Exhaust manifold sag
 

I just read an article by Michael Eisenbise about exhaust manifold replacement with a link to an article by Vince Falter about the cause of sag--my car has the affliction. One factor contributing to the sag is the weight of the exhaust pipe and muffler hanging from #4 cylinder. Has anyone tried an exhaust hanger in front of he muffler to alleviate this issue ?

Re: Exhaust manifold sag
 

The best way to alleviate this very common problem is preventative: Install the manifold gland rings in the exhaust manifold BEFORE it starts sagging. Ford initially used these and then some time in 1929 he discontinued installing the rings, which resulted in manifolds no longer being counter-bored for the gland rings. Predictable warpage occurred in the #4 exhaust port, so Ford re-instituted installing the gland rings. He learned his lesson about drooping exhaust manifolds - and so should we. If you can't get your exhaust manifold to seal using the four gland rings, #4 is most certainly drooping. The only cure is a new exhaust manifold, copper manifold gaskets and GLAND RINGS. Otherwise, a drooping exhaust manifold and escaping exhaust fumes/noise are in your future.
Marshall

Re: Exhaust manifold sag
 

Re: Exhaust manifold sag
 

A new manifold with all the fixin's are on order

Re: Exhaust manifold sag
 

I'm going to need to see proof of this claim. I don't think it's true and I don't think there's any evidence to support it. If the gland ring decision was reversed because the manifolds were warping, why put them into all four exhaust ports? Wouldn't one ring in #4 have sufficed?

Furthermore I don't think there's any evidence that having or not having gland rings has any effect on warped exhaust manifolds. The warping is adequately explained by the factors described in Vince's article – heat cycling and a design that puts the strain on the manifold outside the area supported by the studs.

It's much more likely that the gland rings were put back in to do what they are designed for: protecting the manifold gasket from superheated exhaust.

Re: Exhaust manifold sag
 

Cast iron grows when heated to a moderately high temperature. You can see this if you look at the grates in old wood burning cook stoves. The design of the exhaust manifold is not symmetric so it warps as it grows. The gland rings will help but they should be placed on all four cylinders to keep things in alignment. A cast iron manifold can be straightened by putting stress on the manifold when it is heated to a high temperature, but this is tricky and about half the manifolds crack. This is done in the Model T world but I have never seen it talked about in the Model A world.

Re: Exhaust manifold sag
 

I keep thinking someone will come up with a procedure to take the sag out. I have a collection of some 10 sagged units. In one of the early books on restoriaton there is a diagram to take sag out.

Re: Exhaust manifold sag
 

I have had three Model As in the last 10 years and have had to replace the exhaust manifolds on all three. Fortunately the reproduction manifolds appear to be of high quality. Don’t forget to have your intake manifold decked to your new exhaust manifold so the mounting surfaces are coplanar. I find that a gray ceramic exhaust paint like Cast Blast (available from Snyders, but there are others) helps keep the new manifolds looking fresh.

Re: Exhaust manifold sag
 

You could install it upside down, put on a downdraft carb, reroute the exhaust, and drive it for 50 or so years…..

Re: Exhaust manifold sag
 

I have found many gland rings inside mufflers. Just sayin'.

Re: Exhaust manifold sag
 

The gland rings have a gap in them, so they are not capable of supporting anything. Those rings prevent burnout of the copper gaskets. Ford added a rib to the exhaust manifold in an attempt to keep it from failing / sagging. In my opinion, the exhaust would benefit from an additional support in front of the muffler. However, the support would have to allow motion of the exhaust pipe just as the existing support clamp does.

Re: Exhaust manifold sag
 

Trying to circle back to Russell's original question, it's notable that the earliest Model As (prototypes and the first 200 cars that were never meant for sale to the public) used an exhaust hanger which was a band that went around the middle of the baffles, rather than down at the end of the tailpipe. This arrangement would have allowed the hanger to take essentially all the weight of the tailpipe and might have prevented the future problems with the exhaust manifold.

It's pure speculation on my part, but I wonder if what happened was that the early hanger bracket setup tended to fail due to thermal contraction and expansion of the tailpipe, so the bracket was moved to the end of the pipe, but at that point it was too late to radically redesign the manifold.

Re: Exhaust manifold sag
 

When I was a kid growing up on the farm, we would have to go out and check the irrigation system at least once during the night to make sure that it was operating as we hoped it would. The pump engine's exhaust manifolds would glow with a dark red color all night. Most of the time a person doesn't think about that when driving a car during the hot times of the year but that old manifold takes a beating from the heat. The weight of the exhaust system certainly doesn't help but it takes quite a few long miles to get them to sag. If they could talk, they would be screaming for mercy and be telling us traumatic tales of woe.

Re: Exhaust manifold sag
 

If the old manifold leaks then it goes to scrap. I love the fit and look of a new manifold and they are not high dollar.
Now the old heater manifolds, I've never had one leak.
Do the B exhaust manifolds sag?

Re: Exhaust manifold sag
 

Stress on the exhaust manifold when heated will contribute to warping, but most of the warping is due to the cast iron growing when heated.

Old model airplane engines had cast iron pistons and no rings. One trick to restore compression in a worn engine was to heat the pistons so that they expanded a bit and would fit tighter in the cylinders when cooled back down to room temperature.