Using steel for intake manifold?

[1985ShlbyChrger]

Would it be ok to use steel for a custom fabbed intake manifold? I don't want to hear everyone saying use aluminum. I just want to know why it would/would not be a good idea to use steel. It will be heat barrier coated after it is fabbed. I cannot weld aluminum, so I want to use steel. What thickness should I use? I've got some ideas on what I want to do, just need a good reason to not use steel, other than it will get hotter quickly(which is why it will be coated)

So the question I would like answered are these:

What thickness should I use?
Will it rust on the inside if it is not stainless?
Will coating it work for keeping heat from getting to the charge air?

Thank you

Nate

[BadAssPerformance]

Back in the day intake manifolds were cast iron so steel might work. Stainless would be the only way to go for longevity and thermal issues. Other than weight, the biggest issue with steel with be thermal expansion vs. the aluminum head which may make it difficult to seal with boost.

[1985ShlbyChrger]

Well I was thinking, since the exhaust manifold is cast iron, shouldn't the intake seal just as well. Then I realized that there isn't 20 psi running through the exhaust manifold. I guess I could try it and see. I may just go with the aluminum and have it welded, but I'd like to do everything myself.

[GLHS592]

Your aluminum cylinder head bolts to your cast iron block...

[puppet]

Well I was thinking, since the exhaust manifold is cast iron, shouldn't the intake seal just as well. Then I realized that there isn't 20 psi running through the exhaust manifold. I guess I could try it and see. I may just go with the aluminum and have it welded, but I'd like to do everything myself.Steel shouldn't be a problem at all.

[WVRampage]

I dont see why steel would be a problem other that its heavy,but then again the weight in over the front wheels so it may not be a thing.It would rust on the inside if not coated,but if you were talking of having it coated in some way but I dont think that would be that hard to do.I noticed no one here has comented on thickness.

[Pat]

It's going to be very heavy...you might want to make up support brackets to help support those typically weak intake/head bolt threads and/or use studs.

[turbovanman²]

The only issue I can see are weight and rusting on the inside. It would need to be stainless but the type that doesn't rust, I didn't know this but not all stainless is rust proof, my boater buddy told me this. Or have it powercoated if not using stainless, as I would think over time, regular paint will come off, especially if using alky.

[BadAssPerformance]

Well I was thinking, since the exhaust manifold is cast iron, shouldn't the intake seal just as well. Then I realized that there isn't 20 psi running through the exhaust manifold. I guess I could try it and see. I may just go with the aluminum and have it welded, but I'd like to do everything myself.

Cast Iron and steel are different material entirely when it comes to thermal expansion. Welded thin wall steel vs. thicker wall cast iron (cuz it has to be thicker to cast) are night and day when you talk about heat effects.


Your aluminum cylinder head bolts to your cast iron block...

It is also head on with 10 M-11 Bolts and a much stronger gasket than the manifolds use


It would need to be stainless but the type that doesn't rust, I didn't know this but not all stainless is rust proof,

"300" series (304, 316, 321, etc) stainless a.k.a. "true stainless" is rust free. other versions like 409, 410, etc rust on the surface. This is what our "stainless" OEM mopar exhausts are made of and why they rust.

Welding aluminum is not that hard and a nice intake manifold project would make for good practice :thumb:

[WVRampage]

Now what about making a tubular intake that looks like a header with the TB on the colector?

[glhs875]

Well I was thinking, since the exhaust manifold is cast iron, shouldn't the intake seal just as well. Then I realized that there isn't 20 psi running through the exhaust manifold. I guess I could try it and see. I may just go with the aluminum and have it welded, but I'd like to do everything myself.

There is more pressure (turbo'd) in the exhaust than in the intake. The thinner while still being strong enough, is the better for an intake. Less material for heat soak. A sheetmetal intake cools better/quicker from the air moving inside of it than a thicker cast type intake. Steel, like exhaust tubing or similar should work really well!!

[glhs875]

The only issue I can see are weight and rusting on the inside. It would need to be stainless but the type that doesn't rust, I didn't know this but not all stainless is rust proof, my boater buddy told me this. Or have it powercoated if not using stainless, as I would think over time, regular paint will come off, especially if using alky.

I've been using exhaust pipe for intercooler tubing for many years. Rust is not a problem.

[t3rse]

I paint the inside of my i/c plumbing

You can MIG aluminum! give it a shot! (get the right gas and wire and make sure you purge the inside of what you are welding as well as the outside) I imagine that you are afraid of TIG welding...which will take some time to get good at if you have never done so before...

[turbovanman²]

I've been using exhaust pipe for intercooler tubing for many years. Rust is not a problem.

Are you running alky? if so, it will rust.

[puppet]

Now what about making a tubular intake that looks like a header with the TB on the colector?The air intake demands made by the cylinders at higher rpms require a plenum.
It's like an air tool powered by a small tanked compressor. Under heavy use, the compressor will not be able to keep up with the tools demand. In order for this to work best, if at all, you'd need a huge collector with four(4) individual TB's ... one for each cylinder.

It's the "ideal" intake set-up for a couple of reasons but unfortunately it would be a real PITA to implement.

Alcohol by itself won't rust steel ... it's actually used as a vehicle in a few rust preventive applications. A guy could use nitrate solutions to treat the steel ... like blueing gun barrels.

[BLUEBALL]

Doesnt seem that rust would be a problem. Old school cars that had steel intakes and stayed out of water had no issues. Of course runnin alkyhol may possibley show some rust/corrosion around injector bungs. But most likey if puddles were left behind. Weight? Welding real thin sheetmetal may be just as much a job as learning to TIG weld. Its not terribly hard,you just gotta have the equipement to start. Another thing that may be an issue is a mounting flange. At least with aluminum you can hack it off a stock intake.

[BadAssPerformance]

Yes, getting the injector bungs the correct location, etc would be way easier to steal from a stock manifold.

Getting all welds to seal is also a concern, pressuretesting is a must no matter what material it is made out of.

[glhs875]

Are you running alky? if so, it will rust.

Yes, and haven't noticed any rust on the only pipe the alky contacts. I just recently had it off to make a new larger diameter piece. The old one was clean. I'll keep an I on it though. I run straight alky, no water, if that makes a difference.

[puppet]

Cast aluminum intakes are easier to produce. Number one reason aluminum is used. Sheet aluminum is easier to work with than steel. ... but it ain't better. Steel is better at insulating from and storing less heat than aluminum.
The steel mani could weigh more and still out perform the aluminum in absorbing/dissipating heat. Stainless is king here ... and polishes nice too.

Porting might be an issue though :/

[BadAssPerformance]

I've never run alky but the water probably does make a difference when it comes to rust.

[1985ShlbyChrger]

I wasn't even thinking about MIG welding it. I forgot about that route. I think that I will go with the aluminum then. I was thinking about going with the stainless but I guess it's gonna cost just as much as the aluminum will.

Thanks for the ideas guys. Let's kep this thread going and see what else we can come up with.

Nate

[turbovanman²]

Yes, and haven't noticed any rust on the only pipe the alky contacts. I just recently had it off to make a new larger diameter piece. The old one was clean. I'll keep an I on it though. I run straight alky, no water, if that makes a difference.

I run a 50/50 mix and I have rust spots inside my stainless tubing so thats why I mention it. I can't imagine what would happen to cast iron, can you say Titanic, :lol: