350 rebuild/ piston weight calculation right or wrong?

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tchapps88
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350 rebuild/ piston weight calculation right or wrong?

Post by tchapps88 »

spun a rod bearing on my 1990 L98 shortblock in my monte carlo, decided not to go to a 383 since i was happy how it ran before it ate itself and after a fb marketplace find and some internet research this is my plan, got a vortec 305 in running condition that i will use the crank and then also it has the newer style PM rods which will get arp bolts for extra insurance. From what i found, 305 cranks and LT1 cranks are supposedly balanced almost identical so I want to use oe style LT1 pistons which the factory ones are reportedly 532g.

I found on Rock auto for $200 a set of mahle 2243497 pistons with a pin height of 1.56 vs the stock 1.55, called mahle tech support trying to find a weight to see if they are close to the factory pistons and they only list a weight for std pistons and i plan on going .030 over. Std bore weight is listed at 503 grams, a .030 over piston is 0.75% larger so by that calculation the weight would round to 507 grams in theory. does that sound close?
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Re: 350 rebuild/ piston weight calculation right or wrong?

Post by PackardV8 »

tchapps88 wrote: Wed Nov 30, 2022 12:15 pm and i plan on going .030 over. Std bore weight is listed at 503 grams, a .030 over piston is 0.75% larger so by that calculation the weight would round to 507 grams in theory. does that sound close?
It doesn't work that way. Oversize rebuilder pistons are the same weight as STD bore. Trust, but verify; a balance is always a good investment.
tchapps88 wrote: Wed Nov 30, 2022 12:15 pmspun a rod bearing on my 1990 L98
So it ate that rod journal so badly it can't be reground undersize?
tchapps88 wrote: Wed Nov 30, 2022 12:15 pmit has the newer style PM rods which will get arp bolts for extra insurance.
Early forged or later powdered rods, either will require reconditioning the big ends.
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Re: 350 rebuild/ piston weight calculation right or wrong?

Post by BillK »

I think the first thing I would do is get one of the 305 pistons off the rod and weigh it. Then you have something to go by. You have to be careful with the catalog weights too. A lot of times they are for the piston only.

I wouldn't waste my money on ARP bolts. The dirt track guys around here run the PM rods with the factory bolts and really do not have any problems.

Also, Unless my catalog has a misprint I think that 224-3497 is an LS piston ? The Mahle number for the LT1 piston is 224-2810
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Re: 350 rebuild/ piston weight calculation right or wrong?

Post by PackardV8 »

The best feature of PM rods is the bolts aren't removed for recon. Just make the hole larger for oversize bearings. Faster, easier, better.
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