Originally Posted by Cab_Burge
I'll provide some at the track results from two of my cars, both wedge powered, not hemiroid powered, with the muffs and pipes on versus no muffs and pipes removed.
Example #1 was my 1969 Dart GTS 440 powered street and strip bracket car at LACR 1/4 mile back in the late 1990s or maybe early 2000, the car ran 12.29 ET at 109.4 MPH with a new set of M/T 105x28.5x15 with 11.0 lbs. in them on the first run at around 6:000 PM on a Friday night T&T with the 2.5 inch exhaust system that consisted of a set of Hooker 1 7/8 A body fenderwell headers hooked up with about 16.0 inches of 2.5 head pipes to a set of Thrust 2 1/2 inch in and out Corvair Turbo muffs with a set of 2.5 inch side pipes going over to the rocker panel directly in front of the rear tires. 2nd run was with 10.5 Lbs. in the slicks 45 minutes later with no other changes, the car ran 12.27 at 109.5 MPH, the last run that night was around 9:00 PM with 10.0 Lbs. in the slicks which resulted in a run of 12.23 at 109.7 MPH.
This was a 3 day event with T&T on Friday night with the gates opening at 4:30 PM , first TT at 6.:00 PM stopping at 10::00 PM. Saturday the gates opened at 8:00 A.M with the first TT at around 9:00 :AM, closing at 10:PM Sunday had the same schedule with closing at the end of racing.
I got to the track around 9:00 AM and removed the exhaust system from the headers back and let the tires down to 9.5 Lbs. with no other changes and made the first TT run around 10:30 AM, it ran 11.39 at 117.6 MPH shock I didn't believe it so I made another run at around 11:10 AM on the other side (L/S) of the track, which with that car was normally around .02 to .03 ET slower. It ran 11.42 at 117.7 MPH work
I did some similar testing with my last street and strip car at Madras, OR a 1/8 mile track it had a pump gas 512 C.I. low deck stroker motor with a six pack and a complete 3.0 exhaust system with the same Hooker headers off of the old Dart fed into 3.0 inch pipes ran to the rear of the car with a set of Magna Flow muffs that where 3.0 inch side inlet by 7.0 inch thick by 14.0 oval with a 3.0 inch center outlet with a piece of perforated straight through pipe in it, the muffs where mounted at the rear bumper with 45 degree turn downs straight out of them. That car ran a best of 7.01 ET at 95.3 MPH with the system on and it picked up to 6.98 ET at 95.5 MPH with the complete system removed confused I'm thinking the weight was where the small perforamnce gains where made, not the exhaust system restrictions work shruggy
Happy Thanksgiving to all up




Thrush turbo mufflers really kill power if you're making some. I had a set on my Plymouth, and I spent 3 summers chasing various issues that made the car just feel like it was 100 HP down from where it should have been. Finally one of the last changes was mufflers (changed to Ultra Flos) and the car felt night and day different.

There was actually an episode of Motor Trend's engine masters some time later and they found that the Thrush mufflers were the worst of all the Turbo mufflers tested. Mine sure did sound good though. They were the Thrush Hush, which is different than the California Turbo model.

Last edited by GTX MATT; 12/23/19 11:47 AM.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street