Cross-over pipe on duals

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.