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Old 09-20-2011, 07:32 AM   #1
JerseyJim
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Default 40 Ford Stock Exhaust Size???

My 40 Ford Sedan Delivery has a 41 engine rebuilt to 100 HP. The single exhaust pipe by today's standards looks ridiculously small. Checked it today and it measures 1.5 inches O.D. I'm wondering whether this restricted exhaust doesn't contribute to over-heating? Not that I would expect miracles... But just increasing this to 1.75" would result in 35% better flow even if you discount the reduction in back pressure.

I know that you more experienced flathead guys already have the answers to this and I sure would appreciate the help.
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Old 09-21-2011, 04:10 PM   #2
Ken/Alabama
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Default Re: 40 Ford Stock Exhaust Size???

My original 40 tail pipe measures 1.50 .
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Old 09-21-2011, 04:30 PM   #3
Don
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Default Re: 40 Ford Stock Exhaust Size???

I have duel exhaust.. coming off headers is 1.75 intro 2 in muffler ,out of muffler with 2 in pipe, expand it a little to go over outlet of muffler, has to make all the brackets to get a good seal .
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Old 09-21-2011, 09:56 PM   #4
Barlea
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Default Re: 40 Ford Stock Exhaust Size???

Some say 1 3/4" tailpipes make the best music of all. ..B.
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Old 09-22-2011, 05:12 PM   #5
JerseyJim
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Default Re: 40 Ford Stock Exhaust Size???

Thanks for the responses. I assume if I go larger, we're not talking stock and I'd have to have them made up?
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Old 09-22-2011, 07:59 PM   #6
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Default Re: 40 Ford Stock Exhaust Size???

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My Dad's 40 sedan has a stock 221 1940 Ford motor bored out to 239. It is connected to the stock exhaust system including the pea shooter tail pipe. The car has plenty of power and does not run hot (unless you are in a parade on a 90+ degree day). Ford realized the exhaust gases cooled down a lot by the time they exited the muffler. When gases cool they shrink. The smaller diameter tail pipe doesn't seem to choke off Dad's car at all. If you have a decent exhaust system I would leave it alone. If you need to replace the muffler and tail pipe I'd install whichever is easier.
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Old 09-23-2011, 09:42 AM   #7
JerseyJim
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Default Re: 40 Ford Stock Exhaust Size???

Thanks for the responses. Considering that Ford used a 1.75" exhaust system just a decade later on smaller displacement engines... Just speculating that a reduction in exhaust back pressure might be helpful. We all know that flatheads have a tendency to run hot. Some are better than others. Some are worse. I can drive mine without too many problems as long as I don't have to stop and start too much in hot weather. But who can predict when you may get caught in traffic. Any incremental improvement to me seems worth considering.
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