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Author Topic:   Pistons and Balancing
Dirt Forum Racer

Total posts: 93
posted June 24, 2001 12:51 PM
My motor is balanced for a 145 gram piston, what will happen if I change to a 132 gram piston without rebalancing the engine? This a very heavy assembly using an aftermarket 5.7 rod in a 350 using a factory cast crank.
Thanks in advance.

Dirt Full Roller

Total posts: 74
posted June 24, 2001 02:35 PM
With that large of a change , you'll need to rebalance ! If it were only a gram or two in weight difference , then it would be close enough to get away with . But I think you are off a long way on what you think your pistons weigh !! 145grams and 132 grams ????

Dirt Forum Racer

Total posts: 93
posted June 25, 2001 11:48 AM
I think that's the advertised bob weight or something, it was in a tech department response I recieved, the pistons I have now are like 532 grams, and the High compression flattops come in at like 514 or something. difference in compression is 10.2 and 10.4.

Dirt Freak

Total posts: 219
posted June 26, 2001 01:38 AM
racer4, What I have done in the past to correct the piston weight is change wrist pins......I have done this in motors where I melted one piston and had another laying around say going from a .030 to a .040 with a heavy piston you can run a thin wall pin...I would be running a thin wall pin with the compression being that low anyway.
If you know this ahead of time you can order the right pins with the pistons at no extra charge..........this information may not help you this time.......but maybe next time. Or it should help someone else going down this road soon.

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