Exhaust port and HE diameter

Mark McClure · 02-11-2006, 04:03 AM

OK so I though that I had everything sorted out with my heads. UNTIL........I mated the SSI's up to the exhast ports to check studs lengths.

The heads have had a lot of work done to them and it looks like the PO has, among other things flared the exhast ports out from 35mm to 40mm. So the situation is that the SSI's will now create a step of 5mm.

What is the concensis on this...leave as is or flare the SSI's out to 40mm. I do not know if this can be done or not without effecting the integrity of the joint. Any advice would be most welcome!

Thanks

Mark.......

Mark McClure · 02-12-2006, 03:14 PM

Bump.....

Had another though on this yesterday.......If I chamfer the SSI' out to 40mm then the wall between the inner pipe and the flange will be revealed, maybe causing leak issues. I will check later today to see exactly were the welding is between the flange and pipe. If it is all around the outside then things may be OK..your thought please.

Thanks

Mark.....

Mark McClure · 02-15-2006, 07:10 PM

BUMP.....any advice would be much appreciated?

Tyson Schmidt · 02-15-2006, 08:08 PM

This is exactly why I recommend against using SS!'s on 3.2's. The 3.2 has 38mm exhaust ports, and they also step out to 40mm to facilitate the gasket protector portion of the stock HE's. So when you use SSI's which have no gasket protector, you end up with a giant step.

It sounds like you're in the same situation here. I definitely wouldn't alter the SSI's. Just run them the way they are. It will cost you power at the top-end, but the engine will run strong anyway. There are plenty of people out there running SSI's on 3.2's and they're very happy with them. It's definitely not ideal, but they work.

Mark McClure · 02-15-2006, 08:31 PM

Tyson,

Thanks for the advice. You are right about the 3.2. This engine previously had a 3.2SS conversion and has now become more of a b******d then before due to the change back to 3.0 before I bought it. I do not know what pipes they ran on it before, may have been 3.2s.

Would you cut the gasket back to 40mm to remove the risk of creating a burn scenario which could potentially extend to the outer edge, or leave the exposed gasket?

Cheers

Mark....

Tyson Schmidt · 02-17-2006, 09:32 AM

Use the 3.2 gaskets from a stock 3.2 engine. That way they are already the right size to match the port in the head.

BReyes · BReyes's Garage

So there is a step from my exhaust port (38) to my SSI's (40)? Hmmm. Had SSIs on my 83 SC too (i supposed they were different size on the SC SSIs).

I also have another 3.2 in process (I am beginning the smoothing of the ports), and I need to determine the size of the header (TT) flange. Now where is that box?

Regards,

Tyson Schmidt · 02-24-2006, 09:51 AM

Quote:

Originally posted by BReyes
So there is a step from my exhaust port (38) to my SSI's (40)? Hmmm. Had SSIs on my 83 SC too (i supposed they were different size on the SC SSIs).

I also have another 3.2 in process (I am beginning the smoothing of the ports), and I need to determine the size of the header (TT) flange. Now where is that box?

Regards,

No the 3.2 exhaust port ends up effectively being 40mm due to the recess for the flange protrusion on the stock HE's.

So you end up with a 40mm port feeding into a 35mm opening.

It's fine on a 3.0, since they all had 35mm exhaust ports.