General intake manifold question

[Atrus]

This isn’t really Spridget specific, but I am going to be (or attempting to) be fabbing up an intake manifold for my EFI conversion. I’ve opted to use 18 gauge exhaust tubing to do this.

My question is, what (if anything) would I need to do to the I.D. to resist corrosion? I figure I can paint the exterior or have it coated. What about the interior?

Will the gas mixture keep it from corroding, and I do need to coat it, would a ceramic coating hold up? I see some paints/coatings that advertise “gas resistant”, but I’d think the interior should be “gas-proof” as it’ll be in constant contact. The other thought I had was that coating used to line gas tanks, but I don’t know how thick or uneven it’d be. I obviously don’t want to have a thick coat and want it to be smooth as possible for airflow optimization.

Any experience or theories?

 

[Morris]

Use aluminum.

You can use a braze such as this https://www.aluminumrepair.com/ to hold it together. You can buy idividual sticks of this on eBay for about $3 a pop. If you have a good welding supply shop in your area, you may be able to pick up something comparable for less. You can pick up a very small oxygen/mapp torch at Lowes for about $50.

 

[Atrus]

Morris, where do you get aluminum tubing with some mandral bends? I'm doing the single TB, so the plan was to use some 180* mandral exhaust tubing for a nice gradual radius into each port.

 

[Morris]

Not sure on that one. Maybe you could fill your tubing with sand and bend it yourself.

The easiest way to do it would be to have a staight shot from your head into a plenum.

 

[jlaird]

Tis my understanding that smooth inside intake manifold is not all good. Rough mixes the fuel and air for optimial burning.

 

[Atrus]

Jack, I can see that point, but I think there's an optimal point. I'm also going on the assumption (and I could be wrong) that a FI setup would need less of that than a carb'd application as the injector sprays a finer gas mist than a jet.

 

[jlaird]

I am only repeating what Vizard says about intakes. Do not polish, he did not say do not clean up casting burrs and such.

 

[Atrus]

Oh, agreed Jack. What I meant by the gas tank coating being too thick/rough is I don't want chunks in my intake . I've never seen or used that junk before. 80 or 150 grit sandpaper surface is fine with me on the ID.

 

[jlaird]

yep, would never put anything in there that would come loose.

 

[Glen_B]

Hi Kevin,

Go ahead and use the mild steel exhaust tubing. I've done it for several minifolds and the gas doesn't seem to cause any problem. I used mild steel for the adaptor that joins the turbo to the SU, and for the post-turbo intake manifold and it has NO corrosion at all after years. As always, real experience trumps theorizing and guessing. Go for it with confidence.

Are you putting EFI on a spridget? Megasquirt? I've thought of doing the same since I'll only have to inject one point just ahead of the turbo.

Glen Byrns

 

[Atrus]

Hey Glen,

Thanks for the reassurance. I'll take your word for it and give it a whirl. Worst case scenerio, I can remove the manifold and find a suitable plating at a later time.

Yup, the plan is to do a TBI setup on it. I'll probably be running 2 injectors (although also considering a single setup, that's my next planning obsticle). So, yes, I too will be only injecting at one point.

It'll probably be a little while before I have this functional, just planning and working on it here and there. No real rush.