Jbarker
Active Member
Hello all
Let me start by saying thanks for all the advice on my previous posts. Much appreciated!
The question today is when I reassemble my .030" over 383 based 489 stroker, should I put it together with the dished pistons that I already have for a 9.8 to 1 compression ratio using .039" gasket or spring for flattop pistons which would make it 11 to 1. To make it 11 to 1 (and not higher) I would need to use a thicker head gasket (.051" or thereabouts). Motor is completely tore down at this point, and things such as head gaskets and camshaft have not yet been purchased. There was minor scuffing on the piston skirts and some loss of the crosshatching on the thrust faces of the cylinder walls so I had the pistons polished and the bores honed. Machine shop said the fit was still good. The block is zero decked. I have 440 Source CNC'd aluminum heads. This is a street car and must absolutely run on pump gas. It's not difficult for me to find 93 octane.
The obvious question is if 11:1 is too high for a pump gas aluminum head engine. The secondary question is what are the chances that the pistons I buy will fit the bores that have already been honed? The pistons in question are all 440 source.
Lastly, I can't use a .039" head gasket if I go with the flattop pistons because that would push my compression ratio to 11.3 to 1 which I think is asking for trouble. But going with the thicker head gasket and flattop pistons to get to 11 to 1- is that just a dumb idea since I would simultaneously be increasing the quench height? I know that if I want to get away with higher compression I need a tight quench.
It seems to me that 9.8 to 1 is it touch low for aluminum heads and 11 to 1 is pushing the envelope a bit for pump gas. Your thoughts?
Let me start by saying thanks for all the advice on my previous posts. Much appreciated!
The question today is when I reassemble my .030" over 383 based 489 stroker, should I put it together with the dished pistons that I already have for a 9.8 to 1 compression ratio using .039" gasket or spring for flattop pistons which would make it 11 to 1. To make it 11 to 1 (and not higher) I would need to use a thicker head gasket (.051" or thereabouts). Motor is completely tore down at this point, and things such as head gaskets and camshaft have not yet been purchased. There was minor scuffing on the piston skirts and some loss of the crosshatching on the thrust faces of the cylinder walls so I had the pistons polished and the bores honed. Machine shop said the fit was still good. The block is zero decked. I have 440 Source CNC'd aluminum heads. This is a street car and must absolutely run on pump gas. It's not difficult for me to find 93 octane.
The obvious question is if 11:1 is too high for a pump gas aluminum head engine. The secondary question is what are the chances that the pistons I buy will fit the bores that have already been honed? The pistons in question are all 440 source.
Lastly, I can't use a .039" head gasket if I go with the flattop pistons because that would push my compression ratio to 11.3 to 1 which I think is asking for trouble. But going with the thicker head gasket and flattop pistons to get to 11 to 1- is that just a dumb idea since I would simultaneously be increasing the quench height? I know that if I want to get away with higher compression I need a tight quench.
It seems to me that 9.8 to 1 is it touch low for aluminum heads and 11 to 1 is pushing the envelope a bit for pump gas. Your thoughts?