Flowmaster/Exhaust for 70 mach1 351C

[rbonitz]

I've owned my '70 Mach 1 for 20 years or so, but have only started to modify it since subscribing to this group.

The 351 Cleveland 4 barriel is basically stock except for a mild cam. I'd like to upgrade the exhaust to improve both performance and give it a bit more bark, but I'm not looking for anything too radical.

I've ordered a set of Jet-Hot coated Hooker Competition Long Tube headers and I'm going to have a stainless system custom built.... A couple of questions...

What size pipes should I go with - is it worth going larger than 2 inch with my setup? What Flowmaster mufflers should I go with - 40 Series? - Should I just order ones with same dimensions as the stock mufflers?

Thanks,
Ray

 

[pabear89]

Welcome, Hanging around here might sway you to add even more to it.

I am running 2 1/2 inch ss thru magnaflows and a crossover, their not too loud but will let you know I'm there if I put my foot down.

I did not go with the larger 3 in because I don't like that empty tube sound
that it makes. JMO.

the Magnaflows are talking at 55 mph but as the speed increases the sound quiets down. But I like it.

PB

 

[NorCal66]

I just got my 40 flows on today...I love em. I can feel a definate improvement in throttle response, but I'm guessing that is mostly due to the H-pipe i had put on as well. 40s are very "tinny" sounding and get pretty loud at WOT, they kind of sound like a truck, but I love it. You should go check out www.mustangexhaust.com and www.exhaustsoundclips.com if you're not sure on the sound you're looking for.

As far as pipe diameter goes, I'm pretty sure a thinner pipe will produce better low-end, while a wider one will let the car breathe better at higher RPMs. Too big of a pipe on a car that doesn't need will actually let too much air from outside back into the exhaust. I went with 2.25" dual pipes on my mild/med 302. If you're planning on more engine mods in the near future you should take that into consideration as to the diameter of you're exhaust. As I said, I'm pretty sure on this but not positive, I'm sure one of the more knowledgable posters will come and confirm/correct this.
Good luck!