318 hydraulic lifter preload.

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Large changes in piston and pin and/or connecting rod weights will no longer balance properly with the counterweights on the crankshaft. The counterweights are set to best balance the con rods and pistons and pins and such that are flying around and trying to throw the engine in all sorts of directions; i.e., excess imbalance will make the engine shake all over the place. Too large a piston weight change will do this.

The good news in your case is that your crank will only have to have weight removed to get back to reasonably well balanced (and not need weight added, which is more expensive). The KB pistons come very closely balanced to each other, so balancing them is not needed in most uses. If the con rods are close, then even matching their big end and small and and total weights can be skipped for much street use. (Ideally they would be properly balanced to each other but that is another cost.) With all of that, then you may get away with only the crank needing to be re-balanced; computing a new bobweight would be done and used at the shop to re-balance the crank.

Bobweights are the weights that are attached to the crankshaft throws (where the connecting rods normally attach) when the crank is balanced in a shop. For a V8 like this one, 4 sets of bobweights are attached, one each onto the 4 throws on the crank. These bobweights are used to simulate the weights of the connecting rod and pistons and pins and rings. This is purely a shop setup used to balance the crank to match the weight of the rods, pistons. The bobweight is computed to certain formulas (which you can do yourself for education with the right numbers in the right places). See here:
http://www.eaglerod.com/index.php?option=com_content&task=view&id=28&Itemid=25

In your case the piston+pin weight will change by 95 grams and the bobweight will go down by that amount; the change is well beyond a few%. That is getting where re-balance needs to be done, IMHO. Others may want to chime in on how much change they think is tolerable without excess engine vibrations.
 
One thing also for the KB's: They use floating piston pins, with the pins retained in the pistons with circular clips in the pin bores in the pistons. As some point, the 318's changed the connecting rods to use pressed-in pins; the later rods using pressed-in pins cannot use the floating pins of the KB's. I cannot remember when this changed..... so you need to check how your piston pins mount in the rods and pistons. If they have circular clips inside the pin bores in the pistons, then you are good to go.

Someone here is bound to know that off the top of their head.
 
The CC's can vary up and down a bit, BTW. Valve heads that are flat can take 2 cc's away from the chamber volume versus dimple headed valves, for example.
 
nm9stheham said:
One thing also for the KB's: They use floating piston pins, with the pins retained in the pistons with circular clips in the pin bores in the pistons. As some point, the 318's changed the connecting rods to use pressed-in pins; the later rods using pressed-in pins cannot use the floating pins of the KB's. I cannot remember when this changed..... so you need to check how your piston pins mount in the rods and pistons. If they have circular clips inside the pin bores in the pistons, then you are good to go.

Someone here is bound to know that off the top of their head.
Click to expand...

the 1974 and later pressed pin rod can be used with any pistons, the pin is pressed in the rod and the retaining clips are not used. the opposite can be what U are thinking-a press type piston with no retaining clip grooves needs more to be used with a floating rod
 
Thanks! I tend to get that backwards...sorry OP. So the OP's '72 rods will be floating pin rods?
 
yes all up to 1973 318 and 340s had rods with bronze bushings for floating pins. 360s were all pressed
 
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