Flat Lining boost

**mrtbolt64** · 10-23-2007, 05:28 PM

Here is the combo

393 sbf
Canfield heads 300/200 cfm at .600 lift
232 @.050 int, 249 @.050 ex, .603 int/ .578 ex, 116 c/l hyd roller
Super Vic EFI, 90mm tbody,
8.9 compression
BS3 EFI

Novi2k 7"crank. 3" blower pulley, 3" tubing ran into inter cooler and out to engine, this intercooler http://cgi.ebay.com/ebaymotors/Water...spagenameZWDVW

On the dyno the car only made 475 to the wheels, they would start the run from about 4500, at that point it would only make 6psi thew the 6500 redline. I have yet to check what the psi is before the intercooler but it seems as if the intercooler is resrticting it. With the 7" crank and 3" blower pulley i figured I would be closer to 12 or so lbs of boost, not 6. Weird gow the boost would flatline and not increase with rpm.

Anyone ever run into something similar?

***speedytang*** · 10-23-2007, 10:15 PM

That is a lot of cylinder and head size to fill and same with the cam size on releasing pressure. I really would think 8psi tops myself. If the intercooler was not big enough you would show a higher boost number not lower. Your not spinning the blower fast enough. On a 302 with 165cfm heads Yes you would see 12psi but not with that 393ci and those heads.

**mrtbolt64** · 10-24-2007, 08:38 AM

Originally Posted by speedytang

That is a lot of cylinder and head size to fill and same with the cam size on releasing pressure. I really would think 8psi tops myself. If the intercooler was not big enough you would show a higher boost number not lower. Your not spinning the blower fast enough. On a 302 with 165cfm heads Yes you would see 12psi but not with that 393ci and those heads.

Slowstang101 had this, 393 AFr 205 / TFS BOX 7.4/3.2 A/W cooled 12psi 650rwhp

His final blower speed is 53000 roughly and mine is almost identical for mathcing rpms at 6500.

I am wondering if I have the belt tight enough

***speedytang*** · 10-24-2007, 01:34 PM

I figured you checked for belt dust before posting. I still don't see 12psi with only a 7" and 3" with that much pressure area and if you did it would be at 7200-7300 rpm. PSI is based on restriction/back pressure so your 6psi could produce the same power as a 10psi on a free flowing engine. When I calculate a 8" pulley with a 2.75 blower pulley I get 11.2psi at 6600 rpm. All these numbers are generated on parts selection including exhaust and cam profile. Not a really perfect science without all the data but I figured your Intercooler at 70% efficient.

**mrtbolt64** · 10-29-2007, 07:51 AM

Alright, swtiched to a 3.25 blower pulley with the 7" crank, tightened to hell out the belt and was rewarded with 13lbs of boost at 6600. Now I need to get the overheating figured out.

Thanks