Superformance Exhaust

wanab5150 · #1 (**permalink**) 06-27-2009, 09:38 PM

I certainly understand the quieter pipes and if I had not heard the 3 inch mufflers and found out how much HP is lost because of, in my opinion poor set up, then I would have been happy. Fortunately or unfortunately, I did find out!

I went the extra mile for the Roush 427R and assumed the superformance dealer would provide a correct set up for the engine they recommended to me.

I paid extra for a bunch of options such as the 17" wheels, non standard color choice, seat modification, and more. I would have sprung for a correct complete exhaust system if I had an inkling it didn't match up to the Roush motor.

If I only wanted 400 HP, I would have just put the Roush 347 inch motor in it and saved a bunch of money. Even the 347 makes 450 HP.

As far as the headers go, the heads on a 402 have smaller intake runners and intake valves. I can't imagine the exhaust port would be the same on both heads....what would be the use? larger intake runners and valves require larger exhaust ports and headers unless you want all torque and no top end HP.

If what you say is true, I still need a larger header. I would feel a little better if I knew I had a header more set up for my engine like yours. I might even pass on larger headers if the size difference in relatively small. Still investigating!

thudmaster · #2 (**permalink**) 06-27-2009, 09:46 PM

Tom, the 402 headers are much larger than the standard superformance headers. They match your roush heads.

wanab5150 · #3 (**permalink**) 06-27-2009, 10:22 PM

Ed I hope so. I will ask Steve in Reno tomorrow.thanks

decooney · #4 (**permalink**) 06-28-2009, 12:22 PM

Jim,
Your car sure sounds incredible after you made the change.

I have been meaning to ask you, did you notice any change in the low-end performance with less back pressure, worse/better?

When I redid my exhuaust, I was certain I would lose just a little low-end grunt, and to my amazement it gained low, mid, top end performance across the board. Just wondering how it was with your motor setup. DC

Jim Norris · #5 (**permalink**) 06-29-2009, 05:00 PM

Quote:

Originally Posted by decooney

Jim,
Your car sure sounds incredible after you made the change.

I have been meaning to ask you, did you notice any change in the low-end performance with less back pressure, worse/better?

When I redid my exhuaust, I was certain I would lose just a little low-end grunt, and to my amazement it gained low, mid, top end performance across the board. Just wondering how it was with your motor setup. DC

Duane,
Thanks for the compliment. I do like the sound.

As for the low end performance, I did notice a seat-of-the-pants decrease. I don't know what the numbers are, but the neck-snap seems milder. However, as the RPMs increase so does my grin.

decooney · #6 (**permalink**) 07-06-2009, 12:12 PM

Quote:

Originally Posted by Jim Norris

Duane,
Thanks for the compliment. I do like the sound.

As for the low end performance, I did notice a seat-of-the-pants decrease. I don't know what the numbers are, but the neck-snap seems milder. However, as the RPMs increase so does my grin.

Hey Jim,
After you changed the pipes out, did you have to rejet the carb at all?

I had to go up 4 jet sizes on primary and secondary. If not, there may be little more to be had there...