Noisy Exhuast

T

tefergy

Junior Member
Hi everyone. I have recently completed restoration on a '28 roadster and the motor has seemed particularly noisy to me. I found a bit of a problem with the exhaust gasket (see attached) which I have since replaced with a copper clad gasket. This has helped the noise immensely, however it still seems like 1 cylinder is louder upon combustion then the others - much more noticeable under load, at idle it runs beautiful.

The question I now have is, I have a modern Lukey muffler on it rather then the repo tapered muffler. Is it likely that the modern muffler creates too much back pressure, and not allowing it breath quietly??

Many thanks.
 

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Here is the final product at its first rally - noisy exhaust and all
 

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it could be you have a high preformance muffler (for built up engines) or your valves may not be properly set.
John
 
Sounds like you have a leak at the rear exhaust port ; very common.
Use best quality manifold gasket plus exhaust gasket cement. The cement will make up for any slight warping in the manifold, even if it has been planned, or maybe you have a new one.
If you have not got one, get a good recent Model A Manual, eg. Les Pearson or L. Andrews. Good luck.
 
Have you tried to retighten the manifold nuts? Not too tight, but just use common sense. Did you put a straight edge on the manifold? The rear is the one that sags and gets out of alignment, and if it's bad enough, it's best to buy a new exhaust manifold.
 
Is the manifold straight with no pitting giving a good seal?

Are there any others from Australia using the same muffle that can chine in?
 
Take a 2 or 3 ft length of garden hose and put one end to your good ear and use the other end around the exhaust manifold to locate the leak if there is one. Another way is have your wife hold a rag over the tailpipe while the motor is running and if there is a leak at the manifold you will find it.
 
whatever muffler you have it should still seal at the exhaust mainfold connections. if it was creating that much backpressure you would have a real lack of power. you can also try the smoke test by inducing very small amounts of ATF into the wiper vacuum port or through the carb intake to see if it smokes from under the hood indicating a leak. do not do this test inside :D
 
tefergy said:
Hi everyone. I have recently completed restoration on a '28 roadster and the motor has seemed particularly noisy to me. I found a bit of a problem with the exhaust gasket (see attached) which I have since replaced with a copper clad gasket. This has helped the noise immensely, however it still seems like 1 cylinder is louder upon combustion then the others - much more noticeable under load, at idle it runs beautiful.

The question I now have is, I have a modern Lukey muffler on it rather then the repo tapered muffler. Is it likely that the modern muffler creates too much back pressure, and not allowing it breath quietly??

Many thanks.
Click to expand...


You have a problem with the rear exhaust port. Best to use the copper gasket. That green gasket is not the best. But you probable have a warped exhaust manifold.
Check with a straight edge. It should be flat on the face of the ports. Also make sure number 4 port on the exhaust manifold is not sagging lower than the rest.
 
Also, ensure that #1 spark plug has its metal gasket ring in place and that the plug is tightened securely. Exhaust leaking past the spark plug threads will make that cylinder seems loud. A simple check.
Marshall
 
Hi all thanks for your responses. Below is a couple of pictures of the muffler, as you can see nothing like original, however it was purchased 20 + years ago when I originally mechanically rebuilt the car. I have only recently completed the body work and got the car complete as a whole.

The motor has also been stripped and rebuilt in the last year. I have checked compression and valve clearances - that is all fine. I have checked and rechecked timing. I am fairly confident that the manifold is ok, it has been surfaced & I put a straight edge on it and all looks good. I now have copper gaskets & it is tightened to 45 pound with the motor hot. I don't have gland rings on each of the ports, though I do have the recess in both the block and the manifold, so I could try them (I need to buy some gaskets from Snyder anyway, so could get a set of them also). And finally yes new spark plugs and washers on all 4.

So basically I am toying with the idea of buying a repo original style muffler, but its a lot of money to shell out to simply see if it will fix the issue??

Thanks for your interest and suggestions.
 

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