Words And Photos: Jeff Smith

I recently purchased a ’64 El Camino with the worst sounding exhaust note I’d ever heard on a small-block car. It could be best described as a cross between a boat exhaust submerged in about three feet of water and a lame 1960’s B-movie sound track. It was horrible. I bought the car because it was a good deal with a dead engine. Once we dropped a mild 383 into the car, it was time to address the exhaust. The exhaust note was so bad I had little desire to drive the car until it sounded healthier. The best way to accomplish this was to dump the entire exhaust system and start over. I had a pair of headers from a previous Chevelle build so the plan was to install them in place of the stock iron manifolds and bump the power at the same time.

Exhaust sound is a very personal decision and I’ve always liked that unique Flowmaster timbre. I decided on Flowmaster’s American Thunder series because there’s a specific, well-designed system for ’64-’72 Chevelles. The big question was which mufflers to order. The standard kit is part number 17119 which comes with mandrel-bent 2.5-inch tubing including a pre-welded H-pipe center section and a pair of Super 40 mufflers. Flowmaster describes these mufflers with their highest rating – “powerful” which simply equates to as loud.

I have had good experience with Flowmaster’s larger, 70 series mufflers that are quieter yet still retain that characteristic Flowmaster sound. Because I’m a bit long in the tooth, a less aggressive exhaust note is a plus. If I was 20 years old, the Super 40’s will be just right! If you want to substitute a different muffler, Flowmaster offers that option with a complete pipe kit that allows you to order the muffler you desire. But make sure you order the right ones. I thought I ordered the correct 70-series mufflers (PN 52573) to go with the original kit, but as we’ll see, that’s not what happened.

The Flowmaster boxes showed up at my shop door and I set up a time with my pal Tim Moore to do the installation at his shop since he had the tools necessary to do the job. The first thing we ran into is that the trapezoidal floor of the deep oil pan on my small-block was just wide enough to prevent the headers from squeezing in from the bottom unless we yanked the engine.

After struggling with the driver’s side header for two hours, it refused to squeeze past the wide oil pan. Because my car was tying up my buddy’s hoist, we didn’t have the time to pull the engine. So we punted and re-installed the stock manifolds. The smart move would have been a set of shorty headers. I also discovered after looking at the Flowmaster catalog more closely that they also make full-length, Scavenger Series Elite stainless steel headers for a Chevelle. Perhaps that’s a goal for later.

By this time, the old exhaust was laying on the shop floor as we opened the Flowmaster boxes. That’s when I noticed that I had ordered the wrong part number for the 70-series Flowmaster mufflers. I was exactly one digit off. The correct part number requires a full offset muffler (inlet offset to the inside, while the outlet fully offset to the outboard), but the number I ordered combined a center-inlet with an offset outlet which won’t work with the American Thunder system. Luckily we had a pair of the Super 40 mufflers with the correct offset so we went with those mufflers and charged off to complete the installation. Had I double-checked the parts and applications when they arrived to make sure they were what I thought I ordered, I could have corrected the mistake before I showed up at Moore’s shop. So it was totally my fault. There’s the lesson for the day – always double check your parts.

Moore did his usual great job installing the American Thunder system even with the hassles of adapting the lead-down pipes from the exhaust manifolds. Our story will reveal the tricks he uses to make the installation easier. Once the system was installed, and I’ve put about 150 miles on it, it’s leak-proof, solid as a rock, and doesn’t rattle – which is critical. It also tucks up underneath the car so well you have to put your eyes at near pavement level to catch a glimpse of the tail pipes! The best part is that while the Super 40’s are a little louder than what this old guy would have chosen, it has completely changed the car’s character. Now instead of showing up at the Friday night cruise site sounding like Popeye’s tugboat, that Flowmasters announce our presence with a nice throaty growl. It’s already garnered plenty of attention – all of it good.

Parts List

Source

Flowmaster
flowmastermufflers.com