What Size Street Pulley Combo for KB With Built Long Block

[LTNBOLT]

What size pulley combo are you guys running on the street with a KB and built motor.

I have ported heads and Crower stage 2 cams. I'm running a 3.0" upper and 6# lower (9") making 15#'s of boost in normal temps and 16#'s in cool weather. I'm running a safe 12 degree timing tune.

I plan on going to 3.25" upper and 8# (9.75") which should give me at least 1/2# more boost. I already own these pulleys so I'm out nothing.

I'm just looking for info on what others are doing for boost on street combos.

BTW, the combo I've been running on the street is what I run at the track.

EDIT: Did the math on the pulley change and the blower RPM comes out to be the same at 5500 engine RPM.

 

[Thunder Bolt]

An 8 lower and 3.25 upper should make at least 17#'s.

Crankshaft Pulley Dia. / Supercharger Pulley Dia. x engine rpm = Supercharger rpm.

Maximum rpm for racing is 18,000 rpm. = Ratio.

8# lower 9.5 / 3.25 upper X 6000 = 17520 rpm
8# lower 9.5 / 3.10 upper X 6000 = 18360 rpm

I ran a RR 3.1 on my street tune with a 5650 shift point.
I recall making 18-19#'s depending on weather conditions.

 

[Add Name Here]

An 8 lower and 3.25 upper should make at least 17#'s.

Crankshaft Pulley Dia. / Supercharger Pulley Dia. x engine rpm = Supercharger rpm.

Maximum rpm for racing is 18,000 rpm. = Ratio.

8# lower 9.5 / 3.25 upper X 6000 = 17520 rpm
8# lower 9.5 / 3.10 upper X 6000 = 18360 rpm

I ran a RR 3.1 on my street tune with a 5650 shift point.
I recall making 18-19#'s depending on weather conditions.

What he said. I have an 8# lower and I'm at 18 PSI

 

[Derek2001]

I run an 8# lower and 3.5 upper for 15-17psi depending on weather
For race/weekend I run a 8# lower and a 3.0 upper for 20-21#'s.
Stage 2 heads/cams

 

[Fade 2 Black]

Before the JLP plenum which is supposed to add boost:

9"L 3"U=16-16.5#
9.75"L 3"U=18#
9.75"L 2.75"U=20#

I normally don't run more than 12-14# on the street, mainly since it's too much power but I also run 12* timing in my street tune.

 

[Fade 2 Black]

I installed my 9" lower with 3" upper to do some datalogging. The temp is ~57* with pretty high humidity (drizzling) and right after I began the run my gauge was hitting 18# so I aborted. I wasn't at WOT yet btw. I'm gonna have to try the 3.25" upper and see where I'm at I guess. :thumbsup:

 

[LTNBOLT]

I'm running the older JDM long block setup with his Crower Stage 2 high lift (.581) cams.

All I have is a safe street tune with 12 degrees of timing and stock shift points. With a 9" lower and 3" upper SFPH non-slip I am only seeing 15#'s in 70 degree temps and 16#'s in 40 degree temps. I'm sure if I spun it to 6000 rpm the boost would be higher. At around 5200-5300 rpm this is all I'm seeing.

I still need to take the lower intake off and port match it. I guess this thing is really flowing regardless.:shrug:

I do know that this engine ran 10.9-10.8's in 90 degree Dallas heat when it was in Leonard Watson's truck. It had a 8#, 2.75" pulley combo on a KB running a JDM race tune and C16 fuel. Dealerjim ran on average .15 seconds faster with the same setup and JDM's newer (lower lift longer duration) cam setup.