Piston identification

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eran tomer

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Hello
Can you tell by this piston if it’s a below 8500 gvw or above 8500 gvw engine?
 

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Schurkey

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IF there's a difference in the pistons, I'd expect the "over 8500 GVW" piston to be dished.

Heck, the UNDER 8500 GVW Vortec 5.7L pistons are dished; as were my original '88 K1500 TBI 5.7L pistons.

The car ('92 Caprice, Roadmaster, perhaps the Camaro/Firebird, for example) 5.7L TBI pistons were flat-top, though. Added about 1/4-point of compression ratio compared to the dish pistons in the trucks.
 

eran tomer

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IF there's a difference in the pistons, I'd expect the "over 8500 GVW" piston to be dished.

Heck, the UNDER 8500 GVW Vortec 5.7L pistons are dished; as were my original '88 K1500 TBI 5.7L pistons.

The car ('92 Caprice, Roadmaster, perhaps the Camaro/Firebird, for example) 5.7L TBI pistons were flat-top, though. Added about 1/4-point of compression ratio compared to the dish pistons in the trucks.
what I have would be called dished or flat?
 

Pro439

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You do not have stock pistons. GM hasn’t used flat tops in years early 70’s high hp engines as they don’t meet emissions and don’t like the low octane gas we have today. I don’t know if they would like the 91 non ethanol gas. It would depend on how big the combustion chamber of the cylinder head is. If it’s an open chamber head you’d be ok but a closed chamber it will more than likely spark knock
 

eran tomer

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You do not have stock pistons. GM hasn’t used flat tops in years early 70’s high hp engines as they don’t meet emissions and don’t like the low octane gas we have today. I don’t know if they would like the 91 non ethanol gas. It would depend on how big the combustion chamber of the cylinder head is. If it’s an open chamber head you’d be ok but a closed chamber it will more than likely spark knock
it could explain the smell from the exhaust and some pinging noise.
This head would be open or closed chamber?

the regular fuel we have here in Israel is 95 RON. there is also 98 RON in some stations that's intended for gaz monkeys.
 

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