Anyone good with exhausts?

[stulane]

Hi,

I've fitted my new engine (m50) and its basically all ready to go, just one big problem, the exhaust. the manifolds and downpipe need to be modified and im not having any luck with them.

What sort of welding equipment would i need?

Also, whats the deal with welding cast? Is it just not going to happen?

Is there anyone in the south east who can help? If anyone can make the manifolds for me, im happy to pay, just want the car on the road - sounds like a monster truck:)

Is there anyone in the south east who can come and have a play?

Thanks,
Stuart

[Jos]

You can stick weld cast iron but you need special rods for it. It's nearly impossible to weld, it has a tendency to crack and you have to all sorts of stuff to prevent this. Heating the whole lot up to 800C then doing small 1" welds, then insulating it to stop it from cooling too fast. Even at that it can still result in small cracks around the weld, which is no good for a manifold.
There are a few other methods as well, none of them easy though, get someone to do it who has welded cast iron before. The cooldown is more important than the actual welding.

The downpipes are easy, they are not cast and are just normal steel, you can weld it with anything that you can get the current down low enough with, DC Arc, MiG or TiG.

What do you need to change on the manifold?

[stulane]

Hi,

Thanks for the advice.

The engine is an M50 from an e34 so the exhaust doesnt fit around the steering column. The manifolds need to be cut and new pipes need to be added to make it fit around the steering. I've got e36 downpipes as well. it just all needs to be cut and welded to fit onto my 325 e30 system.

I'm gonna have to ring round tomorrow but i was hoping someone on here might be able to help, there usually is someone here that can solve a problem.

[koos]

Hello mate, I'm in crawley, up the drag. Try see if a proper engineer could fabricate you a branch(manifold) and then get exhaust guys to make the rest, try use a common flange so it's easy to match the down pipe,I know of a good engineering place in Horsham area if you are interested, chow.
Mitch

[stulane]

Hi Mitch,

Sounds like a plan. The main prob is that its best to have the car when making any parts as you need to measure the clearances.

If i can find someone who has already made the manifolds for their conversion, maybe i can pay them to give it another go??

..then off to the exhaust place or give it a try myself, if its just steel i can prob find a mate to help. i think the cast problem is the biggest challenge.

[Jos]

get some of that flexible 2" aluminium tubing and do a mockup with it, then take that to the engineering place along with the existing manifold so they can do the outlet holes and mounting plate properly.

[glenn]

forget trying to weld the cast manifold, for the reasons jos has given you.
easier to get someone local to make you a new manifold.
if you wanted to do it yourself you'd probably find the mig the easiest to use on such thin material

[Jos]

So does anyone have any info on how to actually design an exhaust manifold lol?

[koos]

Bit of spit some twine and a leatherman!!!! hey McGiver

[johnono]

toilet tube rolls and some sticky back plastic

[stulane]

toilet tube rolls and some sticky back plastic

Sounds like a plan, i think i can manage that.

[johnono]

jus kiddin fella , the manifold trick is, all the pipes need to be the same lenght this means the gasses flow at equal pressures or summin? then the lenght of the actual pipes are important too, the longer they are the better, but i dont know why

no sharp bends and usually 2 sets of 3 into 1 pipes if u get what i mean..

some manifolds

[stulane]

So it gets more complicated...

First you have to get hold of the pipes

Then you have to design the manifold to fit around the steering

And then, you have to make sure that the manifolds are all the same size and as long as possible.

I'm thinking i need to find someone to help me.

Anyone on here good at making manifolds??

[Jos]

and it gets even more complicated....

Pipe length is determined by what rev range you want to get the gains in
Pipe diameter is based on displacement, valve size and cam timing.
Then you have the secondary pipes that are matched so the wave pulses create a standing wave to draw gasses away from the exhaust valves, then the collector size, entry angle, diameter etc..

loads of fun... not a simple thing really, and then yes you have all the issues with the steering too.

Enjoy lol..

and no I have no idea how to design one, just been trawling the web for a couple of hours, dunno the maths for it, although I might go get a book

Oh and those little X-pipe things are seriously cool for engine power..

[6potWil6pot]

Hey my old M50 manifold looked welded if im not mistaken!

Was completely unbalanced since it was a 2 and 4 split, sounded pretty meaty tho!

[Jos]

The one on my M30 was welded too, didn't say it couldn't be done, just it's really really f*ckin hard to do right.

I wouldn't attempt it, not worth the effort, the sucker will just crack again.

[stulane]

Can i get away with cutting the manifolds only where they join onto the downpipe?
Someone else on here i saw cut the maifolds at the start closest to the engine and then rejoined them but that would be a lot of work and effect the manifold workings?

That would keep them pretty standard and i'm trying to get hold of a set of steel manifolds from a 328 so that would make life a lot easier.

I recon if it was just joining steel pipes i could get someone to help.

[Jos]

If you have to cut the manifold itself, then you are going to have to weld it again.. see above. Is there no way the manifold fits without mods, forget about the downpipe for the moment, if the manifold does fit on it's own then you can just make a downpipe that matches up. If the manifold doesn't fit then you are back to square one I am afraid..

[stulane]

i've got some steel manifolds from a 328 coming but my question was, can i get away with only cutting the manifold at the bottom or do i have to also cut out a section nearer the engine side?