440 through manifolds, 2.5" or 3.0" exhaust?

[1 Wild R/T]

Just in the planning stage right now, putting together my 68 Coronet R/T vert.... I have parts I could use but not sure it's the right choice...
15 years ago I bought a full 3.0" TTI system including 2.0" tube headers and the tips from a man who overextended himself..

I also have 2.5" tips and 2.5" ultraflow mufflers should I decide to go that direction... I'd collected that prior to scoring the TTI stuff...

The car isn't gonna be much of a hotrod, well... It'll be a 440, 240 @ .050 cam, ported 915's, light pistons... Good parts, but it's a vert, it won't see track time... It'll be running a 727, 3.23 gears and a 29" tire...

I fully intend to run manifolds, I could buy TTI 3.0" head pipes & run the 3.0" system.... Or I could do a 2.5" system which I think is probably a better match for the car.. Kinda concerned about the ground clearance and clearance with 3" exhaust around the torsion bars & axle....

Anybody care to tell me which way I should go & why?

 

[Kern Dog]

Years ago, Andy Finkbeiner wrote an article on this.
He did some testing with a big block, it may have been a 440....with the .528 solid Mopar Performance cam, HiPo manifolds and 3" head pipes.
It was an impressive article. Most would expect a high performance 440 to be fitted with headers but some camshafts seem to still do quite well with cast iron exhaust manifolds.
I can see the appeal of manifolds. Ground clearance is never an issue, gasket issues are next to non existent and if the cam is mild enough, you may not notice that much of a power loss compared to headers.

 

[R413]

I had a 67 with manifolds and 3" TTI pipes out the back. Fit decent under the floor, looked like sewer pipes under the tail end. Hung down and looked like a teenagers car.

 

[1 Wild R/T]

I had a 67 with manifolds and 3" TTI pipes out the back. Fit decent under the floor, looked like sewer pipes under the tail end. Hung down and looked like a teenagers car.

Not planning to have this look like a teenagers car... But if the pipes tuck in reasonably well I think they would sound good & I'm sure it'll run well enough to keep me happy...

 

[Kern Dog]

I was told that by the time the exhaust gets to the tailpipes, it has reduced in temperature to the point where going one size smaller in pipe diameter (Than the head pipes) had no effect on power.
I have not tested this but I do have a 3" X pipe on the red car with 2 1/2" tailpipes and the car runs damned strong.

 

[1 Wild R/T]

Years ago, Andy Finkbeiner wrote an article on this.
He did some testing with a big block, it may have been a 440....with the .528 solid Mopar Performance cam, HiPo manifolds and 3" head pipes.
It was an impressive article. Most would expect a high performance 440 to be fitted with headers but some camshafts seem to still do quite well with cast iron exhaust manifolds.
I can see the appeal of manifolds. Ground clearance is never an issue, gasket issues are next to non existent and if the cam is mild enough, you may not notice that much of a power loss compared to headers.

My cam is a Bullet SFT chosen to work well with manifolds, If the system I picked up had the smaller headers I'd probably run them but these are the 2" tubes, so less room under hood, more high RPM oriented... When I picked them up I was putting together a 69 RR with a 512 cause there were plans for a racetrack 30 miles from here... Obviously that got scrapped, this is Commiefornia after all... So the big tube headers will find a new home....

I'm not worried about extracting every last horsepower, just using the parts I have to achieve a good result... But I have enough of the 2.5 system that I'm not opposed to going that direction either.

 

[Kern Dog]

I sure like the theme of using what I have to keep costs down.

 

[1 Wild R/T]

I sure like the theme of using what I have to keep costs down.

Well, I'm certain I'm not gonna use the headers... But I do have six sets of HP manifolds so that's easy.... I would need the 3.0" head pipes which I'm thinking I would order ahead of time & pick them up at Spring Fling....

 

[Kern Dog]

Shoot, man.....A couple sets of those manifolds may pay for those headpipes.
I am always looking to sell something here to pay for something that I want to do.

 

[JooCis]

Just in the planning stage right now, putting together my 68 Coronet R/T vert.... I have parts I could use but not sure it's the right choice...
15 years ago I bought a full 3.0" TTI system including 2.0" tube headers and the tips from a man who overextended himself..

I also have 2.5" tips and 2.5" ultraflow mufflers should I decide to go that direction... I'd collected that prior to scoring the TTI stuff...

The car isn't gonna be much of a hotrod, well... It'll be a 440, 240 @ .050 cam, ported 915's, light pistons... Good parts, but it's a vert, it won't see track time... It'll be running a 727, 3.23 gears and a 29" tire...

I fully intend to run manifolds, I could buy TTI 3.0" head pipes & run the 3.0" system.... Or I could do a 2.5" system which I think is probably a better match for the car.. Kinda concerned about the ground clearance and clearance with 3" exhaust around the torsion bars & axle....

Anybody care to tell me which way I should go & why?

Personally, I’d lean towards the 2.5 setup. With manifolds and intended for cruising, the 3 might be overkill and cause clearance headaches you don't really need

 

[451Mopar]

I used the 2.5" TTI X-Pipe exhaust on my convertible. Need to watch the tail pipe fitment around the fuel tank.
I tried making the car a bit quieter with Walker Quiet-flo mufflers, but they don't seem much quieter (at idle) than the Super Turbo mufflers that came with the TTI kit.
I found that the 2.5" Quiet-Flow mufflers do neck down to 2-1/4" inside the muffler anyhow, so I likely would have been better off staying with the super turbo mufflers.

 

[Runcharger]

2.5 I think. I like the 3 inch for 5000RPM and up 500+ inchers. Thats what has worked for me anyway.

 

[eldubb440]

you know the answer........

 

[496 polara]

2.5 system with the Ultraflow mufflers would be my choice. I get the simplicity of manifolds but I would be hard pressed to not run some 1 3/4 headers (cause 3.23 gears).

 

[Hilljack68]

I forget the source, but I had read an article some time ago, indicating exhaust sizing is mostly dependent upon displacement and HP. I made a spread sheet at the time. I'm no rocket surgeon, but for what it's worth...

 

[lewtot184]

Manifolds are 2 3/8" i.d. i'd do 2 1/2" pipes. Manifolds don't like a bunch of valve overlap. You might be surprised at how well a lesser cam will perform with manifolds.

 

[493 Mike]

I believe the 2 1/2" system will provide better scavenging, especially with manifolds, and better clearances of course. Since it is not a maximum effort build, go for maximum throttle response.
Mike

 

[furious70]

Engine masters did tests on this sort of thing.

If buying from scratch - 2.5"
If you can sell the 3" stuff, 2.5.
IF not, use what you have

 

[dfrazz]

This was a good test -

 

[WileE]

For that engine, and using stock exh manifolds... 2 1/2. Sell the complete header/3" system.