Making exhaust manifolds

[husker]

I am building a custom car and using a 95 3.4 to power it. I cannot use the original style exhaust manifolds or original style headers as they interfere with the foot well as they exit toward the rear of the engine. I cannot flip them from side to side as there are issues with the alternator and power steering.

I cannot find any block hugger / shorty type manifolds that would exit at the center port so I had a thought to make my own - a thought which usually gets people into trouble.

I am thinking about a building a manifold/header using steel fittings from McMaster-Carr. a few elbows, along with some 12" seamless steel tube in 1¼”, and a 1¼ - 3 reducer ought to do it for each side. The flanges can be bought in both 3/8 and 1/2.

So... thoughts on this wild hair? Right now the engine is stock, but the future holds cam, pistons, etc... I am aiming at 250 hp (or more). Making the manifolds would certainly assist in adding a turbo as there is not an 'off the shelf' turbo manifold for this application.

[hockeyman]

Re: Making exhaust manifolds

My question is:
If you're custom building an engine, WHY a 3.4?? If your aiming for 250 hp, why not a rebuilt 3.8, or even better...a V8?

[husker]

Re: Making exhaust manifolds

The car is based on an Opel GT... and the only engine that I could find to fit between the fenders is a 60 degree 6v (or a straight 4 - but that was not an option). A v8 would add pounds to the extreme front end and all are 90 degree which will not fit.

[husker]

Re: Making exhaust manifolds

Now I am thinking of a log-type manifold similar to stock ones... just made in the configuration that I need, which is exiting anywhere but near the rear. Two elbows (first and last cylinder) nad a "T" (middle cylinder) sounds easy. The exit would be in the middle so it would not interfere with anything. Log-type manifolds are a far cry from equal length headers but 1 1/2 ID should flow better than stock atleast.

[hockeyman]

Re: Making exhaust manifolds

My opinion: The hard part is bending the pipes right where the manifold meets the engine and makes a hard turn downwards.
I'd take a 1/8" piece of flat steel and configure the manifold's flange first, then begin the pipes to where they would all meet at the same point. You've got some pretty nasty work ahead of you though. This kind of stuff isn't for amateurs.
Are you welding the pipes yourself? If so, what kind of welder are you using?

[husker]

Re: Making exhaust manifolds

I can purchase exhaust manifold flanges in either 3/8" or 1/2" thick. From there I would weld a 90 degree elbow to the exhaust port closest to the firewall and have it exiting facing the middle port. I would do the same with the front port and have it face the middle port also. The middle port would have a "X" fitting that would pick up the middle exhaust port and the two elbows on either side. This diagram below does not do it justice but it may help get a visual.

I I__ __I I__ __I I
I____ __ __ ____I
I I

I would do the welding. If I used the steel pipe I would use a mig. If I went with thinner tubing, I would use a tig.

[ma4life]

Re: Making exhaust manifolds

Sounds like you got it figured out pretty well, I hope it works out for you. If you can, take some pics for us to see. My only sugestion would be: since you're already building your own, you might as well engineer them a little better to get some decent flow. What's a few more minutes of time now, than replacing / remaking them later. Good luck and keep us posted.

[AZ3.8Camaro]

Re: Making exhaust manifolds

Have you looked into maybe finding fwd manifolds for that engine? I know for the 3.8 the fwd and rwd manifolds are different, they might suit your needs, but I don't know.

[husker]

Re: Making exhaust manifolds

In my attempt to source some tubing for the forward swept exhaust manifolds I am thinking about making, I visited a muffler / exhaust shop nearby. I was talking with the guy that does all of the custom exhaust for the company about tubing size and other considerations when he told me to follow him into a back room. He told me not to tell the management what he was about to tell me. He told me to go to Home Depot and buy their 1.5" chain link fence tubing and use that for the headers. He said it is the same stuff they use in making custom headers and much cheaper than buying it through the exhaust shop. He said to simply grind off the zinc/galvanized coating and weld away.

Is this quy for real? I have had to weld galvanized stuff before and have simply ground it off near the weld. I have never had a problem with the weld being strong doing this but it never crossed my mind to use fence tubing for exhaust. I have a tube bender and can certainly handle bending the fence piping to any desired angle I want.

For the collectors he told me to stretch some 4 imch tubing... place the 3 exhaust tubes into it... tack weld the tubing to where they touch... and then hammer in the 4" pipe until it forms a collector shape around the 3 exhaust tubes...then weld a bead all around.

Using fence tubing for the exhaust and making the collectors actually sounds like it would work but it also seems kind-of half a$$... Thoughts?