critter

iTrader: (9)

I hauled the block, crank, new H beam rods, and new Mahle pistons off to the machinist. After checking it out, he complained that the pistons were unmatched by a total of 5 grams. This surprised me as the Mahle pistons were touted as one of the best. OTOH, I have been out of the game so long that I don't remember how significant 5 grams is. Comments?

PREDATOR-Z

Well, the LS1 is internally balanced after shortblock moc assembly. So unequal piston weight can have negative effects on that and harmonics.

66deuce

iTrader: (1)

i thought Mahle was the OEM supplier for the ls1 pistons?5 grams does seem like a lot,but i'm not an expert.who's doing your machine work?anybody around town here?

critter

iTrader: (9)

Yeah, I don't know whether 5 grams is significant or not. He will equalize everyting, of course. I sort of remember wanting to get everything with 1 gram, but my memory is dim. Mainly I was surprised at that much spread on a quality piston.

C&P in Fort Wayne is doing the work. I looked around and they seemed to be the most clueful of the places I talked to. One place said "what is a honing plate?"

critter

iTrader: (9)

The machinist will equalize everything. I just wondered why he thought 5 grams was a large spread for a quality piston.

Steve - Race Eng

iTrader: (1)

Five grams is a bit much to machine off the heavy pistons to get them to the weight of the lightest one. There is not a lot of "extra" material to machine. I would send the pistons back and get another set.

Steve

66deuce

iTrader: (1)

LSonederfull

I agree 5 grams is high but arent Mahle pistons inexpensive? I would weigh pins and weight match them to pistons alleviating weight mis match as much as possible, than i would lighten heavy pistons as much as safely possible.
If still off you can lighten pins by grinding inside pin and re polish grind marks to finilize weight match.

PREDATOR-Z

This is why the cost of a set of matched pistons outweight the cost involved in balancing an unneven set.

c5jim

I just sent my rotating assembly to have it balanced. A new set of Mahle pistons,pins and rings were included with the crank, rods and harmonic balancer. The pistons, pins and rings were within 1 gram + or minus for each cylinder. The weight of a stock GM PISTON is 434 grams. The weight of a Forged Mahle piston is 382 grams. That is a weight savings of almost 15 ozs. of rotating mass in 8 pistons. This is the same manufacture for the LS1-LS6-LS7-AND THE C5R. If it is good enough for them, it should be good enough for me. It is not always the price but the quality. This time the price is in favor of the customer.
JIM

critter

iTrader: (9)

That is what he did - mix and match parts to get as close as possbile before any cutting.

critter

iTrader: (9)

Susrprised that yours are so much closer than mine ....

fastsspr

iTrader: (49)

[QUOTE=c5jim]I just sent my rotating assembly to have it balanced. A new set of Mahle pistons,pins and rings were included with the crank, rods and harmonic balancer. The pistons, pins and rings were within 1 gram + or minus for each cylinder. The weight of a stock GM PISTON is 434 grams. The weight of a Forged Mahle piston is 382 grams. That is a weight savings of almost 15 ozs. of rotating mass in 8 pistons. This is the same manufacture for the LS1-LS6-LS7-AND THE C5R. If it is good enough for them, it should be good enough for me. It is not always the price but the quality. This time the price is in favor of the customer.
JIM



I thik nk you did the rigth thing.Just send the complete anssambly to be balance!!!

chpmnsws6

iTrader: (70)

the 4cc 3.905 piston thats built for a 6.125 rod weighs between 384.9 and 386.2 grams. the wrist pins all with EXACTLY the same