oversize pistons
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From: venus texas
oversize pistons i was looking for oversized forged pistons for a 4.8 liter engine... the engine has 340,000.. still runs but i would rather rebuild it now... thinking of a turbo build later so i need strong pistons.... i want at least 550whp.. the engine is going in a 71 240z... also looking for a t56 in the dfw area..
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From: BFE
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From: venus texas
yep the 4.8 has a longer rod which makes it harder to find... how long would it last if i turbocharged it with stock assembly but replaced the bearings?? sometime or later i will build a 6.0.... how much will a typical rebuild cost?? i usually build 351, 302, 460, 350, 454...
I bought some Speed-Pro's cast hypereutectic 4.8L .030" over-sized for My 5.3L and They list them as having the same compression height as the 5.3L stock and after-market slugs but I'll be dipped if they are'nt maybe .020" lower so I'm milling the deck down .023" so I can have My quench at .035"-.037",,,,,,,kind of a pain in the ___ . 1 person told Me they thought that over-sized pistons normally have lower compression heights ,,,,how much depending on how much over-sized they are for reasons of keeping the compression the same ,,,,,,,but that does'nt sound right to me ,,,,,how can You plan You're engine out with certain parts if they did that ?
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From: venus texas
how much did they cost? did u rebalance the crank, rod, piston, combo?
I bought some Speed-Pro's cast hypereutectic 4.8L .030" over-sized for My 5.3L and They list them as having the same compression height as the 5.3L stock and after-market slugs but I'll be dipped if they are'nt maybe .020" lower so I'm milling the deck down .023" so I can have My quench at .035"-.037",,,,,,,kind of a pain in the ___ . 1 person told Me they thought that over-sized pistons normally have lower compression heights ,,,,how much depending on how much over-sized they are for reasons of keeping the compression the same ,,,,,,,but that does'nt sound right to me ,,,,,how can You plan You're engine out with certain parts if they did that ?
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Verdad Gallardo Well I guess not at $180 for the set at summit . They're probably a little more now . As far as balancing , I removed some weight from the undersides of each piston and a little from the inside of the pin ends and they all are within 1/2 gram +/- of each other and they all weigh, I forget exactly, something like 3 grams more with ARP Sportsman rod bolts than the original piston, rod, pin, rings and rod bolts and the engine will only see 6000rpm's once in a while .
Yes Rezin Texas , 5.3L LM7 pistons have a 9cc dish at least that's what I measured and the 4.8L do have flat tops and both are listed both from GM and all the aftermarket parts I've seen as having the same compression height .
On a side note, the speed pro pistons I bought had a compression depth .010 lower than stock. I'm told this is because the piston manufacturer compensates for people having to deck the block for flatNess is A stock rebuild.
It makes it easier for people who just slap their **** together, but a pain in the *** for people who actually plan. It's even worse that they advertise it as stock compression height.
