I agree 100% with mike. I'm just didn't want to be the first one to say so.

I know I'm too nice, I didn't really want to start an arguement.

 

Back to the original question. . . you don't mention what sort of cat-back/ muffler you're using. I've seen FlowSmasher and Spintech really kill horsepower, to the tune of 30 - 40 rwhp loss even in the 3" and 3.5" sizes. The most recent that I've had to add to that list is Borla. Would you believe that a 3" Borla just robbed 100 rwhp from my buddy's combination. That's not a misprint. 100 rwhp by removing the Borla cat-back. It went from 420 rwhp to 520 rwhp just by removing the exhaust.

 

Wow, Thats a hell of a restricted catback. But Unless your friend's application was an all out race application a wide open borla should not take away so much. What was so different about his motor that needed more than a 3" exaust?.

 

A wide open borla is not really a borla then, is it? Just like any other cat-back with a cut-out. . .

 

So what do you guys think the idler pulley on the supercharger being froze and the dyno having a 4.10 input instead of a 3.73 cost me my extra horsepower that i am looking for.

And I have a borla catback with the cutout side blocked off with a 1/2" hole drilled in the plate to cut down noise. The FlP headers i am using the straight pipe instead of the cat's.

 

As long as the belt wasn't slipping (10 psi) the idler won't change it much. Maybe 10 hp.

The dyno measures horsepower at the tire, then calculates torque based on gear ratio. That could effect the torque readings but not hp. Dynojet will give a hp versus speed curve if you don't hook up the spark pickup. If you do hook up the spark pickup, it will calculate the gear ratio for you.

Try removing the Borla plate on the dyno. If it picks up power, I highly recommend Hooker's Aerochamber.

 

On the boost number, 15# pullies will usually only give 10-12 on a 383. The boost/pulley ratio is calculated on a 350, so larger motors will see less. A more efficient motor will show less boost for the same HP also, and boost is more a measurement of restriction than anything.

Your IAT numbers look real good also.

 

opening the borla netted me 32rwhp... would you call that a cut out?