PIPE HYPE

HYPE

BY RICHARD EHRENBERG, SAE

ALL CHRYSLER V8 ENGINES have the firing order: 1-8-4-3-6-5-7-2. So what, you ask—you already knew that. Yet, there’s food for thought in those 8 digits.

Two combustion events take place sequentially on each bank: 8 then 4 are both on the right bank, resulting in the exhaust gasses from cylinder #4 being force-fed in the right-side exhaust system while there’s still back pressure lingering from cylinder numero 8. This can result in cylinder #4 being shortchanged a bit on torque and HP (from incomplete cylinder scavenging). The same artifact affects cylinders 5 and 7 on the other side. The factory, obviously, was well aware of this. Street Hemis and 440 1967–’70 B-bodies were all equipped with an H-pipe, which was a balance tube upstream of the mufflers. Minimizing this effect made more power and torque. It also, to most people’s ears, made the exhaust sound more melodious.

Speaking of exhaust tone, many people are not crazy about stock E-body (non-Hemi) exhaust sounds. This is apparently due to the modified exhaust system the factory fitted into the E’s reconfigured floor pan dimensions. The “resonators up front” setup produced what some find as a harsher tone. This was, no doubt, worse on larger displacement engines due to the lack of a crossover.

Not long ago, we installed a flawless-repro complete stock system from Accurate, Ltd., in a 1971 383 E-Body, with one upgrade request: We wanted 2½ʺ head pipes (standard 440 size). Accurate complied, and the result was very positive and noticeable. This was no surprise, because in the late ’60s Chrysler surreptitiously installed 2.5ʺ pipes on many pressfleet (“road test”) 383 loaner cars.

Why not, we reasoned, install a crossover (balance tube) on this system? We did, and the results were overwhelmingly positive, both in throttle response and a smoother exhaust note. The cost was minimal, and the entire job took only a couple of hours. We devised a slick, neat way of fabricating this. As usual, you can follow along as we put the MiG to the metal.

’67–’70 440 B-bodies all had a crossover (H-pipe) as standard equipment, as did Hemi B- and E-bodies. This was costlier, since fabrication tolerances were tight.

Even better is an X-pipe, as in this killer TTI system. Not easy for duffers like us to fabricate, though.

All other performance-era Mopars had isolated (L/R) dual systems. E-bodies, shown here, were weird: Resonators were up front, mufflers were in the rear, this was necessary due to the unique “sports car” floor pan proportions. Some say this setup resulted in a less-pleasing exhaust tone.

Theory dictates placing the balance tube at the hottest location found on the pipes immediately after a hard run. Reality, however, will require the pipe placed for convenience and freedom from obstructions. In our E-body, this meant placement as shown. As long as the tube is installed anywhere forward of the “first” muffler or resonator, it will do the job. We began with a scrap length of pipe the same diameter at the current system (in our case, 2.50˝), long enough to bridge the gap between the installed system (in our case, less than a foot was necessary). Scribe a line parallel to the centerline, centerpunch a dimple, then drill a small pilot hole in the center. Drill a second hole exactly opposite the first—do your best to locate this accurately.

Clamp the pipe in a vise equipped with pipe jaws. This is a must. Drill using a hole saw with the same diameter as the pipe. This might seem counterintuitive, but it results a really neat job. Hang on!

This is the result of the first surgical incision.

Rotate the pipe 180° and drill the second hole. The pipe will now almost be totally bisected. Cut off the resulting tabs in the center of each (hacksaw).