header welds at flange?

[olddog]

I took my header and side pipes off. I'm going to do away with the slip joints and weld flanges in. I was pleased to find the heads have the exhaust ports perfectly matched to the gaskets. The header flanges were nicely matched to the gaskets, as well. However when the pipes were welded onto the flanges, the welds flowed into the pipes restricing them.

There was lots of variability. The sides were the worst, and the tops and bottoms were pretty good. The worst weld was about 1/4" and the best was 1/8." I would say half of the pipes had been narrowed by 3/8" by these welds. Anyway I decided to grind them out and smoot them up. I hated to grind up the Jet Hot coating. I have a good ceramic paint, and will be welding the flanges on anyway.

So do you think this will make a noticable improvement in the HP department?

347 stroker should be 400 hp, by desktop dyno. My main motivation was to even up the cylinders flow since it is multi point fuel injected.

[Three Peaks]

The best headers are welded on the inside of the flanges then ground down flush so you don't have any restriction on the inside or obstructions or unsightly weld on the outside. You can do the same thing on the header-to-sidepipe flanges. Just tack the flanges in place from the outside on each pipe, take the header/sidepipe joint apart and weld them on the inside then grind down the weld for best flow.

That is how I was shown by Len Ewell and it worked out great on the headers I made and the sidepipe flange connection.

If you have that much restriction at the head exhaust port, you probably have some turbulence building up at that point and costing you some horsepower. Hard to determine how much unless you do a before/after test.

Bob