V8Astro Captain

iTrader: (1)

Are there any good ways to get the secondaries open sooner on a QJet? My blower really likes those giant secondaries. I think I could benefit from them opening sooner.

thanks

Fast355

iTrader: (2)

It is detailed in Doug Roe's Rochestor carb book as well as How to Hotrod Small Block Chevy's. It basically gives you secondary opening starting at about 1/2 throttle.

Sonix

iTrader: (1)

If you snap the throttle to WOT, and want them to open faster;
-less tension on the AV, but you will have to play with that to keep away a bog (richer rods help offset that as well)
-may need to move your "secondary acc pump" shooters to below the air valve flaps. (see the Roe book for more info on this one)
-cross drilling the secondary enrichment tubes. This is mentioned in a few articles, I tried it, but undid it. In retrospect (and with supervisor42's advice), it'll just let the secondaries pull air instead of fuel sooner, so...

-drilling the restriction in the vacuum break to let it use the secondaries in 3/4sec rather than 2.5sec or so.


If you want the secondaries to come on sooner, ie, at a lower throttle percentage (like fast is saying), that's just bending linkages really.
The vac break one is a good one to try IMHO, search on the forum, i've posted on this, and Lo-tec posted a nice picture of it.

V8Astro Captain

iTrader: (1)

I see why you refered me to the Doug Roe's book. Kinda tought to explain that one second-hand.

I'm going to try that and enlarging the vacuum break bleed by a tad. I know, a little bit makes a huge difference.

V8Astro Captain

iTrader: (1)

I got it working fine. All 5 lbs of boost comes on quick. Now I need to make a new accel pump lever for more squirt.

Sonix

iTrader: (1)

You got what working fine, the blower or the vac break or...?

The lever probably isn't the problem. You can use a different pump itself, enlarge the shooter nozzles, grind down the pump top (to give 3/32" more travel) etc etc. If you move the leverage in too far, you may bottom out. So rather then increasing the Z, increase the radius

V8Astro Captain

iTrader: (1)

I got the secondaries to open sooner. That works fine...

I ground down the pump shaft as well. I read that in the QJet book.

How do I go about increasing the radius? Or for that matter, enlarging the shooter nozzles?

Sonix

iTrader: (1)

shooter nozzle probably isn't a problem, but that'd be drilling. I'd leave that 'till dead last.

If you have the q-jet book (doug roe) handy, then I refer you to:
Page 128. You drill/bore out the hole for the pump well. Also, opening up the fill hole a tad might be worthwhile, also on the secondary pump bowls as well.
Also see the picture at bottom of page 124.
Damon runs a roots below his q-jet, he should have more detailed info for ya.

I need to get the book "how to hot rod the small block chevy"...