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Question asks gvw. Often higher gvw vehicles received a lower compression motor. But sometimes it was just a cam differenceHuh? cant tell my looking at piston what RPM it's rating for....
what I have would be called dished or flat?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.
then my current engine would be low emission, wouldn't it? it was replaced some time in the past.That looks like a flat top piston - higher compression than the usual dish ones.
it could explain the smell from the exhaust and some pinging noise.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