Professional Pipes In Your Driveway!

Lay out the entire system beforehand to assess what you’re in for. We ordered the kit (PN 17107) that fits ’64-’72 GM A-body cars like our LeMans, and chose more mellow-sounding mufflers (PN 52558). They’re thicker than standard 50-series mufflers and more suited for big-displacement engines like our 0.060-over 455. The head pipes are designed for cars with headers, but a muffler shop could simply bend extra-long extensions to attach manifolds. Easily visible is the H-style crossover pipe that does a good job of balancing the engine’s raspiness. Two sets of tailpipes are included; we chose the turned down tails, which are virtually invisible once installed. Reducers aren’t included; ours came with the Doug’s Headers we installed in The Great 455 Swap. Now that you know what you’re getting into, raise the car as high as possible and support it with four jackstands. We suggest placing the rear stands under the axletubes so the rear suspension sits at ride height.

The kit uses factory-style rubber-and-steel frame brackets (arrow) to hang each muffler by its outlet pipe. After bolting the two brackets to the frame crossmember, we supported each muffler on a jackstand, adjusted it to the correct height and position, and loosely bolted up one of the supplied U-clamps to hang it on the frame bracket. Having the mufflers in the right place will make positioning the H-pipe assembly a snap.

The H-pipe is a welded assembly that slipped easily into the muffler inlets. Elevating the H-pipe to the proper height was easy using three sturdy boxes. Note that the pipes bend slightly upward at the rear of the assembly and slightly downward at the front. Our installation is actually upside-down from what Flowmaster recommends, but we found this orientation tucks the mufflers up within 3/4 inch of the floorpan, affording awesome ground clearance. Our method will, however, put the H-crossover closer to the driveshaft, so check to make sure it doesn’t hit.

With half of the system in place, we made sure the mufflers were at equal heights and parallel, shoving wood shims under the jack stands to even ’em up. The over-the-axle pipes and tailpipes were slipped in next.

Flowmaster requires you to trim the oversize head pipes to the proper length to fit your car. First, make damn sure the rest of the system is exactly where you want it. Bolt the reducers to the header collectors and slip the back of one head pipe into the H-pipe assembly. Raise the head pipe, as shown, and mark where you want it cut so it’ll slip over the reducer cone. Remember, the pipe swings in an arc, so you’ll want to cut the pipe a little longer than what’s shown in this picture.

Take one pipe and reducer to a friendly muffler shop, and have it cut and expanded slightly so it slips over the reducer cone. Return to the car, re-install the head pipe and collector and verify it fits. Now, mark exactly where the head pipe overlaps the reducer—the distance overlapped and its rotational position. Take it back to the muffler shop and have the head pipe welded to the reducer. Reinstall the head pipe/ reducer assembly on the car, and repeat the process on the other side. This makes for lots of trips to the muffler shop, but it’s a foolproof way to ensure everything fits perfectly. Really! Doing everything at once increases the risk of cutting one or both of the head pipes too short (like we did the first time). Take your time on this step.

We clamped all the joints together and made a few final adjustments to get a perfect fit. Later, we’ll get the system fully welded at the muffler shop so there’s no chance of rattles or leaks. Crack open a cold one and admire your work—the system looks and fits better than most custom exhausts we’ve seen from muffler shops. Between Doug’s 17/8-inch primary headers and the Flowmaster mufflers, the exhaust note was sufficiently awesome to cause a parking lot full of import guys to stop and stare as we rumbled by, but it’s quiet enough to cruise invisibly past Johnny Law. We love it.

It used to be that the exhaust system was an overlooked part of the total performance package. Look under a bunch of cars at a show, and you’re bound to see a number of 'em with disgusting, rusty, poorly bent, crumpled pipes. The days of rippled, restrictive bends; rust-prone, bare-steel tubes; and glasspacks are over, fortunately. Nowadays, good exhaust means long-lasting, aluminized pipes that stay looking clean and bright for years; smooth-flowing, full-volume mandrel bends; and high-tech baffled mufflers.

Would you believe us if we told you there exists such a system that you can afford, have shipped to your door, and install in your driveway on a Saturday afternoon? Believe it.

We installed Flowmaster’s 2-½-inch American Thunder exhaust system—complete with 50-series three-chamber mufflers—on our ’65 LeMans in four hours. And we didn’t need a lift or exotic tools, either, just four jackstands, simple hand tools, and a little patience. We did have to visit the local muffler shop and shell out $5 to have the head pipes cut and expanded to fit over the header reducers, but otherwise it’s a complete bolt-on. We’re glad we took plenty of pics during the installation, ’cause none of our friends believed we installed such a trick exhaust in the driveway! That about says it all.

Check out how easy it really is.