Thread: Crankshalf Barings and Rod barings

Tweet

How can you tell if a crank has been truned? My old main barrings have some numbers stamed on them-GMM400-A550B 4-325u7 My rod barrings have these numbers-GMM400-A54198-33187 The motor is a 327 out of a 1968 Chevy C-10 pick up. Is there anything on the crank itself. What are some things to look for. Thanks John.

Originally posted by Johnwalkeasy
How can you tell if a crank has been truned? My old main barrings have some numbers stamed on them-GMM400-A550B 4-325u7 My rod barrings have these numbers-GMM400-A54198-33187 The motor is a 327 out of a 1968 Chevy C-10 pick up. Is there anything on the crank itself. What are some things to look for. Thanks John.

Have the machinist check it with a mic.

if its been turned it should be stamped somewhere on the shaft with a #'s punch.

The machinist advice is the best. I have found where all journals were standard except one. Glad I caught it cause it could have meant doom for a combo I was refurbishing. Even if it's not cut, it probably wouldn't hurt to turn it to true it up. I don't like to go past .010 on mine unless they are fillet cutting it.

Judging by the GMM on the bearings, I would say those are the originals and the crank has not been turned. If you see .010, .020, or .030 anywhere on the back of the bearing shell, that is how much the crank has been turned.

Put the crank back in motor with startard barings. It truns fairly easy by hand. Has no play whatsoever. Feels good and solid. I think if it had been truned evan at .010 it would have been real tight. And the trun numbers were not on old barings. So I belive the crank had never been out of motor. The rear seal was like a piece of hard plastic. Also the rubber oil pan gaskets were hard also. Had to chip them away. All the gaskets broke off in pieces. But the motor was very glean on inside. Did,nt smoke. The main reason I took it out was because of the oil leaks. I think I,m partly the cause of that. Right after I got the truck, I took out the PVC. And I think that cause a lot of the leaks. Wont do that again.

I think if it had been truned evan at .010 it would have been real tight. And the trun numbers were not on old barings



Your may be ok with the engine, because it sounds like it has never been apart, but you are thinking backwards when it comes to your sentences above.

If the crank were turned at all, it would be LOOSE, not tight. When they turn a crank, they shave 10, 20, whatever thousanths off the journal, which makes is smaller. When you slip a turned crank into standard bearings, there is excess room, so it is loose.

Save yourself some headaches, take it to a machinist, and have him mic it to be sure. It is a bummer to go through all that work and then have the engine start knocking.

The machinist shouldn't charge much, or maybe even do it for free, hoping to get some future business from you.

JMO,

Don

PS: Take your old bearings with you, so the machinist can READ the wear pattern, and advise you if he saw any misalignment, or other stuff.

Yeah, Your right, I am thinking backwards. LOL. Thanks for corecting me.

Johnwalkeasy if you want to check the clearances get yourself a piece of plastigauge and check it yourself.


http://www.fordmuscle.com/fundamenta...ge/index.shtml

Originally posted by lt1s10
Johnwalkeasy if you want to check the clearances get yourself a piece of plastigauge and check it yourself.


http://www.fordmuscle.com/fundamenta...ge/index.shtml

Plastiguage is effected by temp. and humidity. It is for people who don't know how to read an inside bore gauge or mic.

Originally posted by DennyW
Everything is effected by that. What's up with you ? I use plasti-gauge all the time. Very accurate. Yes, I also know how, and have all the mic goodies.

It's for people who want something accurate, and save time on assembly.

Plast-gauge very accurate?? Oh,stop you are killing me!!Yes,I have re-con'd rods and watched the inside bore dia. change by me just handling the rods.

Originally posted by DennyW
So, your point is ??

Mine is, if your good, your good. Doesn't matter what you use.

You just made my point. Your Great!!

QUOTE
'Plastigauge can be obtained from all reputable machine shops. If your shop doesn't stock any, you ought to consider using another machine shop."
I agree with this Guy,

ERIK SAID "It is for people who don't know how to read an inside bore gauge."
whats plastigauge got to do with boring the block?

Originally posted by DennyW
YES, GOOD POINT FOR SURE MIKE.

denny,wonder how erik think most people checked bearings for the last 75 yrs? erik, just because you dont know what it is, dont mean it dont work for other people. its a way of life for a lot of shops. you need to get out in the real world more often.

The original question was "how can I tell if my crank was turned?" He didn't ask how to build a precision racing motor.

Within normal temperature ranges, plastigage will not vary enough to make a difference. It is more than accurate enough to make that judgement. If the crank is ground, it will be .010, .020, or 0.30. You don't need an inside mic to figure that out.

It is for people who don't know how to read an inside bore gauge or mic.

Eric,

If you read that again, you might see why someone would think you were putting them down with that statement. Just a thought.