Getting the QJet secondaries to open faster...
 

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

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.

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.

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.

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.

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 :)

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?

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"...