Cross-over pipe on duals

I just put manifold back duals on my stock 318-2bbl, 87 Ramcharger. They are 2-1/4" with turbo mufflers and no cats. Would I benefit any by putting a cross-over pipe in it before the mufflers? I have read that it helps produce low end torque and better milage. I think I lost some MPG by switching to the duals over the stock single exhaust, but I think partially because it still has the lean burn system ignition.
What do you think?

everything I have read about an H pipe or X pipe is positive - if you have the means - do it.. and let US know what YOU think! I do see that you have the H on your Dart.. does it work?

For the Dart, I have no before/after comparison. I did it all the same time and quite honestly I forgot about it until now. I have placed all my focus on making this truck a good daily driver. It shouldn't be too hard to fabricate a pipe between the pipes, before the mufflers and weld them together.

I put an X pipe on my car, but with a 408 and a 950cfm carb, it's got nothing to do with saving gas :twisted: again - would be interested in knowing if you do this and if it is effective.

Adding an H, or even better an X, pipe will result in a bump in torque. To be most effective an H should be close to the header collector which means working around the transmission. If you have the means do it but I wouldn't pay to have it done unless you include it as part of replacing the whole system.

An "H" pipe helps balance the exhaust pressures within the pipes. In return, this helps scavaging (sp) the cylinders of exhaust gasses. This leads to a cleaner intake charge producing more power with the same amount of fuel and air or a slight increase since there is now more room to breath in the intake charge due to less exhaust gas in the cylinder. The extra fuel is nominal but the return in power out weighs any loss with increased mileage gained from the fresher air and fuel charge. An "X" pipe does this a little better since it is stream lines by compare in even a rough layout or form.

Place the X or H at the rear of the trans for clearance & ease.

You should see increased mileage and power. However, you may to see much. The dyno would show you best. The gain is small but worth the expense. This is a mod I highly recommend to be done. It is one of a few modifications that help with power and mileage. A smoother running engine may very well result along with a serious look at the state of use on the engine and ignition.

LEANBURN

All leanburn computers should be discarded unless it is needed for that resto. At a min., the MoPar orange box should be installed. A MoPar Chrome box or FBO box perfurred!

Leanburn computers are known to just surprise drivers by suddenly cutting out. This problem was so bad, dealerships were stocking the old systems at high rates because they simply knew they would be used and sold. Leanburn computers were discontinued after a few years.

The one thing lacking on your carb after the leanburn conversion that you probably noticed while doing it is the lack of a vacuum advance port on the carb. The 4bbl. TQ can be modified by drilling a hole where the port normally goes and installing a proper sized fitting.
Or you can source out a after market carb or earlier TQ.

I do not know about the 2bbl. carbs ability to be modified for this conversion.

After the ignition conversion and carb modification (or new carb) is done in conjunction with the "X" or "H" pipe, there should be a well noted increase in power. Mileage should rise a little bit.

Example?

I had a '79 Dodge Magnum, 360/904/2.76 on 235/60/15's that went from a very best of 14 Hwy. with the leanburn, 2bbl. carb and single exhaust to a best of 20 (19 normal) Hwy. with dual exhaust off the manifolds @ 2-1/4 into twin high flow cats and Thrush Turbo mufflers exiting at the rear bumper. The Carter 625 emmisions AFB on top of the stock iron 4bbl. Intake was topped with a trap door air cleaner and K&N filter. Triggering the junk yard vacuum advance distributor was a basic MSD-6.

That leanburn was a terror and the carb was shot.

I will have to look and see if I can put the H pipe close to the manifolds. I do know that I can easily do it closer to the mufflers, with the way this exhaust system is routed.
Not sure how much it will help that far back, but I do see stock exhaust systems with a crossover before the muffs. What can it hurt? I don't think much.
I have a MP quick advance dizzy with the design2drive HEI module conversion on it, but just waiting for the new E-core coil to be delivered in the mail in order to install it. I don't see a way to add a vacuum port on the stock 2bbl, but I was still going to get rid of the leanburn and run as much mechanical advance that I can with the MP distributor, for now, until I find another carb or change to a 4bbl.

I prefer not to use one as it takes away from the exhaust note, IMO, while offering little to make up for the loss.

the factory installed h pipes on some models because they reduce noise.This allowed the use of less restrictive mufflers which would give a performance increase to some degree.Larry Sheppard,mopars head performance engineer says there is no gain with an H pipe.
I have no experience but it's hard to believe it would make power.

ir3333 said:

the factory installed h pipes on some models because they reduce noise.This allowed the use of less restrictive mufflers which would give a performance increase to some degree.Larry Sheppard,mopars head performance engineer says there is no gain with an H pipe.
I have no experience but it's hard to believe it would make power.

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Doug Thorley says the same thing.

No knowledge, but offer a few scraps. The first A-body 4 bbl V-8's used a single exhaust pipe that started before the tranny cross-over. They did have headers & collectors off the heads, as I recall. Apparently, the factory tested a full dual exhaust and found it performed worse, don't know if less max power or max torque.

When I owned a 1974 Honda 4 cyl motorcycle, the magazines were full of ads claiming 30% more power by installing their "4 into 1" exhausts. Finally, Honda and others started making the factory motorcycles that way and the same vendors seamlessy switched to advertising new individual exhaust pipes claiming "30% more power".

Perhaps H and X pipes are just eye candy, like rear disk brakes. Provide what people expect, though does seem like it would work. Next time a car rolls over in a NASCAR race, I'll try to notice if they use one. I am usually laughing at how completely non-stock they look underneath.