| Quick Mustang Reference Guide |
| To Flowmaster Mufflers |
| Muffler Type | Part No. | Specifics |
| Series 40 Two-Chamber | 42443 | 2 ¼" in/out Offset Both Ends 19" Overall Length |
| Series 40 Two-Chamber | 42441 | 2 ¼" in/out Offset In/Center Out 19" Overall Length |
| Series 40 Two-Chamber | 42543 | 2 ½" in/out Offset Both Ends 19" Overall Length |
| Series 40 Two-Chamber | 42541 | 2 ½" in/out Offset In/Center Out |
| Series 40 Delta Flow | 942041 | 2" in/out Offset In/Center Out 23" Overall Length |
| Series 40 Delta Flow | 942441 | 2 ¼" in/out Offset In/Center Out 23" Overall Length |
| Series 40 Delta Flow | 942443 | 2 ¼" in/out Offset Both Ends |
| Series 40 Delta Flow | 942543 | 2 ½" in/out Offset Both Ends 23" Overall Length |
| Series 40 Delta Flow | 942541 | 2 ½" in/out Offset In/Center Out 23" Overall Length |
| Series 40 Delta Flow 409 | 842441 | 2 ¼" in/out Offset In/Center Out 23" Overall Length |
| Series 40 Delta Flow 409 | 842443 | 2 ¼" in/out Offset Both Ends 23" Overall Length |
| Series 40 Delta Flow 409 | 842541 | 2 ½" in/out Offset In/Center Out 23" Overall Length |
| Super 44 Two-Chamber | 942448 | 2 ¼" in/out Offset Both Ends 19" Overall Length |
| Super 44 Two-Chamber | 942548 | 2 ½" in/out Offset Both Ends 19" Overall Length |
| Series 50 Delta Flow | 942051 | 2" in/out Offset In/Center Out 23" Overall Length |
| Series 50 Delta Flow | 942451 | 2 ¼" in/out Offset In/Center Out 23" Overall Length |
| Series 50 Delta Flow | 942456 | 2 ¼" in/out Offset In/Center Out 19" Overall Length |
| Series 50 Delta Flow | 942453 | 2 ¼" in/out Offset Both Ends 23" Overall Length |
| Series 50 Delta Flow | 932556 | 2 ½" in/out Offset In/Center Out 19" Overall Length |
| Series 50 Delta Flow | 932551 | 2 ½" in/out Offset In/Center Out 23" Overall Length |
| Series 50 Delta Flow | 932553 | 2 ½" in/out Offset Both Ends 23" Overall Length |
| NOTE: These mufflers apply strictly to Mustang. Three-inch pipe mufflers are not included because they are not recommended due to space concerns. |
Complete Flowmaster Exhaust Systems
Complete Flowmaster exhaust systems are available from Virginia Classic Mustang for classic and late-model Mustangs. If you're doing a classic, there are four basic systems designed to fit: two for '65-'66 and two for '67-'70. All are from the transmission crossmember back. If you have a convertible, you're out of luck because these systems are designed for hardtops and fastbacks only. Late-model systems (not covered here) are from the catalytic converters back (known as "cat-back" or "after-cat") with the H-pipe, mufflers, tailpipes, and all attachment hardware.
The 19-inch Flowmaster Series...
The 19-inch Flowmaster Series 50 Delta Flow mufflers are a perfect fit.
The American Muscle system...
The American Muscle system (PN 17334) comes with the shorter Series 50 Delta Flow muffler, perfect for a frequent-driver classic Mustang. These are 19 inches long with 2 ¼-inch offset in and center out. This is where it gets tricky because '65-'66 Mustang factory dual exhausts are center in and offset out. With the Flowmaster system, there are no worries about offset. If you are fitting them to a factory '65-'66 exhaust system, you may need a muffler shop to tweak your pipes for better fit.
Externally, the Delta Flow...
Externally, the Delta Flow muffler doesn't look any different from a conventional Flowmaster. The difference is inside. Here's a pair of 2 ¼-inch Delta Flow mufflers that are 19 inches long. We had these custom-made by Flowmaster for '65-'66 factory dual exhausts with center in and offset out. You'll have to pay more for this feature, but it's worth it if you want to keep the original pipes.
Delta Flow magic is inside...
Delta Flow magic is inside with multiple deflectors, a resonant tuning chamber, power chamber, and a low-pressure balance chamber. The result is a more civilized Flowmaster muffler with a quieter cabin and less resonance.
The H-pipe, with its crossover...
The H-pipe, with its crossover tube, should always be used with a dual exhaust system to balance cylinder bank exhaust pulses and improve sound.
Pro Motorsports Engineering...
Pro Motorsports Engineering pioneered the X-style crossover. The X smoothes out exhaust pulses and yields better scavenging, especially at high rpm. It also quiets exhaust harmonics and improves horsepower. Don't expect a huge gain in power, however. On average, we've seen 5-15hp improvements. Expect closer to 5 hp. Mix the X crossover as part of your horsepower improve arsenal. It's the little things that add up to big gains. On the street, torque is what you want most.