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Installing a 3-Inch Flowmaster Exhaust - Quick Tech

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Installing a 3-inch Flowmaster Exhaust
After we bolted the Lester Scruggs 404ci engine into our Orange Peel '66 Chevelle using Edelbrock motor mounts and headers, it became obvious that the leftover 21/2-inch exhaust system was due for an upgrade with a Flowmaster American Thunder 3-inch exhaust system. Since Lester makes a serious 560 hp, a 3-inch system seemed an ideal choice. We plan to put miles on this Chevelle, and 3-inch systems are notorious for their bellicose exhaust notes.

Normally, the Flowmaster American Thunder kit is shipped with a pair of 40-series mufflers, so we opted instead for a pair of larger (and yes, heavier) 70-series Big-Block II pieces with a pipe kit (PN 1033). The Big-Block II mufflers are 9 inches longer than the 40s, so squeezing them under the car was going to be a challenge. We decided that Kevin McMillan at McMillan Speed and Fab has far more talent than we do, so we took the Chevelle to his shop and spent a day massaging the pipes. An exhaust system may not be very romantic, but when installed correctly, it will enhance not only the sound but the fun of driving. Our 3-inch system is rock solid, virtually disappears under the car, and sounds fantastic. It doesn't get much better than that.

DESCRIPTION PN SOURCE PRICE
Stainless V-band clamps, 3-inch Call McMillan Speed & Fab $65.00
Flowmaster 3-inch system 17202 Summit Racing 615.95
Flowmaster 70-series mufflers 53073 Summit Racing 271.90
Flowmaster pipe kit 1033 Summit Racing 528.95

A. McMillan added O2 sensor bungs aft of the Edelbrock header flanges on both sides so we could keep track of the air/fuel ratio.

B. The Edelbrock LS engine swap headers offer a straight shot from the collectors to the large 70-series mufflers but sacrifice ground clearance. We found a set of Hooker LS swap headers that fit much tighter to the floor, producing an additional 2 inches of ground clearance that now need to go in the car.

C. If this system is hard to see in the photo, it's because McMillan painted the entire system flat black to make it blend in easier with the underside of the car. It's amazing how a small step like this makes the installation more professional.

D. McMillan fashioned small L-shaped brackets that use a shock absorber polyurethane isolator to locate the tailpipe without noise. The entire system is ridiculously rigid with zero rattles.

E. The original Flowmaster system exits just behind the rear tire, but we decided the tailpipes needed to exit farther back to look correct. McMillan used an 11-inch section of pipe removed from the lead-down pipes near the headers to extend the tailpipes.

SOURCES
McMillan Speed & Fab
Oxnard
CA
805-278-3900
www.speedandfab.com
Steve Watt Enterprises
Ventura
CA  805-798-09
www.maxwellindustries.com
Flowmaster Inc.
100 Stony Point Road
Suite 125
Santa Rosa
CA  95401
800-544-4761
www.flowmastermufflers.com
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