Do I need to rebalance?

[Wet Dream]

The rotating assy was balanced on this new 455 and the bearing clearances are on the tight side of tolerable for marine use (.0015) In talking to a few different people, rumor has it that I need to have the crank rebalanced. :( I talked to my machine guy tonight and asked him about it. He said that with a simple polish I won't need to worry about it since you are taking off equal material at the reciprocating ends of the crank, (rod journals) it essentially takes care of itself in regards to weight. The crank if anything really only needs a polishing to get me into the minimum of a .0020 on the rods, prefer to be closer to .0025, but .0020 will work. The mains won't (shouldn't) effect the equation. Does anyone have any insight on this or perhaps some words of comfort that I won't have to rebalance the assy?

[Hotcrusader76]

I would think you'd be ok with just a simple polish. Correct me if I'm wrong but the bob-weight would be the most important and I don't think you're going to effect that.
~Ty

[Fiat48]

Rebalance due to polishing the crank? Not hardly! Sometimes I wonder where this kinda stuff comes from.
On the bearing clearance. I guess you can get .0005 out of a polish. But you won't get .001. Even a crank grinder cannot grind just .001.
I'd like to see .0025. Any way you can get it. Possibly King bearings may make bearings for that. I'm not into the 455 stuff..but extra clearance bearings are made for Ford, Chevy, Chrylser by Federal Mogle.
Another thought is to call Callies Crankshafts. they used to sell and undersized bearing and some of the new coated bearings also have more clearance. .0015 scares the Hell out of me. Think about it. That's .00075 per side (or bearing shell half.) Not a lot of room for all important oil.
Here's king bearings search: http://www.king-bearings.com/cat/html/engines.htm
Further on balance...anytime we make a component lighter (as in turning a crankshaft)...we don't worry about rebalance. The amount is too trivial. And that's with motors than run 8500 plus rpm.
Are you checking bearing clearance with plastigauge or with mikes and bore gauge?

[gottaminute?]

Dont even think twice about it. polishing a crank for clearance will NOT effect your balance job. The estimated oil weights figured into the bobweight are greater than any change thru polishing. carbon buildup on the piston(s) after a good river trip will be more than what you will remove by polishing.
Not that it cant be read in a good balancing machine, just not enough to worry about considering all the other variables.
If you are still concerned about it, Call or PM me. been doin' it for over 30 yrs.
pat @ Balance Research 310 325-6478

[Wet Dream]

I still have to plastigauge the bearings. I'm just going off of what the engine builder told me he set the clearances at. If in fact it comes in at .0015, then I'll have to deal with options.

[Blown 472]

Originally posted by Wet Dream
I still have to plastigauge the bearings. I'm just going off of what the engine builder told me he set the clearances at. If in fact it comes in at .0015, then I'll have to deal with options.
Dont waste your time with that, mike the crank, put the bearings in the block and inside mike them, put the brgs in the rods and mike them, dont put the rods in the vise without some wood on both sides of it so you dont put a stress riser in the rod.