I recently converted spf2122 from street to R, one problem we ran into was with the exhaust in the car last year. We dyno'd the car on a dynojet and were only getting 470 rwhp. The engine dyno showed 615 crank hp so we knew we were lossing quite a bit of hp. This is a 434 CI all aluminum motor with AFR 225 heads. The factory headers are, I believe, 1.5". After contacting Ron Roberts at Fireflyperformance.com ( he had done the pipes on my cobra ) we decided a much larger header was needed. Over the winter Ron made up a new set of 2" pipes out of SS and had them coated for me. Finally got the car on the dyno and picked up 39 hp (with a very fresh trans). Here is a copy of the dyno run. this was performed on the same dyno as before. Unfortunately the previous run's were deleted off the dyno so I cannot give you a full comparison. From a seat of the pants the car has much more power, with street tires, you can spin them in 1,2 or 3rd just by applying throttle. Car completely hooks up with track rubber on it. This was a great upgrade that really lets the AFR heads breath.
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