I had to laugh....

[R.White]

The exhaust on my car has been made completely in one piece!! Several sections welded together. Was this an original feature? I would be surprised if it was.

At first I thought I would not be able to remove the pipe without cutting it but with a bit of effort it came off.

The pipe itself has a certain amount of surface rust but is still serviceable but the muff'ler (silencer) is past it. I am hoping to find a suitable replacement but this time the system will be fitted in sections!!

Ray.

Edited May 12, 2013 by R.White
error (see edit history)

[Guest 1930]

I believe you will find a very clear picture of all the original section of your exhaust system in the MPB

[R.White]

Thanks for reminding me, Jason.

[Guest 1930]

No problem Ray

[R.White]

I checked out the MPB and like you say Jason, there is a clear picture of the exhaust components. The question, however, still remains; how was the original exhaust made? The photo (which I can't seem to copy and paste for some reason?) shows one section fitted to another but there are no clamps visible. Maybe the whole exhaust was assembled as one piece originally?

Do any original exhausts survive as patterns, please?

Ray.

[Pete K.]

Ray, My '25 has an old rusty system on it. (1950's?) Seems to still be OK though. It must have been replaced at one time or more, since new. It is put together in pieces with the clamps. The exhaust pipe has a clamp made to bind the pipe to the manifold. It looks quite strong, but I don't think it's original. I believe it originally had a large nut that threaded onto the manifold. I don't have a MPB. One of my top priorities is to remove muffler and clean it out, verifying I will have correct back pressure.

[R.White]

Hi Pete, my manifold, like many others I suspect, has also been altered to take a contemporary exhaust fitting; in my case a flange. This must have been a problem for people years ago when the Dodge type exhausts ceased to be available but quite how the muffler was attached is still unclear to me. From my point of view, it doesn't really matter too much.

What you might be able to help me with is this "back pressure" issue which is like something of a black art to me!! In other words, I am admitting that I have no idea how to check it or how much I should have.

I have found a local exhaust fitters who can make me a new system if required but I will see how my repairs hold up before rushing to line their pockets.

Cheers,

Ray.

[Pete K.]

Ray, In all naturally aspirated engines, correct back pressure is necessary to have engine run correctly. Think of it as a hydraulic fluid. The exhaust gasses have to go somewhere after leaving the cylinder. A muffler, or pipe system that is sooted up and partially blocked will have trouble exhausting the gasses and high fuel consumption will occur. It may also act as an EGR effect whereas exhaust gasses will stay in the cylinders, disrupting proper fuel/air mixture, resulting in poor running. I don't subscribe to this stunt, but back in the day, if one should have a vengeance against another, a raw potato forced up the tailpipe with a broomstick of the hapless individual's car, will prevent the engine from running at all for no less than a few seconds. That is almost 100% back pressure. The only ways to fix it is to remove the pipe and burn the now swollen vegetable out with a torch or replace the pipe. SO, if an old muffler has either a lot of carbon or a dead mouse, nests, etc... clean 'em out.

[R.White]

I can understand the importance of having the correct back pressure but my question is: how do I know what the right pressure is? How is it measured and can it be done by the likes of me in my garage?

Last year I had to replace the exhaust on my vintage Austin. Due to the difficulties I experienced in getting the bends up and over the axle right, I eventually settled for a simpler, less convoluted design. The system used the same muffler but slightly shortened. The result was nothing short of miraculous. A big increase in power and better fuel economy. I had to back off the throttle setting and even adjust the ignition a tad. The factory system may just have been inefficient. I have heared of "Tuning" an exhaust for racing but I know nothing of the process.

[Pete K.]

Ray, I'm not sure how to measure the back pressure and correlate that with factory spec's. on something 85 years old. Most all low-compression engine antique cars only require a "close to" tolerance back pressure by inspecting original literature, parts books, etc... to find what the original system would appear as. Some Model A Ford folks have discussed this topic in length on the "Fordbarn" website. My main objective when replacing an old system is to make one appear neat and clean using as much original looking pipes and muffler one can do. Safety is a prime concern among all of us, (I hope). The old "Flextube" piping has been illegal here for many years in an exhaust system. It's OK in an oil breather system though. I recall as a kid, I had a complete system made up myself for a '39 Plymouth using flextube pipe. This is a topic I will be keen to research soon, as my '25 will need a new muffler.

[R.White]

Thanks Pete, I expect there is some piece of garage equipment to measure back pressure in modern applications but I expect that for our needs a trial and error method will suffice. Your comment on safety is a salient one for me. Careful examination of the flange which has been fitted to my exhaust pipe in the past revealed that there was a small leak. I have just finished building up the area with weld and grinding down to provide a flat, sound surface for the gasket to seal onto. Back on the car tomorrow and off for a test drive... so long as the weather holds; we have had snow again today but it has come to nowt (as they say here in Derby).

Cheers,

Ray.

[Pete K.]

Did you say SNOW?!!!! Wow! Tomorrow, here in NEW ENGLAND is shorts and tee shirt weather. (finally). I'm wondering, Ray, do you think one of those modern type exhaust "doughnuts" would work OK with our Dodges? Getting the counter clerk to help would be nice since I don't know yet the actual size. I know the exhaust pipe is 2" dia. It would most likely take up some space between manifold and pipe that may not agree with the clamping device. I suppose longer bolts would be needed only.

[R.White]

Sure, Pete if your pipe and manifold joint fits together like that, then I would think a "doughnut" would do just fine (Pity I don't live near you - I could probably find one and bring it round!) but on my car and one other that I know of the manifold and pipe ends have been altered to the flat, triangle type flange with a three bolt fixing. It would be virtually impossible to find an original (6v/2 unit type) replacement manifold over here and I don't expect they are that easy to come by where you are - and then there is the question of not knowing exactly what that original screw clamp arrangement looked like and measured etc. If my car was all original or I was aiming at a 100 point concours restoration then perhaps it would be worth persuing but I just want to get as much done as I can; just in case we have nice weather and I can go out for a decent drive. (We did have some nice days recently, but it has gone back to winter again!! Brrrr.

Ray.

[MikeC5]

I did buy a reproduction muffler from Meyers or Romar and it appears to be period correct in as far as it is cylindrical and about the right diameter.

[R.White]

Hello Mike,

does your muffler have the pipes off - set? I have an unused "round" one which I plan on using but a straight forward swap is not possible because it's pipes are in - line. I would have hired a pipe bender but the ones on offer that I have found so far are not suitable for this size pipe in steel and my own pipe bender is also not up to the job. I have tried cutting, bending and welding pipes like this in the past but I have never been very happy with the job which always looks like a bodge. For the time being I have repaired my "oval" muffler but it is good to know you were able to get an authentic one from Romar.

Ray.