Standard port is not a big deal. U will just need adapter plate.
Standard stuff really going to large tubes on sbc stuff.

 

Could you explain a little better. What do you mean I will need an adapter? I've found a set of header flanges that are 1/2 inch thick for standard port heads and a 1.875 OD tube diameter. The 1 1/2 schedule 40 elbows are 1.900 OD so a touch of grinding and they will slip right in place and weld up nicely.

 

The pipe will not be a perfect round.
Adapter plates have been used fir years on sbc with large tubes.
You will know u need them once you build the header.
If you can not get the 2 middle bolts in adapter us need.

The adapter plate just bolts to the head and allows you to have a different bolt pattern and still keep large tubes in an sbc.

 

These are adapter plates. Flat headed bolts go in the stock location, and your header is mounted over them. The header is bolted into the 7 bolts that are away from the port.

 

And these are spread port exhaust ports. It is obvious once you see them. They actually come with the 7 bolt pattern. Another option is having your heads tapped for the 7 bolt pattern. Just make sure whoever does the work is certain there is enough meat there.

 

The holes in those adapter plates look extremely small and restrictive.


I thought the whole point of spread port heads was to make the exhaust port spacing even like that of a Ls head?

 

Those holes are small. Those are small adapter plates. I have larger ones that are "D" shaped I can take a pic of for you if you would like.

The spread port was actually to make a straighter shot for the exhaust increasing the flow (thats what I have heard). They can never be like an LS engine due to the center exhaust valves being next to each other.

You don't have to do a spread port design, I would just think it would be easier making the headers. The 6 bolt design is deffinately harder. I didn't do the 7 bolt route when I made my headers, and I am not happy with them. I am very picky though, so I am not surprised I am not happy. Lol

 

I'll throw a micrometer on my old hedman long tubes tomorrow and see what the primary OD is. As is the bolts were accessible on them but I wouldn't want to get much tighter.

 

They holes are small on the adapter plate because u need to port them so they match the exhaust ports shape and location.

 

Alright I'm itching to order up some schedule 40 stuff. Did we decide on 2 1/2 for the log and 1 1/2 for the primaries? FWIW the heads I'm looking at have square ports so that may help with the header bolt issue having square instead of round ports. They are AFR 235 eliminator competition heads.