I want to improve the original exhaust on a 1973 302 Mav. It was in storage for 21 years and has what I believe is the original exhaust system. It has a single two inch pipe from the Y to a resonator. Behind the resonator it actually reduces to 1-3/4", goes above the axle and back down to a cylindrical baffled muffler which seems to have a 2" rear outlet but has a clamp-on down turn that is 1-3/4". I don't want to go to duals at this point so I am planning on cutting ahead of the resonator, removing everything back of that and installing a two inch pipe around the axle with a 2" straight through muffler similar to a Thrush and then a short 2" down turn. Two questions: was that really how it came from the factory and does anyone have a alternative solution other than duals or coming out the side ahead of the wheels.
Yes, it came that way from the factory. You should really go with duals, but at one time many years ago I had a turbo muffler installed where the resonator was, and eliminated the resonator and the original muffler at the back next to the gas tank. I then put a dual "Monza" chrome tip on it exiting just a couple inches past the valance.
Definately go with the shorty headers from summit, if I could do mine over, thats the route I would go, better than the long tube headers I have now, IMO.
yes, I tried a set from Pete's brother, the only problem I had (on my car) was they interferred with my rack, but that was only because I installed my rack to fit the long tube headers, If I would have had a set of these shorties when I was doing the rack install I woulda been able to make them fit, no sweat.
If you're not going to be using smooth bent mandrel bent piping?.. use at least 2.5" piping due to the crimp bent piping losing diameter in those areas. Using a 2" crimp bent pipe will end up around 1 5/8" at the crimps. You're also wasting much potential flow and efficiency if you use a tiny 2" muffler too. Go as far forward as you can, all the way to the Y-pipe, and you will get the most gain possible without actually replacing the Y-pipe or going true dual. The difference between my version and yours will be extra throttle response and about 4-6 ft/lbs more torque. Will be even more if you tune the ignition and fuel curves to maximize the gain.
Most people go too big on the exhaust pipe size on a stock motor a 302 is a small motor go with dual exhaust over any single pipe you will be glad you did
This is true to larger degree on full dual systems but would be much harder to be too large on a single exhaust setup. 2.5" single after the y-pipe is still small for a 300 cubic inch engine. In fact, a very well designed single pipe system with.. let's say 4" piping.. shooting out before the rear tire will make more average power than running 2 separate 2.25" pipes over the rear axle. The primary reason being that increased frictional losses from more interior pipe surface and more bend area(further frictional losses) ends in reduced scavenging affect/increased pumping losses and causes an overall efficiency loss in a dual setup. But.. people seem to love that lopey sound of an overly large true dual system and have a tough time fully understanding what that lopey sound costs them in the long run. Even moreso true when it comes to cam choice but that's a whole other discussion right there. And many get both wrong which only gives a narrower/peakier power band that does not bode well for a heavier street car carrying passengers around. The bigger problem comes from those who use headers with 3" collectors on stock/mild 302 cid applications and ALSO feel the need to use too big a pipe diameter which only just serves to add insult to injury. As many have seen firsthand.. sounding tough and being tough can be very different things.
Thanks for the input everyone. I got back in touch with Dyent and ended up purchasing his 2-1/4" single exhaust system with a Thrush Turbo muffler, 2-1/4" over the axle to a straight- through muffler and chrome tip. It sounds excellent and should be much less back pressure than the 1-3/4" system. The system was from a Arizona Comet David had purchased and brought up to Vancouver, BC, Canada. I believe David is going with new duals. My car is in Cranbrook, BC, about 1000 miles away so David shipped it VIA greyhound after removing it from the donor car. He did an excellent job in packing it up to survive the freight trip on the bus. Jim, the local muffler guy installed it in just a few hours. For those fans of dual systems, yes, it is the way to go, but I like my sleeper look, the simplicity and the low cost. Maybe later! D.M.
