What is this engine noise?

[Gary B.]

Re: What is this engine noise?

I had a simular sound on my `62 when I had the valve covers reversed. The lifters just barely touched the cover

[Dick W.]

Re: What is this engine noise?

Permatex Copper Coat silicone will take care of a head to manifold leak. A thin bead around the port will make it go away. Be careful to wipe any excess off. Poof! Your problems goes away

[Paul J.]

Re: What is this engine noise?

Patrick, it sounds like an exhaust leak. You've eliminated the heat riser, and you can eliminate the valvetrain by listening with a broom handle or stethoscope as Clem and Don suggest. You can also use a large screwdriver. However, I think that the problem is at that exhaust manifold.

Paul

[Patrick H.]

Re: What is this engine noise?

Permatex Copper Coat silicone will take care of a head to manifold leak. A thin bead around the port will make it go away. Be careful to wipe any excess off. Poof! Your problems goes away

We may try that first, though I suspect it has to dry first before we test it, correct?

I can occasionally see little "poofs" of smoke around the cyl 6 exhaust port-to-maifold area, but when I took off the fan and clutch to eliminate the air movement, I couldn't see them any more.
I did have this manifold checked and straightened before I installed it, though I suspect a leak is still possible.

I've tried exhaust gaskets on my 71 a few times and they always burned out within a year. When I finally had those manifolds touched up just to straighten them and installed them on the engine without gaskets they have not leaked a bit since that day.
I was hoping the same thing would occur here.

Patrick

[William C.]

Re: What is this engine noise?

Sure sounds tike a set of high quality exhaust manifold gaskets is in order for that side. (even though I generally don't use them either)

[James G.]

Re: What is this engine noise?

We may try that first, though I suspect it has to dry first before we test it, correct?

I can occasionally see little "poofs" of smoke around the cyl 6 exhaust port-to-maifold area, but when I took off the fan and clutch to eliminate the air movement, I couldn't see them any more.
I did have this manifold checked and straightened before I installed it, though I suspect a leak is still possible.

I've tried exhaust gaskets on my 71 a few times and they always burned out within a year. When I finally had those manifolds touched up just to straighten them and installed them on the engine without gaskets they have not leaked a bit since that day.
I was hoping the same thing would occur here.

Patrick

I think something is warped on the exhaust mounting flange, especially after you said it almost goes away as the engine warms. Years ago I found an intake manifold ''EXHAUST CROSSOVER'' passage crack. But this was an easy find.

I really think you have a defective ''HEAT RISER'' where all looks OK, but exhaust is blowing by the plate or one of the gaskets. That is what it sounds like to me, especially when you say near #6.

[Joe C.]

Re: What is this engine noise?

That's a BIG leak. I'd be looking for a crack somewhere. I wouldn't use manifold gaskets. Normally, if the flange is reasonably straight, any small leaks will carbon-up and seal within a short time. If you pull that manifold and examine it......................all over, including the heat riser valve...................then you'll see carbon/soot at the leak point.

[Terry B.]

Re: What is this engine noise?

How about a broken fuel pump spring that holds the fuel pump lever and rod steady on the cam? I know this would sound more like a lifter out of adjustment, but jusy maybe????

[Clem Z.]

Re: What is this engine noise?

How about a broken fuel pump spring that holds the fuel pump lever and rod steady on the cam? I know this would sound more like a lifter out of adjustment, but jusy maybe????

just remove the the fuel pump bolts and with the gas line attached pull the pump away from the block and start the engine. there will be enought fuel in the float bowls to keep the engine running to listen for noise.

[Clem Z.]

Re: What is this engine noise?

if you don't think you can hear the "hiss" with the plugged tail pipe have someone add GM top engine cleaner to the carb to make smoke and look for the leak. do this outside in the driveway not in the garage.

[Bill C.]

Re: What is this engine noise?

patrick,

I would not rule out the heat riser completely.
The movement of it matters, but also the fit of the rod/flap assembly in the cast part as well.

The original GM risers had a bushing inserted in the machined rod holes, the repros (most cheapos) do not, they are just drilled.

I would look to see if there is any sign of leakage by the counter weight/shaft and on the opposing side.
...
Bill

[Joe L.]

Re: What is this engine noise?

patrick,

I would not rule out the heat riser completely.
The movement of it matters, but also the fit of the rod/flap assembly in the cast part as well.

The original GM risers had a bushing inserted in the machined rod holes, the repros (most cheapos) do not, they are just drilled.

I would look to see if there is any sign of leakage by the counter weight/shaft and on the opposing side.
...
Bill

Bill------


Not all GM heat riser valves had the bushing. New valves with the bushing were introduced late in the 1966 model year. Prior to that time no bushing was used. The new valves also became SERVICE for older applications.

So, why were the bushings added? I believe it had to do with the introduction of AIR for the 1966 model year. This resulted in higher exhaust gas temperatures which probably necessitated "fortifying" the valve.

[Clem Z.]

Re: What is this engine noise?

the early ones also had a problem of freezing/rusting up and not moving so maybe that is why they added the bushings of a different material to prevent this

[Patrick H.]

Re: What is this engine noise?

UPDATE:

I went over to the car today and decided I'd take some of the advice given here.
I installed a high quality exhaust gasket (which I still think is an oxymoron ), tightened it up and the engine is as quiet as could be expected.

I still don't know why a manifold that was trued last year and installed with correctly torqued fasteners suddenly is not sealing well. That part puzzles me.
I will likely remove it in the fall, re-true it and reinstall it. However, that just wasn't possible in the short time I have right now.

Thanks for all of the suggestions!

Patrick

[Dick W.]

Re: What is this engine noise?

UPDATE:

I went over to the car today and decided I'd take some of the advice given here.
I installed a high quality exhaust gasket (which I still think is an oxymoron ), tightened it up and the engine is as quiet as could be expected.

I still don't know why a manifold that was trued last year and installed with correctly torqued fasteners suddenly is not sealing well. That part puzzles me.
I will likely remove it in the fall, re-true it and reinstall it. However, that just wasn't possible in the short time I have right now.

Thanks for all of the suggestions!

Patrick

Don't wasted the effort of re-truing Patrick, just use the high temp silicone and forget about it. It was the only way that I could keep the header gaskets from leaking on the dually I had with a built LS-6