Tig welding stainless manifold help

[Phataz1]

Ironmonger, thanks! The manifold is for use of motorbike carbs on a car. Yeah I have seen the method you are talking about before, isn't it quite common to do that on exhausts? I would have done that but it'd require a pipe bender which I don't have, and some pipe the right size. I found stainless tubing so difficult to find in anywhere near the right size so I had to make do with 2mm oversize, and thats why it has been done with this method. Definitely something I'd like to try in the future though :-)

Cheers,

Arun

 

[ironmonger]

Manifold

Hi Arun

Yeah been there also, tube size wise. My current avocation, amongst others, is blacksmithing. That often leads me to form things in a different, less conventional manner.

You could form that cone from sheet as well. In the piping industry we often form square to round sections, and even stainless steel forms more easily when it is heated. if you layout all the parts with a piece of thin cardboard you can mock up the entire piece and when it 'fits' both the square end and the tube size open it up and cut that shape from sheet then form it and weld the seam. That will get more welding practice as well.

The method of welding of the exhaust manifold, as you mentioned, is common. We also try to maintain a smooth flow into the head as well. While fabricating a smoother flowing tube system for the intake side might be something to try later, the best part is proof of concept and a running engine. Pretty can come later.

I thought of doing something similar to a 1600 Kent engine from a Ford pinto that I have installed in a 1972 Spitfire body that I picked up. The previous builder overhauled the engine... but forgot to torque the rod bolts. The poor old 1500 only lasted a few miles... good for me 'cause I got it for the price of a haul-away.

How have you addressed the higher fuel pressure from an automotive system being applied to the motorcycle carbs? That is one reason that the
Spitford project has not gone any farther... aside from a lot of other projects...One good thing about hobbies is that if you get tired of looking at something you needn't feel any guilt about putting it aside and starting something else.

Paul

 

[Phataz1]

Ahh yes, I forgot about the sheet forming method! I have seen that in practice before but I never even thought about doing it myself! The ports are oval on this engine so in my simple brain I only thought of heating and crushing round tube to match lol, yes you could get a much more accurate match by forming it from sheet. I'll probably use that method if I ever have to do any more complicated ones!

There are a few methods to decrease the fuel pressure, I run bike carbs on my own car I have used a low pressure electric fuel pump (originally a mechanical pump) and a pressure regulator. Apart from that all that is needed is jetting to suit, and then balancing/needles ect adjusting. It runs very well when set up properly!

The method used by the people I am making these particular manifolds for (who have the high pressure fuel injection pumps), is simply to link the fuel supply pipe to the fuel return pipe with a T-peice, and use the spare outlet to feed the carbs. So it basically feeds the carbs from the back pressure! Most people report good results with this method but some people discover too much or not enough fuel is supplied, which I think is due to the fact that the formation that the pipes are attached to the T-peice makes a difference.


Thanks,

Arun

 

[Phataz1]

I can see a clear improvement since my first attempts, still some undercut to improve upon, what do you guys think?

Thanks,

Arun

 

[Steve182]

Well done mate, looking good now, the undercut can easily be solved by forcing a little more filler rod in, it just stops the weld from being concave.

 

[Ink fabs]

Hi there i am a pipe welder, it looks like your making good progress with the welds but just a word of warning i would be going around the flange last as that is the easiest pipe welding to do.

 

[hotrodder]

I can see a clear improvement since my first attempts, still some undercut to improve upon, what do you guys think

MUCH better, massive improvement!

Re the undercut...


Most of it is from losing the torch angle (circled in red, the shape of the weld freeze lines is the tell tale) which'll typically result in an increased arc length.
Adding wire more frequently will help too, really want an overlap of 70-80% on filler additions i.e. rather than pushing more wire in add small amounts more frequently. If you look at the pic Langy posted earlier the freeze lines are much closer together

 

[tigler]

I agree with previous comments about using stainless or in fact any steel for an inlet manifold. The reason is too much thermal inertia. Steel will heat up and cool down slowly and this will cause problems with engine warm up then hold too much heat when hot.
Also it is unnecessarily heavy, but thats the racer in me talking !

 

[Phataz1]

Yeah I understand that now, it makes sense. I'd prefer to use ali from now on anyway as is much nicer to work with. Just gotta get better at welding it lol.


I was asked to do these manifolds in stainless so thats why I'm using it. They are very heavy and very difficult to manipulate I agree!

Thanks to everyone for the comments

Arun

 

[Phataz1]

Just thought I'd update this with the latest manifold I'm part way through. I feel there's a massive improvement even since the last time I posted on here. Its amazing how over time you pick up little tricks and methods without really realising it!

Obviously not as good as some of the guys on here, but I'm mega chuffed as beforehand I might have got a single lucky weld, but now I'm able to be pretty consistant :-)

 

[Delgado]

Just thought I'd update this with the latest manifold I'm part way through. I feel there's a massive improvement even since the last time I posted on here. Its amazing how over time you pick up little tricks and methods without really realising it!

Obviously not as good as some of the guys on here, but I'm mega chuffed as beforehand I might have got a single lucky weld, but now I'm able to be pretty consistant :-)

Looks like you're getting more consistant. There are several different schools of thought on this, but I'd be inclined to follow the previous advice from HR about filler addition.

really want an overlap of 70-80% on filler additions i.e. rather than pushing more wire in add small amounts more frequently.

Also, bear in mind that you only need the leg length of the weld to be equal to the thickness of the thinner of the 2 materials that you are welding together. I mean, if the tube is say 2mm WT then you could go a bit smaller with the weld, which in turn will put less heat into the material and give you less distorsion to worry about (amongst other things).