Flange Choice for Exhaust Build

So I'm in the process of building my bundle of snakes. I borrowed a friends Iceengine header design kit and am working away. I was trying to put everything together with one piece header flanges on each side but for a number of reasons I would like to cut the flange into individual pieces for each port. Does anyone know of a big down-side to going this way? The engine is a Ford 363 Windsor and the heads have the 3" bolt spacing. The flange will be 3/8" thick.


Randy V

There’s no down-side that I’m aware of.
As a matter of fact, I think that the seal of the flanges would be better that way.

Bill Kearley

Gold Supporter
On a 40 you must have a flange for each pipe, I wish I had 3 inch heads, room for a a 2in. exhaust and looks great. keep an eye on clam fit over pipes.
My 302 V8 exhaust has a single one piece flange either side and it works fine. The only minor issue is clearance to get a couple of the socket head bolts in. I had to thin down a couple of the bolt heads. The exhaust has been on and off a couple of times and once after running the engine and everything continued to line up and seal against the gasket. Importantly, from a visual point of view, the two pipes continued to exit dead central through the rear body aperture. I’d be concerned that without ‘anchoring’ the pipes to a single flange you will have assembly and alignment issues.
Just my 5 penny worth!
Roger Allen


Bronze Supporter
Kim, a brand new lessons learned from my exhaust build: try to build as low as possible in order to keep as much distance as possible to the rear clip. I used single flanges also, which also makes the build much easier.
Kim, the separate flanges should be fine, have done it that way myself. One recommendation, use flanges that are as thick as possible. Think I may have used 3/8th last time I made a custom manifold. 1/4 might be OK but in my experience thicker is better. You might be surprised how much a flange face will flex/curve under point loading.

Related, I've found that crushed copper gaskets work best for individual flanges. Just my $.02.
Use the one piece flange, set everything up and weld, then split the flange would be my process. 4 into 2 into 1 with the 1 being a very large muffler with 6" inlet/outlet and straight through if you could fit it. That will sound awesome and be surprisingly quieter then you imagine.
Thanks for the input everyone! I finished the exhaust. Turned out great! All primaries are within an inch in length of each other and I was able to use one piece flanges. It sits as low as it possibly can. I'll be building heat shields for the transaxle and rear of the intake. The pipes will be eventually wrapped in titanium wrap. Best of all, every spark plug can be changed blindfolded, they are that easy to access! I used the Iceengine design kit and then cut and tacked it all together, built a jig and had Manuel at JMD Tubes TIG weld everything.

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Looks awesome. Can you have someone make a template of the thing for others to duplicate?

There are so many variables to each build I doubt this exhaust would fit other applications. Where the motor sits and the angle, the port height on the heads etc...along with different clearances for transaxles would make it impossible to successfully duplicate and fit. I now know why Fran only makes exhaust systems custom for each vehicle.