Opinions on Aluminium exhaust manifolds

[62 Dart Convertible]

Saw these on eBay. Aluminium versions of Max Wedge exhaust manifolds. I like the weight saving idea, but I would think there is a reason exhaust manifolds are not normally made of aluminium. Like they would crack. Or melt. Or crack, then melt....

Opinions?

Link - http://www.ebay.com/itm/Dodge-Plymouth-60s-Era-Max-Wedge-Alum-Exhaust-Manifolds-/371219763000?pt=Vintage_Car_Truck_Parts_Accessories&hash=item566e6c0f38&vxp=mtr

Pics -

 

[rscurtis]

JMHO, but I would suggest that they were made for drag racing applications where they are subject to a very short heat cycle.

 

[lewtot184]

pontiac tried it back in 62 or 63. they melt. if you can keep the exhaust gas temps down they might live for awhile. perhaps they're some new hi-temp alloy?

 

[62MAX]

At what minimum temp would expect them to start having problems ? My original cast iron average around constant 395* with very little variance between cylinders.

 

[daniel_depetro]

That is awesome. I wouldn't trust them, but what an idea.

 

[krowbar]

I wouldn't use them. They could distort from the heat and cause leaks at the head. IMHO.Never saw aluminum exhaust manifold before. If you try them let us know how they work.

 

[lewtot184]

At what minimum temp would expect them to start having problems ? My original cast iron average around constant 395* with very little variance between cylinders.

i think alum melts at around 1100f. exhaust gas temps at WOT will reach 1000f+. the cast manifolds on my 69 r/t run 700f+ during normal driving. i'm sure for the price they're chinese so who knows what the alloy is. i wish it was doable to really use those but they're probably only trailer queen friendly.

 

[Cranky]

Cast iron is higher....2200 iirc......and yes, the alloy content will make some difference.

 

[Longroof]

They make Aluminum Cylinder Heads and Aluminum pistons and there is a whole lot more bang and heat goin on inside the combustion chamber... guess it comes down to the type of aluminum used for the manifolds... Why not just get some headers though??

 

[HT413]

They make Aluminum Cylinder Heads and Aluminum pistons and there is a whole lot more bang and heat goin on inside the combustion chamber... guess it comes down to the type of aluminum used for the manifolds... Why not just get some headers though??

Cylinder heads are water cooled.

 

[Longroof]

That's true, but the pistons are not. Exhaust temps can be 1300-1500 ish...

Anyone know what combustion chamber temps are? I have no idea?

 

[Cranky]

They make Aluminum Cylinder Heads and Aluminum pistons and there is a whole lot more bang and heat goin on inside the combustion chamber... guess it comes down to the type of aluminum used for the manifolds... Why not just get some headers though??

Pistons transfer a lot of heat into the cylinder walls and the oil helps cool them too along with the fresh charge of fuel and air. The aluminum exhaust manifolds will probably work ok but maybe not for extended runs on the highway at high speeds....?

 

[HT413]

That's true, but the pistons are not. Exhaust temps can be 1300-1500 ish...

Anyone know what combustion chamber temps are? I have no idea?

True, but only the piston face sees the heat. The aluminum face is able to transfer that heat very quickly to the rest of the piston and to the much cooler cylinder walls. So the piston never sees the full 1000+ degrees.

In fact, I was reading that the piston face never sees that full temperature either, as there is a thin layer of slightly cooler combustion gas that insulates the face.

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Pistons transfer a lot of heat into the cylinder walls and the oil helps cool them too along with the fresh charge of fuel and air.

And that...

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Check this out. Check out how tensile and yield strength drops with temperature. Now, this is for wrought aluminum, NOT typical piston and head alloys, but it serves its purpose. I'm guessing the manifolds won't melt, but they have little chance to seal for very long.

 

[lewtot184]

pistons may see 500f+. they're not only cooled by heat transfer to the cylinder water jackets but also by the intake charge. when pistons melt it's because of too much oxygen in the a/f mix. exhaust ports are surrounded by water, and alum heads will melt down if overly exposed to combustion temps. the only thing that cools the exhaust gases is ambient temps.

 

[tallhair]

nothing to contribute but impressed by you guys knowledge

 

[Cranky]

nothing to contribute but impressed by you guys knowledge

Well, do you think we're all a bunch of do maases?

 

[HT413]

By the by, aluminum exhaust manifolds are more popular in the marine industry because they can externally or even internally water cool them. Even then, iron is preferred.

 

[Photon440]

Here's a 42 year old Pontiac with aluminum exhaust that hasn't melted off yet http://www.hotrod.com/cars/featured/hppp-1210-1962-pontiac-super-duty-catalina/ however I do remember reading about these manifolds in the '70s and how they wouldn't work for oval track racing because of the melting problem, and because of that there was a factory bulletin stating that they were for sub 14 second runs only.

 

[moparsteve636]

Too bad they won't work on a street car! Weight savings would be great for a drag car for sure! There is a problem with them for sure other wise mother mopar would have made them back in the day! I'm sure they thought about it! Be neat wall art in the man cave!

 

[Longroof]

We're ruining a perfectly good bs session with facts now. Haha. Seems more likely they would warp to the point of being useless at sealing before anything else goes wrong... interesting they used them on the Pontiac SD motor though.... they sure we're doing all kinds of experimental fun stuff then though!!