I recently installed Flowmasters on my slightly modified 460 after years of running Wicked Flows. The truck sounded like a beast with the Wicked Flows and everybody loved the sound, but after ear surgery I found the noise caused me considerable ear discomfort. Some interesting things happened when I installed the Flowmasters. The idle went up about 200rpm and I had to turn the idle down, I show over one inch more Hg at idle now. The truck always had this weird sound when cruising like the carburetion or timing was out. It’s hard to describe but it just didn’t sound like it was running right. That sound is now gone and the engine seems to run much smoother at cruising speeds. I use to get a stumble when raising the rpm up to 2500 while sitting in neutral. You could actually see the tach dip when you heard this stumble or miss. This is now gone. The truck seems to have an increase in performance since installing the Flowmasters but I wont know for sure until I hook up my fifth wheel and take it up a grade. The fifth wheel is about 9K loaded. I just thought I would throw this out here for information.

 

Cool, good to know. I'm coming up on the install time for a performance 460 in a '75 250 and trying to keep it as quiet as I can without killing power. The Flowmaster big block 70s came up in the running alongside Superturbos as options. How do you like the sound now? Ideally I'm after a low toned earth trembling rumble without being so loud that a conversation can't happen within ten feet of the truck. Or waking the neighborhood.

Any chance on a little video?

 

I decided to go with the Flowmaster because of the “Delta Flow” Technology. It may just be hocus pocus but it sounded good and the idea of no restrictive baffles intrigued me. I have about 20k miles on it since installing the Flowmasters. The truck has made five trips from California to Idaho and back hauling a heavy load. There may be a slight increase in mileage since the install but it in minimal. But the increase in performance over the wicked flows is phenomenal. The engine runs better, runs smoother and cooler. The power increase is amazing. I didn’t know a muffler change would make that much difference. You use to have to really stand on it to bark the tires. Now just accidentally tapping the accelerator a little to hard will bark them. I have to be careful when leaving a stop sign to keep from burning rubber you can get a ticket real easy in California for barking the tires on accelerating. I don’t know if you are familiar with the Donner summit in California but trucks pretty much crawl up it. I went over the summit last spring at 65mph with the 9k fifth wheel in tow. I got boxed in by cars a few times behind big rigs and was able to accelerate right back up to 65 when the cars cleared out of the way. The truck is not as loud as it was and you can now hear the radio or talk with a passenger but it has a healthy throaty sound. You can definitely tell it’s a powerful big block when you hit the accelerator. I will try to make a video in the next day or two and post it on here.

 

That sounds exactly what I'm after. We don't have any 6% grades on the pages here, but mountain climbing happens a lot for me and a big reason for having the extra poop. Mostly for the folks that go ten under in the no pass zones and ten over in the passing lanes.

My wife's Mustang has new Super 40s on dual exhaust behind a 302, and while a nice sound for that car, it's as loud if not a bit louder than I want the truck with the headered 460. They do have a tinny sound to them too. Just a touch. The Superturbos have a nice mellow rumble, but there are repeated and understandable reports that they degrade as the glass cooks out. "They'll never be as quiet as the day you buy them" comes up a lot. Hem.

Thanks for the reply, and look forward to the clip. No rush on my account, I'm still at least a month away from pulling the trigger on something. Cheers!