Possible main bearing problem ?

[nicanor]

The shop that is rebuilding my front end started the car for the first time (cold) and heard a noise that could be a bearing noise. It rattled a little as it warmed up. Just changed every component in the clutch system to make sure it was not the clutch. The person who built the engine was just around the corner so he came over. After the car warmed up for a few minutes the noise went away. This was done not in gear and the clutch not depressed. The guy who is rebuilding my front end was adamant that it was an engine bearing and said I could drive it until it really got bad. The engine builder said it was because the engine was built with forged pistons and that could make a little noise till they warmed up. The engine builder will guarantee the engine so after the front end is done, I'll continue to drive the car, break the engine in even more and listen for the noise. There is about 400 miles on the engine now. Any recommendations on how to troubleshoot or figure out if its a bearing or the forged pistons?

The restoration shop is going into the engine building business exclusively and I think he knows what he's talking about, but he might be looking for more engine work to get the shop up and running. He also said to cap off the vacuum from the distributor and disconnect the electrical choke off the Holley. Says its not necessary here in San Diego. Thoughts?
Thanks,
Barry

 

[peresvet24]

This may be the bearing in the tensioner pulley when the engine runs on a cold whistle he makes about 1-2 minutes.

 

[sixgunrunner68]

How's your oil pressure? Has it dropped at all? Bad main won't last long. You'd have to tear it down to check that stuff.
I'm not buying piston slap myself if it's that audible. I know you run forged pistons slightly looser but, just saying.
Do you have a hyd. cam? Sounds like a lifter problem to me. :cents:

 

[moparchris]

My motor in my Bee sounds like a diesel when its cold. I have yet to hear a forged piston motor with full exhaust that didn't knock when its cold. A spun bearing will be pretty quiet until it warms up, the rod expands and the oil thins out it will knock worse. So I would be willing to bet its piston slap which is totally normal and if it wasn't there I would worry. I would still cut the filter apart when you change the oil to look for bearing material. If it has a bad bearing it will have a lot of material in the filter.

 

[droptop]

Forged pistons will make noise when the engine is cold. If you have good oil pressure, drive it. I plug the vac advance on my cars. It runs better, but you will loose about 1-2 mpg. I got tired of people saying you lost a vac line, so I stuck a bb in the line and left in on.

 

[mcmopar]

My motor in my Bee sounds like a diesel when its cold. I have yet to hear a forged piston motor with full exhaust that didn't knock when its cold. A spun bearing will be pretty quiet until it warms up, the rod expands and the oil thins out it will knock worse. So I would be willing to bet its piston slap which is totally normal and if it wasn't there I would worry. I would still cut the filter apart when you change the oil to look for bearing material. If it has a bad bearing it will have a lot of material in the filter.

X2. Mine rattle around a good bit until it gets all warmed up.

 

[ALX69RR440]

My motor in my Bee sounds like a diesel when its cold. I have yet to hear a forged piston motor with full exhaust that didn't knock when its cold. A spun bearing will be pretty quiet until it warms up, the rod expands and the oil thins out it will knock worse. So I would be willing to bet its piston slap which is totally normal and if it wasn't there I would worry. I would still cut the filter apart when you change the oil to look for bearing material. If it has a bad bearing it will have a lot of material in the filter.

X2. Mine rattle around a good bit until it gets all warmed up.

X3

 

[ACME A12]

I got tired of people saying you lost a vac line, so I stuck a bb in the line and left in on.

Now that's classic! Gotta love it...

 

[george68hemirr]

X2. Mine rattle around a good bit until it gets all warmed up.

x4....but it rattles all the time with the whole car too :lmao:

 

[SomeCarGuy]

What oil filter you running? Junky Fram filters let oil drain back and that can cause some cold start noise.

That one guy sounds loony w/ his comments on the choke and vac advance. No reason to delete good running equipment. Sounds like "monkey see, monkey do."

 

[nicanor]

I hope to get the car back in about a week. Once that work is complete, I'll feel safer driving the car around town and I'll get a better feel for the car. I had pretty much just drove it around my town and on the open freeway to break the engine in. It does seem to get better gas mileage now that the engine is broken in fairly well.

Thanks for all the feedback.

Barry