Q-jet and Holley

[Alan Roehrich]

Originally Posted by vic guilmino

i removed a 780 holley and
i put a q-jet on my 429 ford
same mph but et was .2 slower
carb when very rich in the first 100'
need help with that

Vic, does your carburetor have the little air deflector on the top behind the choke horn? Often you find that the combination of a slightly high float level and that little sheet metal deflector not being there will allow fuel to splash out of the bowl vent and into the secondaries.

If you do not have it, the best book for the Q-Jet racers may possibly be the book Doug Roe wrote, it's available from HP Books.

http://www.amazon.com/Rochester-Carb...4497285&sr=1-2

[Ed Wright]

The two holes above the rear upper throttle blades may need restricted. On larger engines they can often be plugged. They act similar to an accelerator pump for the secondaries. Might try tape over those holes for a pass to see how it acts. If it stumbles with them plugged, you may need to restrict them.

[Adger Smith]

I have used toothpicks in the holes.

[eddie c]

Originally Posted by Mickey Whaley

Q jets are funny get a good one it really will be a surprise the difference!

My apologies for going a little outside of this thread, but I have always
wondered why some QJs perform much better than others. I realize there could be many theories on the subject, what makes one QJ fly and the other a dog! tks ed

[Weekend Racer]

For myself I have a bone in my engine ,it is the Q-jet, or a distribution problem from the spacer and intake.

I hope , I am not the first one with an drop of performance when we switch the Holley for the Q-jet?
Thank,

[Alan Roehrich]

Originally Posted by Weekend Racer

For myself I have a bone in my engine ,it is the Q-jet, or a distribution problem from the spacer and intake.

I hope , I am not the first one with an drop of performance when we switch the Holley for the Q-jet?
Thank,

Sounds like maybe you need to see about borrowing another carburetor, and maybe talk to someone about intakes and spacers. I think a 35HP loss is far too big a difference to be acceptable from just a carburetor change, if the two carburetors are close to the same size.