Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: RLEBird on February 25, 2009, 04:28:35 PM

Title: Dual-plane intake manifold divider plate
Post by: RLEBird on February 25, 2009, 04:28:35 PM

What are your thoughts on notching the secondary divider on a Performer RPM manifold that's using a Q-Jet?  I know Jim Hand discusses the benefits in his book, and Crosswind manifolds actually come that way.  Also, I have a 1" spreadbore spacer, which I'm considering removing the material between the secondary openings.  What do you think would work best for the street?

Title: Re: Dual-plane intake manifold divider plate
Post by: Cliff Ruggles on February 26, 2009, 08:22:52 AM

Use extreme cautioun with any modifications to the divider.  We have recorded some significant LOSSES in power taking out the divider or even modifying them.  A small notch or divit between the secondary throttle plates is fine, or use an open gasket.

The effectiveness of a spacer can only be measured with dyno and/or track testing.  I've done a lot of this here, and the only spacer I've tested which showed some improvments at the track was a semi-open spacer.

4 hole, fully open, and fully divider spacers ran SLOWER at the track on my 455 than no spacer at all.

The semi-open spacer still ran .02 seconds slower, but almost 2mph faster......Cliff