Anyone built an aluminum exhaust?

[jt1]

Everytime I pull the exhaust off my car I'm amazed at how much it weighs. I haven't weighed it but I'd guess it at 50-60 lbs. It's dual 2 1/4 into a single 3 incher. It's got me thinking about an aluminum system. Lighter, no rust. Would the exhaust gases corrode the AL? Is their a source of AL tubing and bends? Does anyone have any experience doing this?

[johnc]

Since aluminum melts at ~1,200F and noticeably softens/elongates at ~800F I would think the exhaust system would have problems staying together.

[Oltmann]

Originally posted by jt1:

Thanks John, I hadn't considered melting point being a problem. It would be a complete bummer to fab up a system and it melt and fall off. Heads and pistons are AL though and they do fine. Maybe because they are cooled by the intake charge? Anyway, I'll give it some more thought. I've got some grass burners laying around from my dirt track days, maybe I'll try them on the Z.

 

John

Al pistons are alloyed with copper, zinc, and silicon to withstand the temp. Unfortunately the alloys used are very susceptible to corrosion, especially when welded.

 

If you could cast your entire exhaust out of the stuff, that might work

[johnc]

Pistons are also cooled by oil.

 

Exhaust gas temps are generally 1,300+ degrees in the header primary pipes but drop considerably by the end of the collector unless the header is coated or stainless. Try thin wall 304 stainless. You can also try to find some aluminum alloy tubing (5356 or 6061). I assumed you were talking about 1100 (pure) series aluminum.

[Guest Anonymous]

Some of the AL alloys tend to get real brittle when welded. 6061 for example likes to crack if its not welded with great care, even then its a crap shoot at least from what I remember reading off Kent Whites great site. Best deal, save the aluminum for a custom aluminum intake manifold, now your talking!

 

Regards,

 

Lone

[johnc]

You can TIG or MIG weld 6061 with 4043 filler and be pretty much assured of no cracking. But the weld area will lose at least 30% of its treated strength. For example, T6 will fall back to at least T4 in the heat affected zone.

[jt1]

Thanks John, I hadn't considered melting point being a problem. It would be a complete bummer to fab up a system and it melt and fall off. Heads and pistons are AL though and they do fine. Maybe because they are cooled by the intake charge? Anyway, I'll give it some more thought. I've got some grass burners laying around from my dirt track days, maybe I'll try them on the Z.

 

John

[fl327]

you could always go titanium, and if youre really feeling rich-oval 4" all the way back.

[Drax240z]

6061 will weld nicely and strong if you prep things right. Remove all surface oxidation and contaminants, and heat it up a lot before welding. If you try to weld without pre-heating you'll get cracks most likely, as the weld will cool too quickly. (the rest of the object will pull the heat away from the weld unless its allready up to a similar temp)

 

Half our FSAE car is 6061-T6 and we've had no issues with our welds at all. (including major stress pieces like uprights, caliper mounts, pedal box, etc)

 

One thing that does suck with 4043 filler though, is you can't anodize it after!

[zgeezer]

Cast aluminum headers? Yeah, I think Pontiac provided a set with some of their super duty 389/421 in 1961 or thereabouts. The heads, cam, intake manifold, and aluminum exhaust manifolds all came packed in the trunk. I've seen them on the bench, but never actually installed. I wonder if there are any hard core Pontiac muscle car preservationists out there that might actually have a set.