Need some input on exhaust manifolds

little luke · Sep 19, 2012

Ok. It seems all after market manifolds I've seen are stainless and billet, and the stock are cast. I'm big on DIY projects. And soon as I get my intake buttoned up I would like to start on exhaust manifolds, my question is can you use steel? Anything besides rust being an issue?

DBQLSC · Sep 21, 2012

Figure i'll chime in. I love other people's diy projects to see how they turn out. You could use steel, but with out it being coated, the acid in the exhaust will start eating at it quickly. Cast holds up considerably better in a high heat acid environment. I haven't found a ceramic coating that I'm happy with for sticking to stainless because nothing really wants to stick to stainless, but it could be better with steel. Make your welds all full pen. to hold up to heat cycles. Any weld that is a fillet, needs to be welded on the inside also. Back file welds for stress relief. Have fun you'll be there awhile. I weld stainless pipe for a living and it takes me a considerable amount of time to do a set of manifolds. 52 welds total counting roots and caps seperate. But, they are all top quality welds, no short comings.

little luke · Sep 21, 2012

Thanks for the advise. No, I'm not big on the idea of ceramic coating with the possibility of sending it through my turbo. Ive never had an issue welding cast, but I'd rather deal with stainless. New questions. I can get food grade stainless 90s. What would be the thinnest wall tubing I should use? Second, for chits and giggles, would cutting out the tops of the stock manifolds, porting and working the insides leave the walls too thin? If I could come across a stock manifold cheap enough I'd do it just to see what can be done.

fordboy11 · Sep 21, 2012

opcorn:

DBQLSC · Sep 24, 2012

Sanitary fittings will probably be fine as long as your egt's dont get too high. Mine were designed with 2000 degrees for 30 sec. repeated times. As far as the stock ones, it depends on how far your going to take it. I'm gaining a 1/4" in all directions, so to take a stock manifold that far would be impossible with out adding lots of material.