I put an H-pipe in my '68 chevelle back in the day, cost about $5.00 for the pipe and something like $20 to have someone put it in. That was back in my chevy days. Who knew that, even way back then, MOPAR engineers were putting them in their higher performance cars as OEM?

R.

If that 5th Avenue has the stock 2.21 or 2.45 gears in the rear axle, the engine is running quite slow even on the highway. With the engine running so slow, it shouldn't take a very large exhaust system to virtually eliminate back pressure at cruising speed. A large, freeflowing single exhaust (2 1/2 or 3 inch) may be nearly as good for mileage as a dual exhaust system in that particular application.

A vehicle with say 3.23 or 3.55 gears will force the engine to run considerably faster at highway speeds which means more exhaust will be produced. A dual exhaust would be more important for MPG with the numerically higher gears.

5th Avenue owners who want better performance or improved exhaust sound should definitely get dual exhaust. Dual exhaust could offer a slight mileage improvement over a freeflowing single exhaust. But I suspect it would take some time for the improved mileage to pay for the dual exhaust.

I know it wasn't asked, but if it was my car, it would get dual exhaust, a good 4 bbl carb., 2.94 or 3.21 gears, and an an overdrive A500 transmission from a Dakota. Installing a cop car suspension under it would be another great improvement. That would make a NICE cruising car!

I haven't checked the ratio yet. The cost of the dual kit alone is cheaper than the exhaust shop running a single setup. Its getting a 4bbl and a carbon off a 360 from an 85 Powerwagon. I also plan to run 215s instead of stock 205s. It currently has 195s. Running cop suspension will lug it down slightly do to added weight. I also plan to go with an electric fan and possibly underdrive pulleys