Need exhaust design help

Is your engine built? IE: performance heads, performance, cam etc? I ask because that speed demon 650 really flows over 750cfm and you are probably losing a lot of power. I would suggest some hooker long tubes ( 1 5/8" primaries), mated to a 2.5" DR gas xpipe, spintech staggered inlet/outlet mufflers, through 2.5" dr gas tailpipes.

Shane

TruckeeFastback said:

68' Fastback need a whole new exhaust from the heads back. It's got a 302 w/ Speed Demon 650, and RPM Air Gap on it. The car is going to get lowered so I think I need shorty headers.

What about a crossover? How about (2) glasspacks on the long run down the driveshaft and then a 2-in, 2-out Flowmaster like the Shelbys. Or how about staggered 1-in, 1-out Flowmasters on the long runs. What seems to work best?

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I used long tubes on my lowered '65 fb without problems. Suspension was stiff which helped. Emergency brake cable clearance is one thing to consider when installing the mufflers. I used Dynomax but I'm sure there are other performance mufflers that are equally good. Mufflers can be individually mounted in the recesses in the rear floor or transversely. Straight throughs aren't as good as one might think. 302's seem to be just as good with 2.25" tailpipes as 2.5"s. Note that both Holley and Edelbrock list 2.25" as their recommended size for 302's. This doesn't hold true with 351w's since the displacement is greater. They need the extra diameter.
Smaller tubes are easier to fit. Take the job to a pro shop. It will cost you a very little bit more but hey, its no sweat and the job is cleaner than pieced together kits.

Headers into crossover (custom H) and 2 flows right before the axle, bends over the axle into tailpipes is what I have, sounds great. Most people use an X pipe with straight thru mufflers and an H pipe with chambered mufflers. An X is apparantly good for a few more ponies, but it's quite a bit more expensive. Check out
www.mustangexhaust.com
www.exhaustsoundclips.com

if your not sure on the sound you want.