DIY Water cooled Exhaust manifold?

[SPARK1]

Is it possible to make your own water cooled exhaust manifold? Could you weld one up from plate and pipe? Has anyone done this for a engine in the 5-8 liter range?
Also water injected exhaust?(wet exhaust)

[michael pierzga]

Originally Posted by SPARK1

Is it possible to make your own water cooled exhaust manifold? Could you weld one up from plate and pipe? Has anyone done this for a engine in the 5-8 liter range?
Also water injected exhaust?(wet exhaust)

If youre talking aboyt the manifold then it easier to purchase a secondhand unit. If you talking the waterjacket, easy ...every jacket Ive ever used was shop made. Flange on the hot side, heavy wall exhaust steel pipe inside , a thin wall pipe overtop with water nipple and exhaust temp sensor. Have a look on the internet and you will find details.

[Lurvio]

A manifold can also be made, but it is going to be a huge project.

Probably the way to do it, would be to make the inner manifold (if not a factory unit), then make the outer skin separately. Then using a bandsaw or similar tool to split the outer skin and weld it over the manifold. Lot of pressure testing (manifold and outer skin both separately, then final when completed) to get it water/gas tight. A bit of thought has to be given for bolting to engine.

Hope this helps
Lurvio

[michael pierzga]

Yes ...huge

http://www.hitekmarine.com.au/products.htm

[Frosty]

If you think about it its not a big job, they do it all the time here in Thailand.

The manifold pictured above would be a good donor for water injection, a pipe nipple could be welded to each pipe lower than the exhaust valve chamber.

A water cooled jacket would be more like the Mercruiser --a box manifold with a water jacket around it. Usually an inch or 2 of pipe is left open at the engine end ( you go to get the bolts in).

Not performance manifold no--but niether is the bog standard Mercruiser and even if made in 4mm stainless longevity is 5 years tops.

Normally they start with a dummy head on the bench and make the 4 pipe flages and weld to a stout pipe, then bolt to the head. A box is then made and welded up to the pipes (youl'le be glad of the inch or 2).

Personally I would then make a 3 sided box as the jacket for ease of welding straight onto the flat side of the engine side of the manifold.

Where your intakes and outlets are is up to you.

[SPARK1]

What I was thinking was, weld up a manifold using thick walled pipe and T's.
Either a simple pipe to elbow from port one and then just T off to each port in a straight line. Make sure that the pipes from the ports are at least 5 " so that there is room for distorthion from heat. Then take a piece of flat plate about 6-10mm and machine the holes for the pipes. This is the base that will go against the exhaust gasket. Let the pipes stick through slightly and weld pipes to base. Then weld the rest of the box on, you could use thinner plate. Weld on a radiator cap fitting on top as this box will be your header tank as well. Weld on your water pipes. You would have to have pipes going though welded to both ends of box for bolts to fasten to head. when all welding and pressure testing done, then machine the base flat.

Does this make sense?

[Frosty]

Either Iether, not one way of doing it. Thing is distortion one would be suicidal if it did'nt fit the head which is why its best to work on the head itself all the time.
Doing this on a V8 in the boat ,--twice,---Oh I would'nt do it.

One last point I would angle the pipes down to the manifold so if a leak were to appear it would not enter the cylinders before you could get to know about it.,--if you have room.

Might be better to machine the plate and fit to the out pipe before building up the internal t's.

I would not use T's but just one big pipe.

Use thick steel then you can stick weld it, you have to get in some tiny tricky places and if it fks up you will not get a grinder in there.

I assume you a good welder.