Max pipe diameter for a 318?

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MoparFan

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Hi,
does anyone knows what is the maximum diameter of exhaust pipe that can be attach to the stock manifold of a 1972 318? (just in case the muffler shop guy want to take the easy way with a small pipe!!!)

I would like to run the whole system in 2.25 or 2.5"...

Thanks
 
Leaving it as is. 2 1/4. Plans for mods in the future? 2 1/2. I actually run 3" on my 318, overkill for now, but will be just right when i drop my 360 in :D
 
ok ... I think I will go with the 2.5" for the future. But, do you know what maximum size of pipe the flange manifold can accept on these engine?
 
The manifolds on my '85 pickup and '88 van with a 360 would only take a 2.25" pipe so your manifolds are probably the same or they may only take 2". If that is the case I would do a step system form the 2" to 2.25" pipe. Exhaust is just like a camshaft and bigger is not always better and can be worse. The exhaust system in a normally aspirated engine (non-forced inducted) helps scavange the cylinders. If you go to big you can very easily loose torque and horsepower.
 
I am happy with my setup.

I am using, step up from stock 1 7/8" (1964 Abody manifold)
up to 2 1/4" thru Dynomax Super Turbo mufflers.

Edelbrock 600 cfm, # 1406 carb
Edlebrock LD4B intake.

Mopar Performance cam, .435/ .450 lift part #4452759

Basic Operating RPM Range: 1,200-5,200 RPM
Intake Duration at 050 inch Lift: 221
Exhaust Duration at 050 inch Lift: 228
Duration at 050 inch Lift: 221 int./228 exh.
Advertised Intake Duration: 260
Advertised Exhaust Duration: 268
Advertised Duration: 260 int./268 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.430 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.450 in.
Valve Lift with Factory Rocker Arm Ratio: 0.430 int./0.450 exh. lift
Lobe Separation (degrees): 110

I also have # 302 casting heads. :)
 
an experienced guy at the mufflershop can easily decrease a 2½" pipe to whatever pipesize that fits your manifolds before puting a flange onto the pipe and then flare it out to fit the manifold or gasket, but that will just bee 2" inches of thin pipe
 
Hey Caveman, have you ever ran your car down the drag strip? How does it perform? Toolmanmike
 
toolmanmike said:
Hey Caveman, have you ever ran your car down the drag strip? How does it perform? Toolmanmike
Click to expand...

Not yet, stock 2.93 sure grip,
it moves pretty good though. ;)

Took the car to Bennington VT tonight for the
Hemmings Cruise, a 1968 Dart 340 beat me for best Mopar of the night.

I would say he won it over my car, by a lot.

LOL< he runs FAST with a 400+ cid, small block,
that looks like a 340. :headbang:

He said he has a best of mid 12's. 8)
 
2" OD pipe flared to fit the 1-7/8 manifolds is what is used for the flange pipes on a 318. After about 18-24" and near the bell housing , a larger intermediate pipe can be made to continue downstream to the muffler. Anything above 2.25" would be pointless
and ineffective. Larger than 2.25" can cause more interior resonation , loss of low and mid range torque.
 
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