Leaking Exhaust Manifold

fordfun

fordfun

Member
I continue to work down the list of problems associated with the 1929 Sport Coupe I acquired 2 years ago, and I’m about to tackle a leaking exhaust manifold. As you’ll see in the attached photo, the system is equipped with an Auto-Lite heater unit. I have not removed the unit(s) from the engine yet as I’m attempting to extend the driving season a bit and I don’t have any replacement gaskets in hand yet.
I have a few questions:
1. If I find that the manifold is damaged (cracked, warped, etc.), can this type of damage be repaired or should the unit be replaced?
2. If replacement is required, is a “special” manifold required to accommodate the heater and if so are these available from the vendors?
3. I’d like to refinish the painted members. Would you recommend stripping, blasting, or some other method of preparation?
4. Are there any other obvious problems indicated in the attached photo?
5. The car tends to backfire when going downhill. I recall reading elsewhere here that this may be caused by a manifold leak. Does that make sense?
 

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1 if manifold is cracked yes it can be welded to
2 venders do not sell manifolds with the right type for your heater
3 I sand blasted mine it looks great
4 replace gas line with the proper line
5 yes that can cause it to back fire

Welcome to the Ford Barn
 
I had some leaks in my intake and exhaust ports and the carb base. I put in a new copper sandwich gasket, new studs and new nuts. When I had the manifolds off (with the intake still attached to the exhaust manifold) I took them to a machine shop and they planned the port surfaces and smoothed off the carb base. It cost me $25 to have it machined, which is a lot cheaper than spending a couple hundred bucks on new manifolds. I made one mistake. I thought I might as well make the manifolds look prettier so I sprayed them with some engine paint. It worked well on the intake, but the exhaust manifold gets too hot and it burned the paint right off. Drove around with some burning eyes for awhile. The new gaskets definitely helped with my backfire issues.
 
Thank you all for your guidance here. I'll be picking up the necessary materials next week to deal with the manifolds and replacement of the gas line.
 
FWIW: Life Safety First.

A. Copper Gas Line Experience:

Per response #5, had a copper gas line that with engine vibrations it fractured at the carb fitting & leaked. Installed new copper line with a 360 degree bend midway to allow for flexing -- used it for 55 years & it never fractured again.

B. Manifold Experience:

Have manifold heater similar to yours. Smelled just a slight bit of engine fumes in cab with heater installed in cold weather. Noticed the original ex. manifold had sagged & became slightly misaligned; but not cracked. With a heater like that, one small exhaust leak "anywhere", & carbon monoxide enters your cab through the manifold heater. Bought new matching Int./Ex. manifold & copper gaskets & did not take a chance of becoming asphyxiated or going to sleep at the wheel. Cheaper steel manifold gaskets rust out quickly & will soon leak in humid climates. Just me, but I think new manifolds are cheaper than undertaker services & minister services .............. plus you are guaranteed to continue to receive your Social Security check & working on your Model A.

Hope this helps thinking about your important Model A decisions.
 
The proper Model A gas line will not work with your carburetor which has the fuel inlet toward the radiator. Model A carburetors had the fuel inlet on the side. Maybe that is a Model B carburetor on your car, or maybe it is an aftermarket type, I cannot tell for sure from the photo.
 
The exhaust manifold also can droop down at the end near the firewall, which can make it hard to align properly with the exhaust port and cause a leak. Cracks can occur at the same place. I had this happen on my car. I replaced it with a used manifold that was still able to seal properly. I am sure there are others more knowledgeable that I who can provide more informed input.
 
I agree with H.L. in post # 7 about copper gas lines . I've never had a copper gas line break. I think this is mostly an old hear say that has been repeated so often that most actually believe it. A lot of the old model A guys probably remember the copper gas lines that use to be sold by Warshawsky and J.C. Whitney and never had a problem . In the 60s it was common to se a 360 degree loop in the center of the gas line. I never knew why, many said that any water or trash would collect in the low point of the loop. Now I see what H.L. is talking about. Now the vendors sell pre formed steel gas lines. The only gas line that ever cracked for me is a steel one that I formed for my dual updraft carb setup. If it ever cracks again it will be replaced with copper. Copper is much easier to bend and form. Usually the waffle style heater manifolds don't sag as badly as original exhaust manifolds because of the extra strength that the upper waffle adds. Over tightening is probably the main cause of warping exhaust manifolds. The outer ends of the model A exhaust manifold has no studs and nuts to secure it . The four manifold studs are on both sides of the intake manifold and only secure the inner edges of the exhaust manifold. When the nuts that secure the inner edges of the exhaust manifold are over tightened it puts a twist on the ends of the manifold and this is how the exhaust manifold gets warped. I lay a metal straight edge across the manifold to check for warpage. If there is an automotive machine shop in your area, sometimes the manifold assembly can be milled. It is best in many cases to just buy a new ceramic coated manifold from Snyders. I only use the two piece late 1931 copper clad manifold gaskets. These gaskets are wider in the ports, cover more area and give a better chance for a good seal, especially if you are using an old original manifold with a bit of sag. The one piece steel gaskets are only clad on one sise and really don't last as long, I've tried them !!! Cracked manifolds can be brazed in some cases. We recently had a thread about welding cast iron and the success rate isn't very good, especially because of the carbon deposits in the exhaust manifold. As for painting the cast manifolds, sand blasting would do the best job for paint prep. I have throughly wire brushed manifolds and had good results painting them with Cast Blast paint from Snyders . Cast Blast looks just like new cast iron and is still holding up good on my roadster after eight years. Exhaust manifold gasket leaks cause pops when decellerating and can contribute to loud backfires a few seconds after the engine is shut off. For tighten the manifolds when installing, I just use a 3/8 ratchet and a deep 11/16 socket. Just tighten from the inside out using common sense to avoid over tightening and warping. Check and retighten after heat cycles untill the manifolds finally settle down.
 
I had a good laugh about the copper fuel line, here's a photo of mine in 1972. Even though it was large tubing, and large compression fittings, I never had any problems with it leaking for many years of driving. That '31 carb has been great too, so I've never changed it.
 
YEs i have and there is a thread on it also.. I have used it 2x now and it works great.. make sure you tighten to at LEAST 25#, mine was at 30#. However i just also bought a NEW REPOP exhaust manifold and intake and they mate up GREAT together and went back to the copper gasket. Well made repo item for sure.
 
Thanks to all who added additional comments to the questions I asked. My next step will be to remove the manifolds and determine whether the exhaust manifold can be salvaged, as I understand that a replacement (which can accommodate the heater) may not be readily attainable. I'll keep you posted as I progress. - Bill

Forgot to mention that I'm running a "B" carb., which accounts for the fuel line entering the end rather than the side.
 
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