Inliners International Forums General Discussion Engines Engine/Clutch Noise

Newly rebuilt 292 engine. New clutch, starter, pilot bearing, throw-out bearing, and resurfaced flywheel as part of build. Ran engine for about 10 miles after initial break-in. No unusual noises during that period but then started hearing loud grinding/metallic noise at idle and while decelerating while going down the road. Noise diminishes and largely goes away when rpm come up (harmonic?).

Oil pressure fine (40 psi), water pump, engine top end, fuel pump all check fine. I thought Saginaw transmission was bad so removed, checked, reinstalled a rebuilt Saginaw- no change. While transmission was removed I rechecked the throw-out bearing- looked/felt perfect. Clutch looked ok although hard to really see everything. Noise/vibration sounds like it is emanating from the clutch inspection cover area.

Of note, while engine is running the noise lessens/changes when clutch pushed in but still have some noise.
When engine barred over by hand in neutral I can feel some roughness and noise but when I do the same with clutch pushed in the "roughness" and noise go away (all I feel is engine going through compression strokes).

Any ideas or other recommended checks? Thanks.

Did you adjust the shifer correctly? 3speed saginaw (on the tree?) or 4speed?

3 speed on the floor (converted). That is not a new mod and wasn't touched during rebuild.

Sounds like it could be one of a few different things.
First thing that comes to mind. Miss alignment of bellhousing to engine. If this is not indexed correct, the input shaft will be on a slight angle and be torquing on the input bearing. Making noise when clutch is not pushed.
Second- Makes me wonder if the flywheel is tight.
Third- Possible thrust bearing failure?
4th-Is the throw out bearing releasing from the pressure plate, not riding it?

about the of note thing: when you push clutch pedal everything behind clutch is not engaged so the roughness comes from the gearbox. If the noise is already present in neutral there is something wrong with the transmission, check the transmission when it's not istalled, if this makes no noise you have trouble with the clutch maybe it is not engaging properly.

Thanks for providing other things to check!
Transmission was swapped out with "new" one with absolutely same results.

If bell housing was misaligned it seems like it would have shown up earlier during run in? I don't know - just asking?

Any good way to check flywheel tightness and thrust bearing through inspection plate? Ideally without removing clutch. Assuming the flywheel was torqued properly do they tend to come loose so quick?

I was hoping someone would say inspection cover clearance or starter!

Here are a few things to check. Is the pilot bearing the correct one and if it is, is ti seated completely. I don't know how much mechanical experience you have, but I've heard of someone putting a pressure plate in backward. Check the end play on the crankshaft. Ccheck the operation and alignment of the starter.

To add to Wilcox, I have seen a guy put his engine together and forget to install a pilot bushing. He tore his tranny apart(it blew up).

I used the pilot bushing that came with the 12in clutch for a 292. Verified that throwout bearing is not riding on the fingers. When transmission was out I adjusted clutch linkage to allow bearing to retract ~ 1/8-1/4" away from the fingers. Hopefully that's enough. I'll check starter too.
Appreciate all the suggestions.

Today I removed the clutch inspection covers and found that I can rotate the flywheel by hand ~1/8" or so back and forth without the crank moving. Clutch is still installed so can't see much. So, loose flywheel bolts.

Assuming so, what is the best way to tighten them back up? No access to a lift so jack stands are it. Remove engine? Enough room to go through bell housing w/ torque wrench and then reinstall 12" clutch through the inspection cover? This is a '66 truck with engine supported by bell housing motor mounts.

When reinstall use loctite? I had used star lock washers in my last attempt.
Thanks.

I would look those bolts over real good. Maybe replace. Don't use star washers and do use green thread locker.
Are they 7/16 or 1/2? Probably 7/16 on a 1966.

Thanks Tom. They are 7/16ths.

Mr Gasket grade 8 flywheel bolts are available locally to allow me to get this done this weekend. I believe they come with star washers. If I do not use the washers is torque still ~ 110 ft-lbs?

On the older sixes there are 3 alignment studs in addition to the 6 shoulder bolts so even with loose bolts there is no end play. Is the 292 flywheel just aligned by the shoulders on the bolts? They would ALL have to have backed out beyond the shoulder to have play (which has probably trashed threads).

Also on the older sixes there are no lock washers - but instead there are three retention plates that straddle two bolts each. Once the bolts are torqued to spec the corners of the plate are bent up with a cold chisel and then these 'corner tabs' are pounded flat against the bolt head.

When did Chevy stop using these? Seems a bulletproof method of preventing the bolts from backing out.

If the shoulder depth of the bolt is designed for use with a star washer - eliminating it could cause the shoulder to run into the crank face (as the bolt runs out of thread). This would affect one's ability to torque the bolts properly.

Thanks, you've given some more things to consider. This crankshaft has only 1 alignment dowel pin. Believe that changed to 3 in '67 and newer. Double checking torque figures in Santucci's book show's 90 ft-lbs for 7/16" bolts vice 110 (1/2"). It doesn't really discuss washers.

Searching through the forum looks like star washers are not recommended by some very knowledgable folks but loctite is. Although frustrated that I have to do some rework I'm enjoying learning something new. Plus the bonus that I'm getting a little faster with tranny removals/installs.

The bolt torque is still dictated by the size of the bolt and not whether it uses washers or not. So stick to the recommended torque value for the bolt size you are using and you'll be fine.

When I was able to access the flywheel bolts they were all loose/finger tight. They had been fully torqued with reused star washers when initially assembled. This time I used new bolts, no washers, generous loctite and all seems well after a short test run. Thanks for your help and suggestions.