Head/header dilemma

[adf5565]

I think I got myself into a sticky situation. Had the 350 for my 72 C20 with 4 speed rebuilt and put on aluminum AFR heads which have a square port. About 1.4” square. I had purchased hedman headers previously with the “added” clearance for the clutch cross shaft.

Engine is back in the truck and I’m installing the headers and just realized they are round port style. Supposed to be 1-5/8 primary’s but at the flange the best I measure is 1.5”, and in many cases is smaller due to flange interference. Thus I am going to get a somewhat restrictive mismatch between the head face and header.

How big of a deal is this? I’d purchase something else but it is difficult to find a header that fits all of my requirements (square port, clearance for the clutch, etc). Anyone have recommendations for different headers?

Picture shows the extent of restriction to a square port gasket which matches very closely to the head itself.

[HO455]

It's not the worst case scenario. Installed as is you may have leaks. If that isn't an issue you may have some slight reversion issues that may not be noticeable outside of plugs running a darker color.

One bandaid fix would be to get a thick header flange(3/8"-1/2") that matches the smaller round tubes and grind the the square side out to make an adapter to help the transition. Kind of like a square bore to spread bore carb adapter. It require longer bolts and it would move the headers out towards the frame and that may cause interference problems.

Or if you're handy with a welder you can remove the round flanges and replace them with square flanges.

[adf5565]

Originally Posted by HO455

It's not the worst case scenario. Installed as is you may have leaks. If that isn't an issue you may have some slight reversion issues that may not be noticeable outside of plugs running a darker color.

One bandaid fix would be to get a thick header flange(3/8"-1/2") that matches the smaller round tubes and grind the the square side out to make an adapter to help the transition. Kind of like a square bore to spread bore carb adapter. It require longer bolts and it would move the headers out towards the frame and that may cause interference problems.

Or if you're handy with a welder you can remove the round flanges and replace them with square flanges.

Thanks for the input. I've also realized the flange for those headers is very sloppy and blocking part of the tubes as is. I'm going to clean that up as best i can which will help and remove some of the restriction, and I believe the gasket should match the header so I'll get a round port gasket instead.

Being that most aftermarket heads have square exhaust ports I'm surprised there isn't more options available but i guess it must not cause too much of an issue

[70STOVEBOLT]

I have never seen square tube headers, but if the primaries are 1 5/8 they should work fine as-is. It does look like the flange is oddly shaped in the pic, I hope the tube is not the same shape as the opening.

[adf5565]

Originally Posted by 70STOVEBOLT

I have never seen square tube headers, but if the primaries are 1 5/8 they should work fine as-is. It does look like the flange is oddly shaped in the pic, I hope the tube is not the same shape as the opening.

Yep they are 1-5/8. For being hedman headers I’m not impressed at the quality, some of the flanges have 1/8” obstruction in the tube. Which I’ll try to clean up. Thankfully the tubes themselves are round at least.

[70STOVEBOLT]

I have Hedders on my truck and they seemed pretty good, but I would like to see a thicker flange. I bought the unpainted version, looks like you did too.

[MikeB]

Yeah, square up those round openings as much as possible. Otherwise, there will be exhaust gas blockage and turbulence.

My Hedman 62010 stainless headers used the gaskets below which matched the header ports. And the width was near perfect for the 1.35" square ports on my heads. So the header tubes were >100% open to exhaust ports.

[adf5565]

Originally Posted by MikeB

Yeah, square up those round openings as much as possible. Otherwise, there will be exhaust gas blockage and turbulence.

My Hedmans used the gaskets below which matched the header ports. And the width was near perfect for the 1.35" square ports on my heads. So the header tubes were >100% open to exhaust ports.

What model header did you use? I saw they sell some with the oval ported flanges which would match the heads a lot better. I Just wasn’t clear how much the clutch shaft would interfere.