who makes the headers for the aluminum 113 corvette heads? i'm thinking you have to mod the flanges by ovaling mounting holes. anybody know? they have a raised exhaust port and angled plugs...just to make things difficult..

 

you can use any thirdgen header, though i'm running the hedman longtubes. no modifications necessary.

 

should i use the larger tubes? 13/4"?...it looks like the openings won't match up.....you sure?

 

1-3/4" is a BIG header for a 305, unless its got some sort of power adder on it. The openings would match up just fine, a SBC is a SBC. The only difference with the 113 heads is the D-shaped exhaust ports, but that shouldn't cause any problems as far as headers go.

I'd suggest using a 1-5/8" header on your 305 though. 1-3/4" is not really going to be worth the extra money unless you actually need the extra breathing capacity, or plan to change to a larger motor later (ie. 350, 383, 400...)

 

the heads are going on a 350....

 

1-3/4 would be good for a 350, and they should cover the D-ports just fine.

 

i'm positive, this is the combo i'm using and have been 12.16@110mph babying it out the hole with MUCH more to gain. a 1 3/4" header will gain you nothing but a lighter wallet unless your running bigger cubes (383+) or a power adder of sorts.

 

hedman just gave me part # 68309 for the heads......don't know much more.

 

look at hedmans part listings, they make D port specific headers.

 

The centerline is also raised .100" higher than the bolt holes. I have these heads and I know. Any standard 1 5/8" header will just barely clear, as long as you grind out any welding slag from the inside. A better choice is a 1 3/4" header. Think about it. People will say running larger valves on your heads is a good idea, for example 1.60" exhaust valves, so why would you then restrict it with a 1.625" outside diameter header? Also, hot exhaust wants to expand. Giving it a larger path to exit will be beneficial.

 

makes sense, kevin....was there space on the flange to elongate the holes? i was thinking of doing that the centerline is just 0.10 off...