67Olds442X2

I think I have it figured out but looking for a second opinion. I'm rebuilding a 455 and measured the main journals on the crankshaft which came out to:
2.9965, 2.9908, 2.9893, 2.9928 and 2.9907.
All are under the spec limit of 2.9993. I'm assuming I can't use std. bearings cause the bearing clearance would be too great.
Now I'm thinking the crankshaft will have to be turned so I can use the .010 oversize bearings. I'm I thinking correctly? I assume it would need to be turned to the point of achieving the magic bearing clearance. The mains in the block were center bored and are within limits. I have the same problem with the rod journals also. Thanks.

J-(Chicago)

In my opinion, you should shoot for .0025-.0029 on the rods, and between .0030-.0038 on the mains. Closer to the .0038 on # 2 and #4 mains. Those always seem to fry out first.
The rear main I usually go a little bigger, .0040-.0043

Now, a standard crank grinding shop will disagree with this because it is beyond factory spec in their books, but If you are going to be beating on it, you want the extra play.

67Olds442X2

Thanks for the info. I'll have to check 2 other crankshafts I have and see if I can get those numbers, or close to, without having to get one turned. If my forged one doesn't sell, I may use it.

cutlassefi

If your numbers are right that crank is all over the place. You'll need to grind that one .020 under.

I just had a 455 crank/block done for my current customer. The crank was ground to 2.9885, (essentially .010 under) which combined with sizing the main saddles to 3.1875, which is right in the middle of tolerance, gave me a little over .003 clearance on mains 1-4 and about .004 on the rear.

And if it's a street application I wouldn't use the forged crank, imo it's not necessary.

67Olds442X2

I checked my other two crankshafts and all journals fall within the spec range. I need to double check the saddle measurements again and do a comparison. The first crank will be saved for a later build, better that way since it's drilled for a pilot bearing and my other car is manual. Thanks again for the info.

Another question (dumb one) is what conditions require you to have the crank turned besides a spun bearing or a clearance issue. Do the journals have to be smooth as glass. Some of mine have faint lines running around them. Is there any limits? Thanks.

cutlassefi

If you can't really put a fingernail in them you're probably o.k. Other reasons to grind the crank would be taper along the journal or out of round to mention a couple.

67Olds442X2

Thanks. I'll have to bring it in to get turned, second thought, might as well bring the other one in and get it .020 under. It came with the motor I'm building.