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Discussion Starter #1
I'm still in the planing stage for next years rebuild of my Big Block Chevy,its a 454 thats externally balanced.The pistons I've chosen are a bit heavier than the ones that are in it now,which arent the ones that came with the motor.The bottom end is still the way it left the factory as a LS-6 crate motor.I have a Fluidampr balancer on it right now and everything is smooth from idle to 6500 RPM.Will changing pistons upset the balance?Can I get this re-balanced externally?There is only one shop in the province that does any balancing,and it is probably expensive.
 

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Troll Hunter
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In a case like that I would lean toward the side of caution. It is only about $150 around here for a balance. In your situation extra weight will have to be added, probably to the flywheel. That's not too big a deal, it's when you start to add weight to the crank that the big $$ come into play. One of the reasons the factories went to external balance on many engine was limited space in the crankcase for bigger counterweights..... so just add it to the attaching components. You can save yourself a little change by checking and balancing the pistons prior to sending them. The difference in weight may not make a difference, but I would error to the side of caution when making noticeable changes.
 

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If the pistons are a little heavier that will make the crank under balanced which is not a good thing and the crank may require some weight added or mabe welding in the holes that are already there.

Having your assembley balanced will make a happier engine when its up and running.
 

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Discussion Starter #4
Thanks for the replies.After looking through my BBC books,I'm thinking that the pistons I am planing to put in might be the same ones as the originals.I'm going to put SpeedPro/TRW L2465 0.060 over,it had L2439 0.030 over in it when I bought it 5 years ago,but the original pistons may have been the L2465 model,I'm not 100 % certain,but hopefully someone here might know for sure.If this is the case there should be virtually no difference in weight,it was the second set of pistons that are currently in there now that were a different weight(lighter).It's not that I'm trying to be cheap,I'm just frugal!!(wife has me on a budget)
 
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