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Just about every custom EFI inlet manifold I have read about has been made in aluminium, is there any reason why stainless steel could not be used instead?

 

If I make it in SS, then I could could do pretty much all of it myself, whereas aluminium I would to outsource.

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You could use stainless.  It's a bit harder to work though.  Suggest making the head flanges at least from mild steel.

 

All the manifolds I've made have been from mild steel as it's cheap, readily available, easy to work and easy to weld.  Rust isn't a great issue as they don't get very hot.  The Vitesse one is simply painted and is still presentable after 12 years.  You could also get them aluminium sprayed, powder coated or even (deep pockets!) ceramic coated.

 

Presumably you saw this?

http://sideways-technologies.co.uk/forums/index.php/topic/7048-manifold-fabrication/

 and maybe this?

http://www.shadetreegarage.co.uk/inlet%20Manifold.htm#Top

 

Nick

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Hi Nick,

 

I'd seen the second link, but not the first which is particularly useful. I had totally discounted mild steel, so it's good to know that it's perfectly OK to use, that makes the whole thing so much simpler.

 

One quick question about the design you went for, why did you make the plenum with it narrowing to the rear. That may have been in the thread somewhere, but I missed it, so apologies if it was.

 

Darren

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Plenum tapers to the rear to try and maintain a more even velocity as at the front it needs to flow enough for 4 cylinders, at the rear, only 1.

 

Having said that, didn't do this with my Vitesse one and it seems to work well enough!

 

Nick

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Ok, makes sense. For ease of fabrication I may go down straight cylinder route.....

 

A local engineer is going to make up the manifold flanges for me, he's asked if it's worth doing a run of them as most of the work is in the initial set-up rather than production.

 

Any demand do you think?

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I had 3 sets laser cut locally along with a couple of plenum back plates.  Think it was £ 80 including them doing the drawing.  Sold 1 set to a friend at cost and the other two sets have been turned into manifolds as seen in the thread linked above.

 

I think demand for flanges alone would be small.  Can enquire about getting some more laser cut if you like - they have the drawing now and the dimensions proved good.

 

Nick

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I'm looking at making another GT6 manifold for the spit6.

 

I could do a run of 3 or 4 pretty easily.

 

I'd be happy to do it, but I suspect they'd be costly if I had to pay for the work in them

 

C

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The 4 cylinder ones are different from 6 cylinder unfortunately.......  not even the same pair-spacing.  It's a pain!

 

I need to get the 6 cylinder ones drawn so I can get a few sets made as I'm feeling the urge to meddle with the Vitesse inlet.......  Likely to be wanting steel though as my ali welding is still shocking!

 

Nick

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I had 3 sets laser cut locally along with a couple of plenum back plates.  Think it was £ 80 including them doing the drawing.  Sold 1 set to a friend at cost and the other two sets have been turned into manifolds as seen in the thread linked above.

 

I think demand for flanges alone would be small.  Can enquire about getting some more laser cut if you like - they have the drawing now and the dimensions proved good.

 

Nick

Thanks for the offer, I may take you up on it if my guy can't do it for any reason. I'm doing some work for him, so I can offset the cost of what he does, so is the cheapest option hopefully.

 

I have a spare cylinder head to help with measurements etc., but it's the other side of Devon at the moment. Can you you recall the ID of the inlet port/runners?

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The reason many custom inlet manifolds are made in aluminium is that it's easy to work with. It's malleable - you can easily bend, stretch or shrink aluminium tube, and it's easy to machine and file. Also, commercially available manifold parts, such as injector pockets and throttle body flanges, are usually made from aluminium. Yes, aluminium requires TIG welding, but I think stainless steel does as well?

 

I had some head flanges made by water jet cutting:

 

post-638-0-68668000-1465083382_thumb.jpg

 

Attached is a pdf of the head flanges. I wish I had a dxf version, but the pdf can probably be turned into a file for a profile cutter: Flange plan.pdf

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Stainless steel can be MIG welded (even with steel wire, though will corrode).  In fact it is also possible to MIG weld aluminium, but very difficult - especially difficult to get it neat.

 

TIG will give a neater, less porous result with either but aluminium requires AC TIG - which is expensive.  The pros say TIG welding aluminium is easy, easier than stainless.  This has not been my experience so far.  Need more practice!!

