Contour Enthusiasts Group Archives Forums Modifications Forced Induction Rounded options up Poll time.......

Originally posted by Buckshot77:

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Hmmm, where to start. I think you guys are completely missing the picture by not having built any of the forged internal motors.

I'm probably the one most influencing Burrita to do a bored out engine and no, I'm not the one building his motor, just an advisor. Here is the thinking as simple as I can make it:
1) 3L blocks often have multiple grades of piston sizes within 1 block. You cannot order forged pistons to multiple diamters to the .0001" in the same batch.
2) Forged piston manufacturers know the material they're manufacturing, have tolerances to .0001" and recommend bore tolerances based on their knowledge of the expansion rate of materials. Don't make the mistake you know more about using the manufacturers product than they do.
3) His current bore is trashed after looking at the condition of his pistons (I have them in hand). He must buy new pistons and if he wants to keep from having to buy a new block, he can just increase the bore size on his current block to the next level which I recommend in .010" increments. If he's currently at .020" overbore, then go to a .030" overbore piston and have the bore matched to it.
4) As far as stock internals go, he's all ready got forged parts, why does he want to go back to stock? Even if he wanted to go with stock pistons his only option is the OEM aftermarket type and depending on the weight, may still cause him to rebalance his assembly.
5) For balancing, the only way he should not have to rebalance the assembly is if the new parts are lighter than the last set or within a few grams of the old ones. If they are significantly heavier, than he must rebalance the crank as well.

Hopefully this clears things up.

Rick

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