[johnnykool6]

Hi guys, new to the site, and hope this is the right place to ask. I'm new to superchargers, and automatic trannys, and heck... Chevy's too! I've built a '85 S-10 with a 6-71 with twin blower Holley 750dp's atop a LT1-350, hooked up through a 5600 stall, to a TH400, then back to 4.88's with a spool. Power transmitted through a shortened 4 link 12 bolt and 29X18.5 Sportsman Pro tires. I'm hoping this is a "fun " little street truck! Those are the basics... Now... questions are; does the vac. mod. on the TH400 get hooked up to the base of the supercharger, where there is only one vac port which is used and harder to get too, or the base of the carb before the blower, which is easier to get too, and has a few ports to choose from. My thought is the first choice (motor vacuum). Does it matter? Shifting manually or auto? Or can it be left disconnected? And do I have to hook up the electronic kickdown if I plan on manually pulling it down? (should have used a 4 speed!! lol) Thanks in advance!

[Frisco]

A very good answer can be found HERE. Go to post #5 by Joe Padavano.

[johnnykool6]

Thanks, That helps me understand how it works. I wanted to know, through other peoples experiences, where they have theirs hooked up. Since the blower makes vacuum (between the carb and blower) whether at idle or wot, and vacuum to boost as it goes through the rpm range (between the blower and manifold), which is the better spot for the vac. mod. to work best on the street, or doesn't it matter?...

[tubbedz]

My buddy has been through the same dilema...

Blower transmission shifts soft at low RPM's

[Crosley]

you can not hook the vacuum modulator to a port under the blower where boost pressure will get to the modulator.

i hooked my stuff to a port just below the carbs when i had super charged engines

[johnnykool6]

That's the stuff I needed Tubbedz! Also thanks to you Crosley, for my lessons in modulators! You were both very helpful! And thanks for pointing me in the right Frisco