 

Nick

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I had 3 sets laser cut locally along with a couple of plenum back plates.  Think it was £ 80 including them doing the drawing.  Sold 1 set to a friend at cost and the other two sets have been turned into manifolds as seen in the thread linked above.

 

I think demand for flanges alone would be small.  Can enquire about getting some more laser cut if you like - they have the drawing now and the dimensions proved good.

 

Nick

 

Hi Nick,

 

Do you think your guys would let you have a drawing so I can just forward to the guy doing mine? A bit cheeky I guess, but would ensure a good fit and save time.

 

Cheers

Darren

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I had 3 sets laser cut locally along with a couple of plenum back plates.  Think it was £ 80 including them doing the drawing.  Sold 1 set to a friend at cost and the other two sets have been turned into manifolds as seen in the thread linked above.

 

I think demand for flanges alone would be small.  Can enquire about getting some more laser cut if you like - they have the drawing now and the dimensions proved good.

 

Nick

 

 

 

Hi all

 

Nick if there is enough demand and you  decide to get some cut I could be interested in a couple of six cylinder inlet flanges in aluminium. Going with carbs at the moment but definitely want to fuel inject the Vitesse and GT6 in the future. Depends on what they are going to cost.

 

thanks

 

Mark

Edited by Mark

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Here you go Nick You might want to check that it converted properly.

 

You will need to download it and rename it as a .DXF file. The forum wouldn't let me upload it as a .DXF file.

attachicon.gifFlange_Plan (DXF not TXT).txt.

 

Thanks James, a dxf should load into most laser or water cutters, so the file is a good resource for the forum.

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All the steel is arriving next week to make the manifold, it was so cheap it wasn't much more to have the whole 6m lengths for the runners & plenum, at least that means I'll have plenty spare to practice on.... :yes:

 

Being out in the sticks means there's not that many choices on where to get the flanges made, the 2 places that could laser cut have a 2 month waiting list, so have found a local guy that can make by hand.

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On 6/4/2016 at 6:51 PM, GT6 Nick said:

The reason many custom inlet manifolds are made in aluminium is that it's easy to work with. It's malleable - you can easily bend, stretch or shrink aluminium tube, and it's easy to machine and file. Also, commercially available manifold parts, such as injector pockets and throttle body flanges, are usually made from aluminium. Yes, aluminium requires TIG welding, but I think stainless steel does as well?

 

I had some head flanges made by water jet cutting:

 

post-638-0-68668000-1465083382_thumb.jpg

 

Attached is a pdf of the head flanges. I wish I had a dxf version, but the pdf can probably be turned into a file for a profile cutter: Flange plan.pdf

GT6 Nick, thanks so much for posting this drawings, you have no idea all the time you saved me. Just wanted to thank you in public. This is a great forum, thanks for all the knowledge. 

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Thanks Alfredo. The pattern is made from a scan of a GT6 inlet manifold, with connecting pieces added to improve stability.

It’ll pay to check the dimensions before you get metal cut, as some US heads (in TR6s anyway) had different port spacing. The story I’ve heard is that the port spacing was altered to prevent US owners fitting UK petrol injection manifolds back in the Seventies. The PI system gave much better performance, but US cars had Stromberg carbs. One reason I’ve heard is that its emissions were too high for US regulations, possibly because it didn’t include altitude correction. Or, the PI setup needed to be worked on by trained technicians, and British Leyland didn’t want to risk problems in the US where there would be few specially trained mechanics.

That said, my GT6 was originally US-spec before being shipped to Australia, and its port spacing is the same as UK cars.

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Port spacing thing is true and seems to be later US TR6 related though I've never seen anything definitive written. The possible reason makes a sort of sense I suppose, in a paranoid, bureaucratic sort of way, so that's probably right too!

If they were worried about emissions from PI systems, and clueless meddling with it, they were right to be, as amply proven in the UK market over many decades.  Doesn't need to be altitude related either, though it certainly doesn't help!

Nick

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Thanks so much, this will be for my 69 US spec GT6. By looking at my manifold the dimensions seems to be correct, I will double check any way before having them cut. 

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