[chiphead]

My 400 has been making an odd noise from the front of the engine for awhile now. I replaced the water pump (leaking) and its still making the same noise. It's a cyclical, whirring crunch-grind-pop, crunch-grind-pop, crunch-grind-pop that's mostly noticeable at idle. It sounds like a combination of belt noise and alternator bearing noise, but the accessories are low miles.

It sounds like the alternator or the timing cover area. I changed the fuel pump and the water pump for other issues, but the noise hasn't changed. If it still makes the noise after I disconnect the belts, where should I look next?
Does a fuel pump eccentric ever fail? I re-used it when I changed the cam and timing chain about 2K miles ago.

[george kujanski]

Have you tried using the stethoscope method to localize the sound?

George

[steve25]

I have put the pump eccentric back on wrong once by mistake and only noticed it two days later when putting the cover.

Sorry but I can’t tell you what a bad one would sound like, I tell you what I would pull the balancer off just to see if the keyway is cracked or starting to crack.

[Formulas]

Lower pulley crack is where i would look next.. Pulling the belts would tell alot, then you could spin the alt. by hand to inspect that new doesn't always mean good... Same with the water pump

[7t4mula]

Could it be timing chain beginning to fail? How many miles on the motor?
Have you changed the oil since you stated hearing this? It might have some tell-tale signs in the oil. Hoping its nothing serious for you!

[pngoat]

Check the big balancer hub bolt for looseness. Should be 160 lb. ft. Next check the bolts that hold the balancer itself and the pulley to the hub. Should be 25 lb. ft. Also check the power steering (if equipped) pulley. Should be 70 lb. ft.

[steve25]

Also since the motor is a 67 it would have a full length windage tray and they have been known to crack and slap around.

[TXSTARFIRE]

On a 67 the balancer can seperate and make noise even if the bolts are tight. Easy to check. I had this happen when the rubber on the balancer completely went away. I noticed it when shutting off the engine the balancer outer ring continued to spin for a short while and made a whirring sound. The outer ring is captured so no danger of it coming off.

[Half-Inch Stud]

Check the Crank Pulley for 4 ovaled holes ( red rust from them holes).

Might be time to dril 4 new undersized holes, and use 4 fresh bolts ( or cooling fan studs).

[BB70]

Rub a bar of soap on your belts and see if it changes the noise. Sometimes antifreeze on belts and pulleys is really noisey, even when it gets washed off.

[Squidward]

I would run it with no belts, and see if the noise goes away. If it does, then add the alt belt and see if the noise comes back. If noise is still not present, add the ps belt.

You could also half split with the fuel pump too. You could fill the carb bowl manually, and run with the fuel pump disconnected and removed.

I remember years ago pulling a fairly fresh motor because an exhaust leak sounded like a rod knock. That is why my Firebird now has a 350. Noises are tough!

[steve25]

He has tried running it with no belts folks.

[chiphead]

Not yet steve. My next course of action is going to be to pull the belts Crank it up and let it run. About how long can I let it run before worrying about it getting hot?

[burd]

See if your 4 studs are too far through the water pump.

[70L34]

I'll pile on and say that a mysterious 'scratchy' accessory drive noise on my 67 GTO ended up being old belts. This is after I rebuilt the water pump, alternator, and PS pump.... I would have never guessed the belts could make such an odd and loud sound.

[steve25]

With a ambient temp of 60 degrees you could run a cold motor at idle for 3 minutes safely no sweat.

[Goatracer1]

Follow BB70's advice. You won't have to pull the belts and you can do 1 at a time. Besides soap I have used a crayon or candle.

[bluejudge]

Originally Posted by pngoat

Check the big balancer hub bolt for looseness. Should be 160 lb. ft. Next check the bolts that hold the balancer itself and the pulley to the hub. Should be 25 lb. ft. Also check the power steering (if equipped) pulley. Should be 70 lb. ft.

Yes, check on this suggestion. It cost you nothing to check. I had the same kind of noise in the front of my motor. Sounded like a bearing noise, or as I put it, marbles in a can making noise. I took the valve covers off and checked the rockers and it was not that. So I changed the water pump because it sounded like a bearing noise, it wasn’t that. Then I went to check the balancer, and it was the four bolts holding the pulley’s on. The bolts were almost sheared off. I was lucky to catch it before everything in the front of the motor let loose. Good luck…

[chiphead]

It's a '69 400 with the 11 bolt water pump and the later balancer.

Here's the results of today's testing:

Similar noise with both belts removed
Some belt and fan noise went away, making the rattling sound easier to hear. It sounds like sheetmetal contact/rattling/tapping near the center or front of engine.
All rocker arms adjusted and all pushrods spinning
Balancer is a nice SFI piece, not slipped or coming apart
Bottom pulley bolts are tight. RARE billet aluminum bottom pulley
I need to check balancer bolt with a socket, but the balancer didn't have any slack when I pushed/pulled on it.

On start, It doesn't make the noise for the first 15-30 seconds, then the noise starts. I stopped/started the engine 3 times, and there is a slight delay between engine start and the onset of the noise. Can hear it topside, loudest near the front. Can't hear it under the car, at least not over the exhaust. It almost sounds like the exhaust hitting something, that sort of rattley tink tink noise. But coming from inside the engine.

I pulled the fuel pump and used an inspection camera to get a few pics of the fuel pump eccentric. I used a screwdriver to move the outer ring to the front. It seems to have about .100 or so of forward/backward slack on the inner eccentric. The outer ring will sit flush against the gear or move forward as the pics show. Sorry for the weird angle, its hard to get in there and take pics.
Is this normal? I got a video too, but will have to upload it to YT later.

[mgarblik]

Well your eliminating some sources of the noise, so that is good. You could start and run it without a fuel pump and see if the noise changes. (sounds different, goes away or gets louder). That might help you zoom in on the fuel pump drive. if you don't have one, you could make a fuel pump cover out of cardboard for this test. Shouldn't make too much of a mess in 30 seconds. Any way to check if the thrust plate bolts have backed out and are contacting the camshaft sprocket? Not sure if you can see well enough in there. Also, is this a manual or auto trans car?