bbxlr8

Hi all,

I am stumped and feel pretty stupid about not being able to figure out what is going on & need advice. Noise seems to be coming from the front of engine low near harmonic balancer, but I know that can be deceiving.

It is a definite rhythmic rattling that showed up on a short errand two weeks ago on the return trip. At the time it started like a squeal like from a water pump or pulley. Did not have time to dig into it and last week I started it up and after hearing nothing I ran another short trip. Same thing on the way back and evolved into the rattling that had me thinking really bad thoughts about internals. But…engine & gauges are fine and it is running great.

What I did so far, jacked up and listened from all around. It definitely SOUNDS like the front but I know how sound travels and it is a side pipe car so that is debatable. Checked p. steering & slightly low fluid - topped up. Checked all bolts and pulled the both belts for the PS & alternator to isolate those rotating assemblies and noise still there. So far I did all of this with the car in neutral. THEN I pressed in the clutch and NO noise or rattle.

So I am thinking throw out bearing maybe? Anything else would be regular & rpm related

Background - I had the clutch replaced last summer with a Luk stock replacement and used the TO bearing in the kit instead of using the GM one. It was mid-summer last year and I had never done it before so I had a local, highly recommended mechanic do it. BTW - this killed me to hire it instead of figuring it out myself. I have pulled many auto trans & changed converters etc. but this is my first Muncie & vette & I wanted to get back on the road. Point is: mileage is low on clutch/TO bearing.

It killed me to be off the road over the long weekend, but I wanted to run by the group here. It is hard to go by descriptions and
I took a short video over the windshield with the clutch in/out and could figure out a way to post?

Any ideas or something I am missing or should try?
THANKS in advance!

Mossy66

Get a long screwdriver or a piece of metal pipe. Hold one end in your fist, but close to your ear, and lay the other end on various parts of the engine where you think the noise is coming from. It will be like a stethoscope, and you may be able to isolate the sound. Just don't stick the end into the fan.

In fact, check your fan to make sure it's tight. Mine was rattling on the power stearing pump shaft once. It's a close fit on a big block.


Gerry

anyChevy

I have a stethoscope, but 3 feet of garden hose does a pretty good job as well

bbxlr8

Thanks Gerry. Tried that and even have a stethoscope probe type thing but wasn't able to isolate anything meaningful. It is a 327 350hp so a bit more room.

6T7L71CPE

Once it's warmed up and rattling, put your hand on the clutch pedal. See if you can feel the rattle due to the TO riding on the clutch.

babbah

Could be your timing chain? Check it out.

Matt Gruber

i agree on timing chain. crank moves forward when u step on the clutch.

Fawndeuce

Check your fuel pump.



Paul

bbxlr8

Thanks to all for the suggestions so far.

Now the noise is definitely there at immediate start up (not just after warm up). So tonight I tested clutch pedal with my hand and it vibrates slightly (I can feel it but not doing much) AND the noise goes away when you move it in 3/4 of an inch before any real pressure is on it.

I had been thinking about the fuel pump, but the timing chain never even crossed my mind.

Another thing I thought of that I did when clutch was out was to replace the somewhat worn fork and ball stud with Paragon repro's. They sure looked like a dead on match to me and I am not suggesting any issue (just another piece of the puzzle?)

Any FURTHER thoughts based on the latest tonight?

Thanks again!!
Bob

Mossy66

One other thing to check is that tin dust shield between the engine and bell housing. if it touches the flywheel, and it's real close, it will make a hell of a racket!


Gerry

JohnGibson

steampunk c1

Check for crank movement back and foreword when clutch is depressed and released maybe timing chain or main bearing trusts. Timing chain can be checked by turning crank back and forward by hand .

bbxlr8

It's looking like bad news at this point. This week I had the guy that did the clutch & a recommended engine guy check it out with me and both think I am getting some movement in the crank (not good). Sounds like I caught it early & it is just starting to make noise against the timing cover. But also it looks like the fuel pump is starting to go as well (I did not notice the shaft wobbling a bit myself).

Immediate plan of action is to replace original FP with a stock AC Delco one and pull the timing cover to see what I can see. After that the only option is to pull the engine to really find out what is going on.

I knew the engine was an unknown when I bought it 8 years ago. It tested and ran great but had no history or doc's (which were taken into account). The car shows 39K on the odometer and from all of the other "tells" through out, and I believe it to be just 1X over at 139K. I made it as far as 2 owners back, the "story" was that it was rebuilt, but as we all know, that means many different things to different people. BTW the engine guy is a Chevy specialist and knew exactly what he was looking at (matching L-79) before I told him. Found out later through the trans guy that he also has a low mileage 66 BB top flight coupe as well as a number of chevelles & tri-5's.

SO, I am asking opinions again: This time, if it is as believed very probably the crank bearings (thrust or more) am I taking a big chance continuing to use it periodically & gently locally through this season and waiting to pull in the winter??

Fawndeuce

If it were my car, I'd change the pump first even before pulling the timing cover to see if you still have the noise.



Paul

bbxlr8

Thanks - Definitely the order I was thinking of.

jdk971

i believe if the crank is moving your oil pressure will go down. but i could be wrong. jim

Matt Gruber

timing chain noise is usually a worn out chain. No big deal.
yes change Fpump.
then check out chain, look for spot where it is rubbing, and measure crank movement to rule out thrust bearing.

DSR

[QUOTE Point is: mileage is low on clutch/TO bearing.QUOTE]

You can smoke a throw out bearing real quick if the clutch does not have enough free play at the top of the pedal. The bearing will be turning all the time if it's making contact with the clutch. It will make various noises as the clutch is pushed in & out.

Dave