Need help fabricating exhaust manifolds

[aerosam]

Thanks guys, some great ideas there. I'll have a chat with the guys in the milling shop in work, otherwise I'll get a holesaw for my pillar drill.

I wish I had the skill to make a full set of tubular manifolds out of SS, i realy do.

[davidimurray]

Aerosam - the setup you are proposing is less than ideal to be honest with you. If you can, individual runners with much longer primary lengths will be better. Have you calculated your pipe diameters, not sure on your engine size, but too big is as bad as too small as it reduces the exhaust gas velocity. Hope you don't mind me commenting. If you want some info on exhaust design and calculations drop me a PM with your email address and I will forward it to you.

Cheers

Dave

[aerosam]

Hi David,

the engine is a 3.0L V8 so each manifold is flowing exhaust gases for 1.5L of engine.

I'd love to be able to make something more suitable but I don't have the skill necessary to do it myself, nor the funds available to pay somebody else to do it for me.

I'll send you a PM shortly.

[aerosam]

forgot to mention, the reason I'm using 2" dia pipe is because that's what was on the donor.

the BMW manifolds looked very constrictive as they all bent sharply down to follow the contour of the engine to allow it to fit in the engine bay of the 5 series. Some were even very squashed across the cross section as the crossed over eachother.

I just want something to get it going for now, and maybe upgrade when funds allow.

[raceral]

I am not sure if you are finished your exhaust or not, but thought I would post a few photos of what I did, it might help or be of value to someone later down the road.
In the case of my V6 I picked up a header gasket and made a template out of 3/8 steel for some header flanges. I cut the circles out with a hole saw on my drill press and hacksawed/filed the rest into shape.
I then welded up some tubes using 1.5 inch tubing, in my case I had some .083 dom tubing and I also am fortunate to have a tube bender. Though you can buy bends.
I then just tacked welded the tubes together bringing it all into a 3 into 1 collector, from there I necked down to 2 inch and using a V clamp exited the body to the muffler which is a reverse flow round tube.
In my case I didn't exit the body with individual tubes because I will be running clamshells and didn't know if having the exhaust exiting right underneath might affect them or the paint.

The drivers side took about three days to do because of clearing the steering column and such, but the passenger side was much easier as it took about 6 hours to do.

It is not a difficult task I would recommend to anyone to try to do their own if possible. Even if you can buy a complete exhaust it is not cheap.
Doing it myself cost me about 150 dollars or roughly 60 0r 70 pounds.

Al

[davidimurray]

Lovely looking exhaust there raceral. Did you buy your collectors in? So far the cheapest 4-1 I have found in the uk is about £50-£60 which seems ridiculous for a bit of pressed stainless!

[raceral]

I bought the collectors a few years back and paid about 8 dollars each or around 5 pound if my conversion is accurate. I would imagine they are more now, not much ever goes down in price.
The header tubing was about 40 dollars or around 25 pound.
The flanges I am not sure as it was scrap I had, I didn't pay much for it.
The 2 inch side exhaust pipe on the was 32 dollars or about 20 pound and the mufflers were 50 dollars for the pair or around 32 pounds, assuming my conversion is close, another 32 dollars (20 pound) for stainless V clamps.
I guess a little more than the 150 bucks mentioned earlier, closer to 170 dollars.
It was one of the more fun parts of the car as far as build goes.

Al