Superformance Modifications

[Thieleng]

I am working on suspension modifications to SPF2378. Changed out the rubber bushings, put on QA-1's, changed out the spring rates on the coil overs, bought 17" wheels (ugh). The front springs are 10", changing to the 17" wheels keeps the front end too high with the lower profile Kumho's, switching to 7" coil overs 350#/300#. The wheels and tires I will use only for track and autoX. Any experience out there with regard to other suspension upgrades and/or spring rates that help with regard to handling modifications? I ordered the "402" headers and changed out the mufflers to the flow through style as suggested in the forum area. The original headers seemed restrictive as the exhaust port diameter on the Roush 427IR was larger than the supplied exhaust manifolds. Also I am thinking about doing a quick release on the steering wheel so that I can change back and forth from the standard wood to leather wrapped steering wheel. Do you know of anyone that has done this? Any other suggestions for performance/handling mods?

[greg schroeder]

The Superformance Roush 427R combo sure is a fantastic set up as it comes, but you sound like a few of us that want to pinch out a little more.

Your suspension mods sound cool. I picked up a set of the 17s also with Yokohama A032R soft compound. I saw the same tire on a road driven Cobra and it didn't seem to have thrown stones under normal street driving conditions. I found that attractive. I've not yet put mine on the car for testing. I did also get a second set of rear 15s with a slightly different offset of about .4 inches moving the wheel inward to accommodate a 325/50 15 Mickey Thompson ET street drag radial while maintaining a somewhat normal look from an outward view. In doing this I discovered a lump on the fiberglass inner wheel well driver side that rubbed. It was minor fiberglass work and it works perfect now. The passenger side was fine.

"402" headers? I'd like to hear more about these if you know detail. I have a different set from the Olthoffs with 2 inch primaries that have room for the exhaust port width on the 427R heads (AFR 205), but always like to hear what else is out there. I have the 3 inch internal side pipes from Buckshot Racefab coming next week. As a precaution of anticipated increased flow I changed my fuel line to 8AN from tank pick up to carb and installed a higher volume mechanical self regulating fuel pump. Perhaps fuel upsize is unnecessary, don't know.

I thought I'd mention I switched out my air filter. I have the single plane manifold which left room for a slightly taller oval air filter to fit on the aftermarket maid in Taiwan sheet metal base Cobra type set up. That may or may not help, but it looks nice. I picked up a nifty couple of carbs from Pro-Systems too. That so far was the largest improvement to smooth acceleration with the carb they built to run fast in a straight line. Headers, air filter, carb picked up about 35 HP over Roush supplied 750 double pumper as delivered on the car. My second carb from Pro-Systems is one they called a "Trans Am type?" It looks pretty funky and is suppose to allow being tossed all around in corners and stops without issue. I've not put it on the car yet to test.

[greg schroeder]

sorry for all the carb stuff. I just realized I R is injected. Very hot stuff man. Let us know how it goes when your done.