SC Exhaust Port Size

sigchuck · 02:11 PM

Hi guys, I'm trying to use a set of headers on my SC from a 930, which I think has countersunk heads like the 3.2 Carrera. I've read an SSI Installation thread where the poster states he used 3.2 SSIs (with the extra pipe sticking up past the mating flange) on his factory 3.0 heads by tapering the portion of extra pipe down to a bit over 38mm.

If the SC head is really 38mm at the mating surface, I should be fine with the headers I have, but the Bruce Anderson book indicates ALL SC heads were 35mm though. Does anyone know for sure? Is the 35mm measurement just the diameter at the combustion chamber and it tapers out as it gets to the mating surface to a but over 38mm? Does anyone have an unmodified head they could take a quick measurement on?

Thanks for your help! I'd love to get this sorted out before I'm in the middle of the install!

EDIT - I should have mentioned this is being done in conjunction with a turbo conversion, thus the 930 headers.

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by sigchuck

Hi guys, I'm trying to use a set of headers on my SC from a 930, which I think has countersunk heads like the 3.2 Carrera. I've read an SSI Installation thread where the poster states he used 3.2 SSIs (with the extra pipe sticking up past the mating flange) on his factory 3.0 heads by tapering the portion of extra pipe down to a bit over 38mm.

If the SC head is really 38mm at the mating surface, I should be fine with the headers I have, but the Bruce Anderson book indicates ALL SC heads were 35mm though. Does anyone know for sure? Is the 35mm measurement just the diameter at the combustion chamber and it tapers out as it gets to the mating surface to a but over 38mm? Does anyone have an unmodified head they could take a quick measurement on?

Thanks for your help! I'd love to get this sorted out before I'm in the middle of the install!

EDIT - I should have mentioned this is being done in conjunction with a turbo conversion, thus the 930 headers.

There are basically 2 different SC heads. The earlier sets have a flat exhaust 35mm port.
The later SC heads have a 35mm port with a larger recess recess for a flange on the exhaust similar to the Carrera but smaller.
The turbo has a smaller port (34mm?) but the recess for the flange is the same as the late SC.

sigchuck · 02-13-2021, 06:11 PM

Thank you, Henry! That’s very helpful. Sounds like my 83 SC should likely not have a problem with the 930 headers then.