[Johnny B]

Guys, I need some opinions on this one.

We've got a 350 with a 2442 crank that has a bad rod journal. It should clean up with a .010" cut. This motor had been balanced when rebuilt and ran great. (This is a 350 +.030 / 4 bolt with 487 heads and a 268HE cam. If it revs to 6000 it isnt often.)

The question is: When the rod journals on this crank are ground .010" will it need to be re-balanced? How about if it needs to be cut .020"?

The "Barnyard Mechanics" that I work with say, No, because the oversize bearings will make up the difference in weight. I say that cranks will allways need to be re-balanced for any changes that are made to the recip weight?

Whatta' ya think, Are we just splittin' hairs here?

Thanks.......Jb

[middleagecrisis]

Ask yourself how many cranks are rebalanced after they have the journals turned. I wouldn't think it would be necessary, especially in your low rpm engine. The imbalance becomes more critical as you move away from the center (like the pistons and rods) of balance. Just my .02 worth, I'm sure somebody with real experience will chime in.

[Steptoe]

A low rpm engine it will not make much diff...
BUT dtnamic balancing is not that expensive, so why not just do it anyway?
The old addage "measure twice cut once"

[Z15CAM]

I would not bother paying $340 for Balancing after grinding crank jourmals as it is a Consistent Bob Weight removal. You may be lightening the crank by 5 grams which benefits high RPM if the Pistons and Rods are slightly on the Plus Side.

Just how many times do you rev your engine over 5000rpm on the street. Every time you do it you're breaking the LAW and Subject to a FINE.

[Badbird]

I don't think balancing & blueprinting is as important on a street engine as it is on a race engine (6800 + rpm)......If this was a high rpm race engine then yes, I would have the crank, rods, pistons, damper and flywheel all rebalanced.

[BillK]

Johnny,
Grinding the crankshaft makes no difference at all in the balance. The amount of weight taken of the crankshaft is replaced by the increased weight of the thicker rod bearings and everything is about as close as you can get it to the way it started.

[Z15CAM]

Bill: Over the years we've been there.

[DOUG G]

I think you'll be fine as you're a low rpm driver.

[NICKO]

its cheap ins, rebalance it...never know when you need to make a by-run with a buddy in the car

[Steptoe]

I would not bother paying $340 for Balancing

Whooooo!!!!!!!
Thats about $NZ450 !!!
A full balance flywheel to pully is only about $175 here....

[Johnny B]

I appreciate the opinions guys! I like the realistic approach that you guys have.

I just talked to the guy that originally balanced the motor. He said after he cuts the rod journals he will spin the crank using the old weight numbers from the build sheet (if I can find it) since nothing else has changed. $75 plus $40 for the cut sounds reasonable enough?? If he has to start from square one to do the balance it is $300 and up. I am really curious how this turns out.

But, now I have to buy the guys coffee and wear a John Deere hat for a week! And, they graduate from “Barnyard Mechanics" to "Shade-Tree" Mechanics (I really don’t like J.Deere, but we won't get into that now!!)

Thanks.....Jb