Thread: Exhaust Diameter Recommendations

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Have installed a stock 5.0 Ford small block with AOD in a 32 roadster project. Engine is currently stock, motor came from a Crown Vic. I am converting the EFI to a carb, motor has headers. I will be fabricating the exhaust shortly, what diameter exhaust tubing should I go with?
Thannks

I like to use tubing 1/4 inch bigger than exhaust valve and go as straight as I can wherever I can( not lots of tight turns and twists close to the head) this will usually give you an pipe ID about 1/8 inch bigger than the exhaust valve.

I also make an effort to pair the cylinders in 2 different lenghts to broaden the power curve and join the collector in the firing order rotation

Use a merge collector and tapered connectors where you can

id say 2 inch or 2.5

Most of the long tube headers for small Fords run 1 5/8". You can get 1 3/4 but I haven't seen them any bigger. That doesn't mean they aren't out there.
There are a lot of choices for short tube headers and block huggers and they can be found pretty inexpensive on ebay.
Personally, on a stock 302 for street use I would stay with the smaller tubing for headers and the 2 or 2.5 for the rest of the system as mentioned.
Jerry, I like your formula. I never heard that before.

on a relatively stock 302 a 2 1/4" exhaust system using 1 5/8" headers is usually the best size to use for a street car is what I was told by the guy that built the exhaust system for my Cobra roadster. Since my engine was a built, hi-reving, 7200rpm, 385hp 302, he built 1 3/4" tuned headers into a 3 1/2" collector, then into 3 1/2" muffler/side pipes, .

Somewhere on the net I found a couple of articles on exhaust/pipe dimensions for my mildly modified 5.0 Ford crate motor and ended up with Sanderson FF1 headers and 2.250 pipes. I haven't run the car yet, so really don't have performance figures yet, but have to "assume" that it will be fine for my general everyday driving as for sure, it's a whole heck of a lot bigger area wise then an Explorer or Crown Vic. For a race and most of the time full throttle operation, would have gone to 2.5 or 3 inch.

The only drawback to 2.25 - some parts are not always available

This mainly a progress report to IC2. It may fit in here right after the picture of his neat chassis layout showing his exhaust system. I am stumbling forward in my buildup and learning what I don't know at every turn so I just copied IC2's recommendation and went to a local muffler shop (Economy Mufflers at the Hanover Air Park) and had a system installed with turbo muflers and 2.25" tubing with an H crossover. With a chance to get underneath I also saw some aspects of my chassis that are very low and I may change some of that. As IC2 said, the muffler shop politely declined to use the pipes that I purchased from Speedway and welded their own setup in a few hours. Although the shop is called the "Economy Muffler" shop it did not seem economical to me, but then I remember when a Pepsi was five cents and gas was $0.259/gal. so I am out of tune with todays's costs. The whole system was just under $600 but I also had to pay towing to and from the shop. Hopefully this is the last time I will have to use towing! Turbo mufflers are about half the price of performance mufflers so I saved there and the shop said the turbos would be quieter and that will lessen complaints from the wife and yet still provide pretty good flow. One good thing is that this shop has worked on a lot of performance cars so they knew just what I wanted and actually there is no way I could have maneuvered the pipes the way they did around the SBC oil filter and my master cylinder. Using their pipe bender they made spaghetti out of those pipes! Another problem is that I have large brackets for the rear bumper so they could not put the pipes over the axle even though I have set the coilovers on the highest setting so they bent the pipes under the axle but still within the clearance carved out by the four bar brackets under the frame. If the fourbars clear the pipes will too, if not the four bar brackets will bottom out first. This was a major step forward for me and now I can spend time on the wiring. Thanks again for much help from folks on this Forum!

