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Discussion Starter · #1 ·
I have a ZZ 383 and was thinking about changing the pistions from the Hyper's to Forged and wanted to know what all I would need to do. I've had the motor for two years now but it is still new on the engine stand. I was thinking about superchargering or NOS and forged is the way to go.
 

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Depending on the amount of boost or the amount of N2O, why not keep the Hypers? If you aren't adding a bunch of sauce, you'd be fine. Spend the money and enthusiasm on more important stuff.

DON'T detonate. But you shouldn't do that anyway, no matter what pistons you use.
 

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If you're going to NOS it, forged are cheap insurance to prevent catastrophic failure if it does detonate. If you burn a forged piston, it will still go up and down in the bore. THe hypers are more likely to end up in the oil pan with the rod flailing away in the block. All you should need to do is hone the block with a deck plate to the specified clearance.
 

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I have a ZZ 383 and was thinking about changing the pistions from the Hyper's to Forged and wanted to know what all I would need to do. I've had the motor for two years now but it is still new on the engine stand. I was thinking about superchargering or NOS and forged is the way to go.
Man we almost have the same set-up ( '69, TKO, Currie & SBC ) Forged is always better in a NOS or blown application. Good insurance. I say go blown but that's just me. You could even do a procharger to keep it under the hood. Me I like the nasty roots blowers.:yes:
 

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i dont know why someone would tell you to not put forged pistons in a motor that will see any amount of nitrous or some type of forced induction. Hey i got an idea lets put a trans brake in a stock tranny and see what happens leaving at 5 grand????????? IMO
 

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Install the forged pistons. Its as simple as remove old and install new.
Remember: Its better to have what you don't need, Then need what you don't have!
 

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Discussion Starter · #8 ·
So I should be able to reuse all the main bearings right. The motor has never been fired so I could just mark them put them right back in. Who makes a good forged pistion? Also right now the compression is 9.6-1 so what would be the best way to lower it at the same time.
 

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Check the weights - if they differ by more than a few grams, you'll want to have it rebalanced. Other than that, sell the hypers to help with the forged purchase.
 

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i bet pistons for that will be spendy. unless someone makes off the shelf replacement forged pistons for it, they are gonna have to be custom pistons- GM got to 383" by using a stock 4" bore with a 3.8" stroke, where most 383's are built with a 4.030" bore with a 3.75" stroke.
 

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Discussion Starter · #12 ·
I going to have to check but I think your right about the 3.8 stroke. I also think I read somewere once that GM used a 4.005 pistion. I'm not sure but it could of been piston slap or something it was a couple years ago.
 

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I just finished grenading a 454 this past weekend going through the traps at about 6800.

The timing chain let go. #2 exhaust valve was hit first, which disintegrated the hypereutectic piston which then took out cylinder #1. Half of cylinder #1 and half of cylinder #2 is gone. The rods are in several pieces. Only about half an inch of rod is attached to each pin. Similarly about a half inch of rod is attached to the big end. Amazingly the steel crank survived, the billet cam survived and both oval iron cylinder heads.

Will I ever again use a hypereutectic piston ? NO

The block thrust was worn badly and so was the back of the cam sprocket. It was thrusting badly against the back cam plug. No doubt misalignment of the cam and crank sprocket caused the chain to let go.

Will I ever run a used motor without first disassembly to check? NO
 

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did it have an HV/HP oil pump? What was the hot idle oil pressure at what RPM?
 

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I just finished grenading a 454 this past weekend going through the traps at about 6800.

The timing chain let go. #2 exhaust valve was hit first, which disintegrated the hypereutectic piston which then took out cylinder #1. Half of cylinder #1 and half of cylinder #2 is gone. The rods are in several pieces. Only about half an inch of rod is attached to each pin. Similarly about a half inch of rod is attached to the big end. Amazingly the steel crank survived, the billet cam survived and both oval iron cylinder heads.

Will I ever again use a hypereutectic piston ? NO

The block thrust was worn badly and so was the back of the cam sprocket. It was thrusting badly against the back cam plug. No doubt misalignment of the cam and crank sprocket caused the chain to let go.

Will I ever run a used motor without first disassembly to check? NO
Breaking a timing chain at 6,800 RPM will cause major damage regardless of what piston you used.
 

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Yes HV oil pump over 60 psi and I have a big red low oil light on the tach by the shift lift that comes on at 20 psi.

Agree major damage, but the hyper piston in #2 just disintegrated and then took out #1.

Partially not fair to blame some components of the short block, but with forged pistons the damage would have been reduced considerably, probably limited to the one cylinder.

Cleaned up and magnafluxed the heads and they are OK, amazing when you look at the block, what is left of the pistons and rods.
 
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