I had originally planned on waiting a while but I can't stand it. I need power !!! If I build a big valve C headed 9:1 ish mild cammed W/Z manifolds 455 how bad would i be killing it with 2 1/4" exhaust system I have now?

 

I think you would be fine. Its something you can always change later if you feel 2-1/4 is to restrictive. I ran 2-1/4 in my 57 with the 455 for a while until I saved the money for a new exhaust system (the old one had restricted bends) and the 2-1/2 with the mandral bends did improve performance

 

I had a Meineke 2.25" exhaust and the short case DynoMax Super Turbo mufflers on my 70 442. The 455 is mildly warmed over with a 20-22 cam, O4B intake, and W and Z manifolds. The pipes have compression bends and wrinkles in them.

I put in a Torque Tech 2.5" system with long case DynoMax Super Turbo mufflers.

There are two major differences: The exhust sounds deeper and louder, and the power level is noticibly higher. My bet is I picked up 25-30 RWHP.

The Torque tech system fit like a glove. It took me 45 minutes to install it in the driveway. Good product!

 

Thanks but I'm not going to trust any A-body universal kits any more been there done that. My car to too low and the tires are too big. I will have to go custom again.

 

Maybe plumb an X pipe into your existing system as an experiment that wouldn't cost a whole lot. Probably eat up a half day of fitting & welding doing it yourself but you're not out a bunch of $$ if result is less than stellar. Would a 2.5" mandrel bent system be better? Probably, even definitely, but $50-100 if it works, might arguably be close to result of $700-1100 for custom mandrel system that has to squeeze through manifolds to begin with. If you were to run headers, no question - right to 2.5 system, and I believe X pipe is a benefit. I happen to like the sound from X pipe system but it does raise the pitch of exhaust tone a little + pulses sound different. Might want to do some listening to other Olds & take into account manifold type, Exh x-overs filled or not, cam, muffs, X pipe or not to make sure you like the sound - if you're fussy about it.

 

hey gear i will send a video of my 442 so you can hear what hes talking about with the h pipe i have one installed on my car lol http://www.youtube.com/watch?v=aptjNhaiXdE

 

http://spintechmufflers.com/spintech...%20Muffler.jpg Try oval pipes for clearence issue found these guys in hot rodding can put some nice 5 inchers on there with a muffler 2 1/4 inch thick.

 

The nice thing about "X" pipe duals is that you can go 3 inch duals and not be losing any power if you had 3 inch true duals.

There is a HP to exhaust size ratio chart on the net but I can't find it. I remember it was on a Ford board

 

I think you'll be choking it out a bit.

I gain a second and a half at the drag strip when I remove the 2.25" exhaust and stock air cleaner.