

Werner,
You probably won't believe me on this suggestion but it's the honest-to-gosh truth. A couple years ago I rebuilt a low HP '65 vette engine with the steel valve covers. When we started up the engine, it had a wierd metallic tapping noise that I'd never heard before. It was coming from the passenger side. We tried literally everything we could think of over the next couple days. No luck..... What we finally discovered was a rocker arm was hitting the valve cover. These mid-year steel valve covers are designed such that they are slightly assymetrical (top-to-bottom, not end-to-end), but you really can't tell it, simply looking at them. On the passenger side it's easy to mount the cover upside down because there are no wire clips on it (plus...it didn't have a horsepower decal on it) We flipped the cover over and the noise instantly disappeared! Believe it or not! Not sure if this is your problem...but I would for sure take a look.
Brad

[Werner R.]

Re: scary eengien noise update

duke
the cam is unknown. as for lifter noise, it is somewhat clicky even after adjustment. i adjusted these about 2,000 miles ago. the engine was hot but not running. i believe i was on the base circle. i arbitrarily used .022 valve lash because, as i recall, that was the spec for the crane cam that i believe was used in this engine. of course i could be off. when i got the car it was very clicky and the lash was well into the .030's, so i suspect i have improved things.
the knocking noise is much lower in pitch than the high pitch clicking of excessive lash. i can visualize a thick metal rod [like the fuel pump rod] making this type of noise if it bangs against another piece of metal. the sound is sort of like that instrument that consists of two hardwood sticks that click together in caribbean music. i will check lash this weekend.
ON THE ISSUE of the california pollution proposal, i do have one additional thought. i know you are doing great on gathering facts and pointing them out to the appropriate representatives. however, have not the large classic clubs organized a saturday drive by of the governor's office in sacramento?? should not be too hard to get 200 or more classic cars there. obviously, everyone likes these cars, and i'm sure the press would cover this event. ought to get sympathetic attention from people. cannot hurt. this is the same idea as getting some nice sympathetic people in wheelchairs before the government when you want to pass legislation favorable to disabled people. very good luck to you.
werner

[Werner R.]

Re: scary eengien noise update

brad
i think that's a great idea, but as i sit in the office, i recall that the cover can only be mounted one way because of the holes for the cover bolts. i did not think they were symmetrical, but i will remove the covers this weekend and i'll see. certainly worth considering. thanks for the idea.
werner

[Werner R.]

Re: Did you pull the valve covers off yet?

don
excellent thoughts. the covers come off this weekend.
werner

[Dave K.]

Re: scary eengien noise update

I made this suggestion a week ago. Had the same problem with a 327/300 hp small block.

Dave Kitch
33108

[Joe L.]

Re: scary eengien noise update

Werner-----

If the cylinder heads are 1959 vintage or older, then the valve covers can only be mounted with one orientation as far as which end is "up". If the heads are 1960 or later, the valve covers can be mounted "either side up". With many of the steel valve cover configurations (but, not all), there is a different shape to each side of the cover, both the long "side" and short "side".