Don Shillady
Retired Scientist/teen rodder

Originally Posted by Don Shillady

This mainly a progress report to IC2. It may fit in here right after the picture of his neat chassis layout showing his exhaust system. I am stumbling forward in my buildup and learning what I don't know at every turn so I just copied IC2's recommendation and went to a local muffler shop (Economy Mufflers at the Hanover Air Park) and had a system installed with turbo muflers and 2.25" tubing with an H crossover. With a chance to get underneath I also saw some aspects of my chassis that are very low and I may change some of that. As IC2 said, the muffler shop politely declined to use the pipes that I purchased from Speedway and welded their own setup in a few hours. Although the shop is called the "Economy Muffler" shop it did not seem economical to me, but then I remember when a Pepsi was five cents and gas was $0.259/gal. so I am out of tune with todays's costs. The whole system was just under $600 but I also had to pay towing to and from the shop. Hopefully this is the last time I will have to use towing! Turbo mufflers are about half the price of performance mufflers so I saved there and the shop said the turbos would be quieter and that will lessen complaints from the wife and yet still provide pretty good flow. One good thing is that this shop has worked on a lot of performance cars so they knew just what I wanted and actually there is no way I could have maneuvered the pipes the way they did around the SBC oil filter and my master cylinder. Using their pipe bender they made spaghetti out of those pipes! Another problem is that I have large brackets for the rear bumper so they could not put the pipes over the axle even though I have set the coilovers on the highest setting so they bent the pipes under the axle but still within the clearance carved out by the four bar brackets under the frame. If the fourbars clear the pipes will too, if not the four bar brackets will bottom out first. This was a major step forward for me and now I can spend time on the wiring. Thanks again for much help from folks on this Forum!

Don Shillady
Retired Scientist/teen rodder

Don,
From what I can see it appears to be a very nice looking system. As far as $600 - probably about right with the current price of steel. My +/-$30 ten foot length of tubing is about doubled in price. The mandrel bent U and J bends I used have gone up a couple of dollars each. My $85 each Flowmaster mufflers are now ~$100. Then the cost of labor. And yes, I do recall gasoline at 5 gallons for a buck, then getting upset when Coke went to .06 (gasp!!) then looking at the bottom to see where the bottle really originated

Originally Posted by IC2

Don,
And yes, I do recall gasoline at 5 gallons for a buck, then getting upset when Coke went to .06 (gasp!!) then looking at the bottom to see where the bottle really originated

Talk about showing your age!!!!!!!!!!!!!!!!!!!!!!!!!! Though I do remember as a high school kid when $.50 would get you a Coke, bag of peanuts, and a pack of smokes!!!!!

How much was beer back then? You guys only mention coke for a nickel.


Hot rod mag did a story in the last couple of months about this subject, they tested all different size pipes on the same car and if i recall right , the horsepower/ rpm range went up with the larger pipe diameter Ie with 1.75 was 300 horse at around 3500 rpm, but with 2.50 pipe it was 425 horse at around 5000 rpm. It was pretty consistant with the highest horse peaking at lower rpm with the smaller pipe, then gaining both with larger pipe diameter.Ill try to find the issue.

Originally Posted by hotroddaddy

How much was beer back then? You guys only mention coke for a nickel.

A case of Budwater was less then $4.00 and Cooraid was a regional drink and only popularized by Smoky and The Bandit movies in the '70s

Since I haven't read a Hot Rod Magazine in years, for sure would have missed that article - plus in the last few years their credibility IMO seems to have slipped. I wish that I could find the formula that I used for mine - but it did come up with the 2.25 diameter

I had my local muffler shop bend 2 90 degree front pipes based on 2 crappy pipes and a cardboard sketch and measurements of what I wanted changed. He charged me $50.00 (the lowest charge he does) for what could have been a "No, we do not do custom work without the car" refusal. I haven't tried the pipes yet but he did do exactly as requested + throw in a couple of cast iron manifold flanges I could not find anywhere. If these pipes do not work, its my fault not his.

When my dad was young and lived in oregon he and his buddies would drive down to north cali just to get coors, cause they did not sell it there yet. that was way before smoky

Originally Posted by hotroddaddy

How much was beer back then? You guys only mention coke for a nickel..

Here in Colorado in the long ago times a sixer of Coors was $.98 +.02tax. For five bucks you could put gas in your car, get a sixer, take your date to the drive-in, get a couple of burgers and fries at the stand...and if you were real lucky..."get lucky" lol

Originally Posted by hotroddaddy

When my dad was young and lived in oregon he and his buddies would drive down to north cali just to get coors, cause they did not sell it there yet. that was way before smoky

Coors before Smokey wasn't sold East of the Mississippi - probably had some verbal agreement with Budwater or Miller or Piels or Yeungling. I thought it was a big deal and the regular stuff is even OK - then they started pushing that light near beer........