What is the best or minimun size to make the exhaust pipes for my 56 f100, using a 351w with headers and edlebrock intake with a 600 cfm carb? Also is a cross over pipe or H pipe a good idea and why? Thanks

 

Is your 351 stock? If not what kind of goodies you got? Primary tube size as well as secondary size affect engine perfomance. In the spirit of getting the most out of what you got, you want everything pulling together.Low end performance smaller primaries, high winding high end larger primaries.Are you running a full length exhaust? All these affect perfomance?

 

My 56 has a 351C with the same intake and carburator. It also has a mild cam.
My headers are 1 5/8 dia primaries to 2 1/2 dia collectors, cross-over tube, flowmasters to dual side dump exhaust.
Great low end grunt and revving to 4500. Power and torque start to flatten about there (from dyno run).
I understand that the cross-over tube helps balance the two sides together.
I really like the setup. The truck came basically that way, though, so I don't have any other setup to compare it to.

 

This engine has a mild cam and the headers have not been purchased yet. But I probably will not have a big choice since clearance issues will affect the choice. I would like to run the exhaust out the back but have installed a new tank under the bed and again clearance issues may force me to run it out in front of the rear wheels.Also please define primary vs secondary pipes. Thanks for your input.

 

Not that I think I'm an expert on headers and exhaust geometry, but here's what I think I know:
The tubes on my headers are all full length from the head to the collector. The term "secondary" tubes applies to a Y-style header where the primary tubes (from the head) join two-into-one (the secondary tube) before the two secondaries join at the collector. Tube diameters increase from primary to secondary to collector to allow for the increased gas volume. These style headers are better at scavenging gases from the cylinders and generally perform better at high rpms, but need more efficient intake manifolds (like a dual-plane high-rise) to balance the performance on both sides of the cylinder.
Small diameter tubes/ports have high gas velocity and perform well at lower rpms, but the power will flatten out sooner because the gas can't move out of the way fast enough at high rpms.
Large tubes/ports are "lazy" at low rpms. but provide less backpressure and improved performance at high rpms.
Running the exhaust out the back will be a lot more quiet. A good muffler guy can easily get the tubes around the rear gas tank. I really like my side dumps and the bigger sound they make, but I'm a rodder guy.
If you run a stock-style muffler, or if you join two exhaust tubes into one exit tube, you will negate most of the gain available from the headers, due to higher back pressure. Plan on using flowmasters, Magnaflow, Thrush or other perfomance mufflers. They will still be quieter when you exit out the back.

 

Learpilot,

My '59 has a 302 with Edelbrock Performer manifold, Carter 625cfm carb, Ford Racing aluminum heads, CompCam 268, full roller rockers, 1.7 rods and ceramic block-hugger headers. The exhaust is a 2.25" aluminized dual exhaust with Series 40 mufflers. The exhaust tips shoot out one on each side in front of the rear tires (for the same reason yours might have to: the fuel cell behind the rear end melon).

2.25" seems to work fine for me. At the same token, a 2.5" would have worked equally as well. Six of one, half-dozen of another. I opted for the 2.25" for a bit more back-pressure that's all.

Don't know how much this info will help, but it may give you more to compare against and help in your decision making.

Best,
Daryl
(aka, Butch n Me)

 

Learpilot

I also have a 56 F100 with a 351W/AOD. Engine has same carb and intake as you, I also have the performer cam. At the moment I have the stock exhaust manifolds with the pipes upsized to 2 1/2 with a crossover just behind the trans. The mufflers are flowmaster 3 chamber. The exhaust tips exit at the rear under each fender (same idea as a early GT Mustang (I know they didn't have separate rear fenders)).

After I had the exhaust system made by a so called exhaust expert (not a very good job) I removed the tank from inside and installed a aluminum one at the rear. I made about 20 cuts on each pipe to get them to remain exiting at the same place but give 6 inches clearance to the fuel tank. I had also changed the transmission from a FMX to a AOD so I had a new drive shaft made and without thinking to much on the subject I let them talk me into a 1 inch larger O.D. on the shaft so now the mufflers are sort of close to the driveshaft and now I am thinking about changing to Mustang headers (not sure if they will clear the Volare steering gear)

The rear suspension has been moved up approx. 1 inch and I have reversed eye springs and the shocks have been moved out 2 inches per side (to help exhaust go over axle) right pipe needs to be rerouted over axle.

When I have the new exhaust system made I hope to use Mustang short headers 2 1/2 inch pipe with a crossover and the new slim line flowmaster mufflers also the tips will exit at the same place they do now.

I guess the moral to this story is try to have your ideal package and find a better exhaust guy then I did. By the way the crossover helps balance the exhaust flow and seems to quiet the system a little but I think the new mufflers will make up for that.

If you want to see the routing around the fuel tank there is a picture in my gallerie.

Chuck

 

Hi Learpilot,
I recieved your e-mail, but could not reply because it seems you have your e-mail turned off.

To answer your question.........
https://www.ford-trucks.com/forums/s...d.php?t=295218

Sorry, I didn't mean to hijack this thread but it was the only way I could get back to you.

And now, back to our regularly scheduled program.......

 

I'm also using a 351w/Toploader and a Volare clip. 2.5" duals, with a crossover ready to be installed. I'm using BBK Mustang headers because they were already ceramic coated.

The mustang headers will "probably" work without much problem if your motor is offset at least 1". If not, you may need to add a third steering joint to get around the header. Interference with the streering box will not be a problem, the problem is with the steering linkage and the header.

Mike
'55 F-100

 

Another vote for 2 1/2 for your combo. H pipes are supposed to equalize exhaust pulses, and smooth out flow. They are a good thing. They are also a pain in the **** if you have to have to remove transmission later so I usually skip it. If you run one, keep it away from the tranny pan.

 

Kenny , thanks for the info,sorry to bother

 

Learpilot - Sorry I completely missed answering your question and got off into header sizes and styles.
My 56 uses 2.25 dia exhaust tubing.

 

thanks for all the great info, when I figure out how to post pictures I'll show you guys what I working on.