I've read all about the restrictive nature of the TPI setup, and how it drops off at around 4500 rpm. All of that is on naturally aspirated engines though. How bad does the TPI choke a supercharged motor? Do the tricks of porting out the plenum and intake base do much good for a supercharged application? My bottom end is stock. I have a ZZ4 cam, 30lb injectors, and a stock TPI. The ignition has been upgraded to a Crane HI-6TRC setup with the PS62 coil. I'm gonna install some Trickflow heads this weekend and need to know it is worthwhile to port the intake. I've been reading how Mike Davis siamese ported his base and got really good dyno proven horsepower gains. I'm just not sure if this will help me out at all. Also, is the throttle body a problem? I've been considering the 58mm throttle body, but I don't want to waste time and money if it s really not a restriction to start with.

 

The effects of the TPIs restriction at higher RPM are not nearly as big a deal on a force fed engine as it is when naturally aspirated.
That being said, anything you do to free up flow on the intake side will still improve power production, blown or not. Porting or aftermarket parts will allow more air to reach the cylinders on any given boost level.

Do a search for Preston Smiths '85 IROC with a 305. At one time he was running an intercooled Vortech supercharger on a built 305 (yes 305) TPI with an extrude honed OEM base, large tube runners and a ported plenum. He was going low 10s and high 9s with that combo.

 

My car pulls plenty beyond 6k.

-- Joe

 

It's not that it really falls off at 4500 (if it does then you most likely have an ignition problem, the HEI is notorious for falling off around there), most will rev fine into the 5500-6000 range or more. It's that because of the low torque peak you'll run faster by shifting at 4400-4600 since you'll be applying more torque to the wheels for a longer period.