Small Block & Big Block Chevy Specific - 2 questions.....

I'm freshening up my 496 BBC over the winter. I want to just replace the rod / main bearings myself while its apart. All the journals looked really good and smooth, no grooves or anything. Most of the bearing looked good with normal wear, etc. but a couple rods and mains had a bit of junk embedded in them and have some slight grooves so I want to put a new set in. Is there a problem with doing that with out remachining everything? I wouldn't think so as long as I'm replacing them with the identical type bearing that was in it??

Also, anyone seen a timing chain that skipped a tooth when the motor was running? Mine apparently did sometime during the season. I found that out after checking piston-valve clearance and it was .010" on the intake. :eek2:

Thanks!

What do you mean by junk? Does it look like bearing material or just dirt?

I have never heard of a timing chain jumping a tooth? Was the chain still tight when you removed it? Maybe you were a tooth off on the install and didn't catch it.

By junk, I mean tiny bit of dirt and/or copper. Where its from I couldn't tell you. Here's a pic of the 2 worst ones.

The timing chain had a bit of slack but nothing I'd consider abnormal. I didn't install the chain originally so anythings possible, but I've put about 150 passes on the motor since I bought it so I can't imagine it not blowing up after that many runs with .010" piston to valve clearance.

By junk, I mean tiny bit of dirt and/or copper. Where its from I couldn't tell you. Here's a pic of the 2 worst ones.

The timing chain had a bit of slack but nothing I'd consider abnormal. I didn't install the chain originally so anythings possible, but I've put about 150 passes on the motor since I bought it so I can't imagine it not blowing up after that many runs with .010" piston to valve clearance.


What kind of RPM do you turn the motor to?

What kind of RPM do you turn the motor to?

7000-7200 normally

The bearings look ok....but are your oiling holes chamfered on the crank? It looks like there might be a slight amount of wear in that area.

I think you will be fine with just a bearing swap.

I can see no possible way for the chain to jump but strange things happen. Did the valves and pistons every touch? I would think with that RPM and clearance, something would have happened.

The bearings look ok....but are your oiling holes chamfered on the crank? It looks like there might be a slight amount of wear in that area.

I think you will be fine with just a bearing swap.

I can see no possible way for the chain to jump but strange things happen. Did the valves and pistons every touch? I would think with that RPM and clearance, something whold have happened.


Hmmm, dunno about the oil holes. Need to look at that for sure.

Yeah, it's doubtful I made 150 passes on it with it that way without going boom. So it had to have happened fairly recently. There weren't any marks in the pistons, but they were clean where the intake valves come close.

Thanks for the advice.

Lucky break on the valve clearance, thats strange. I would replace the cam bearings while the motor was apart, cheap and easy to do now.

Lucky break on the valve clearance, thats strange. I would replace the cam bearings while the motor was apart, cheap and easy to do now.

I would, but they all look really good. Plus, I don't have any way to install/remove them myself.