New edlebrock Heads
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Joined: Nov 2008
Posts: 8,501
From: Central Fl
Out of Line, Everytime😉
Joined: Dec 2006
Posts: 10,137
From: Melville, Saskatchewan
I knew I saw something about a 4.125" bore size, pulled from Summit's website. For use with hydraulic roller camshafts. Recommended for applications with a minimum of 4.125 in. bore spacing.
https://www.summitracing.com/parts/e...ake/oldsmobile
Will we ever see that 4" bore version Mark and another guy has, who knows.
https://www.summitracing.com/parts/e...ake/oldsmobile
Will we ever see that 4" bore version Mark and another guy has, who knows.
Last edited by olds 307 and 403; Apr 18, 2024 at 05:50 AM.
Registered User
Joined: Sep 2011
Posts: 2,148
From: Plano, TX
It's not the bore, it's the stroke. The "small block" heads just have a smaller chamber to help keep the compression high on the shorter stroke small blocks that might be using stock big-dish pistons. The rest of the head is identical.
Bore spacing is identical on all Olds v8's, big block or small block. Big blocks tend to have slightly larger bores, but not a whole lot. The 403, which is a small block, is the one with the giant bores that require a certain head gasket. Still the same bore spacing.
Bore spacing is one of those fun things where the popular platforms like BBC/SBC the aftermarket has managed to make what are actually entirely custom engines but look kind of like a BBC or SBC. Once you have a different bore spacing it's a totally different engine - different crank, block, heads, almost certainly a different intake and exhaust. OK, might use the same rod and piston design.
So ads for heads will talk about bore spacing just to avoid mistakes because of those few very interesting things.
Then you get into "raised cam" blocks which get even more interesting.
Bore spacing is identical on all Olds v8's, big block or small block. Big blocks tend to have slightly larger bores, but not a whole lot. The 403, which is a small block, is the one with the giant bores that require a certain head gasket. Still the same bore spacing.
Bore spacing is one of those fun things where the popular platforms like BBC/SBC the aftermarket has managed to make what are actually entirely custom engines but look kind of like a BBC or SBC. Once you have a different bore spacing it's a totally different engine - different crank, block, heads, almost certainly a different intake and exhaust. OK, might use the same rod and piston design.
So ads for heads will talk about bore spacing just to avoid mistakes because of those few very interesting things.Then you get into "raised cam" blocks which get even more interesting.
Out of Line, Everytime😉
Joined: Dec 2006
Posts: 10,137
From: Melville, Saskatchewan
I believe he was on one of the Olds Facebook pages. He was testing rocker arms I believe. He may have been FOS but the heads looked right in the pics. That 4.125" bore spacing, which obviously isn't Olds V8's bore spacing is what Summit has in a note on the bottom of the Edelbrock Olds aluminum heads.
Registered User
Joined: Nov 2008
Posts: 8,501
From: Central Fl
I believe he was on one of the Olds Facebook pages. He was testing rocker arms I believe. He may have been FOS but the heads looked right in the pics. That 4.125" bore spacing, which obviously isn't Olds V8's bore spacing is what Summit has in a note on the bottom of the Edelbrock Olds aluminum heads.
A chamber width of 4.125 or so would be the bb heads. Again the small blocks are about 4.00”.
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