Did i ever mention Doug Roe's rochester books? Find them at amazon, the first printing (1971?), I think, is the best as it has a bunch of mono, and model B one bbl stuff too. His book predates anybody's q-jet info.
Mostly made in the 750 size with a few 800s (some buicks and Pontiacs for sure)only diff is on the primary side. Air valve is an easy adjustment there are "wind-up" specs available to get you in the ball park(if they are too "loose", they will bring a 455 to its knees). All the back barrels have a pair of 2.25" (57mms in Weber talk butterflies, the 750 jobbies have little 1-3/8" butterflies (35mm)for real nice stumble free low end performance.
Doug shows you how to bore out the accellerator pump well and install a larger accel pump out of a 2GC (po' boys 50 cc holley answer). Most back bbls have a spill port which comes in when the back bbls are opened (Q-jet version of a "double pumper") Not too many trick hot rod Holly features are missed or not incorporated in a stock Q-jet (rochester dont need to advertise this stuff 'cause the sell every one they make to GM). The back barrel meetering rods have different cams to change the lift rate of these rods (thus richness per throttle position).
Doug's book says the models on which the air valves/sec butterflies dont open all the way were done that way to even-out a distribution problem that a particular manifold had-- not to restrict the airflow. The air valve and its shape would then try to direct more airfuel mixture towards the front of those manifolds--Didn't Ruggles ever say that?
They are VERY good carbs- just study them a little. BUY DOUG'S BOOK.
Last edited by preacher-no choir; 10/20/11 01:53 AM.
