Hot Rods Need Quadrajet help

Mark - is it possible the folks trying to tune on the dyno are trying to do it with jets and rods, without making the other necessary modifications?

Cliff Ruggles made believers out of some of the dyno folks after they had made runs with his Pontiac 455 and the Q-Jet he modified.

The dyno operator told him "very impressive, now lets see what this engine will do with a REAL carburetor"!

He put on their test Holley that they used on engines of this size, and made runs with it. No matter what they did to the Holley, they never could get either the torque or power that the Q-Jet provided.

There is more to tuning than just changing jets and/or rods.

This instance pitted a Holley expert against a Q-Jet expert, and the Q-Jet expert won.

Doug's book on Rochester carburetors is required reading for those that work on them; but having read his book and Cliff's book cover to cover several times, Cliff's is MUCH more "user friendly". (Cliff - that is another cup of coffee you owe me )

Cliff was "pretty successful" at the strip as well.

Jon

 

@carbking are you familiar with Lars Grimsrud? He’s well known in the post HAMB old car Q-jet world. I had him do one for my 350hp vette a few years ago. Ran great.

 

Have not spoke to Lars in decades.

Yes, he is also well respected on Q-Jets.

At one time, Lars was president of GTOAA, if my memory is correct.

Jon

 

I used to do a few when we were involved with the HP Pontiac project car.
I'd ship one half way across the country and then one guy would call me and say it's flooding.. Gas all over the place.
I'd have him ship it back,...then sure enough, the needle and seat is full of trash. I'd pick up the return shipping, and before long , he's back on the phone with the same problem. I told him he better familiarize himself with taking one apart. That cured me from doing mail order carbs. ;-)

 

Actually, you can. This from my website:

BRASS FLOATS

Many mechanics have been conditioned to ask for a float each time they rebuild a carburetor, due to the reasonable price of modern, mass-produced floats, and the propensity of nitrophyl (foam) floats to absorb gasoline after time. In dealing with older, NON-CURRENT-PRODUCTION brass floats, neither of the above are true, and a mechanic should attempt to 'save' the float if at all possible.

The first step is to clean the float and inspect it for obvious damage. Small dings and dents are quite common, even in unused floats, and occurred when the manufacturer shipped the floats in bulk. Major dents (generally caused by water freezing in the carburetor) are not generally repairable. If one can hear liquid sloshing around inside the float, skip to the next paragraph. If the float looks to be reasonably damage-free, it should be tested. Testing is accomplished by grasping the float arm with a pair of needle-nose pliers, and submerging the float in very hot water. The hot water will pressurize the air inside the float, and a leaky float will blow a stream of bubbles.

If the float should need repair, it is important to understand how the float was originally produced. Virtually all brass float pontoons (the floating part) are composed of two pieces (a few are more) of brass soldered together. The pieces differ in the seam area, as one piece has a male seam and the other a female seam. One float piece will also have a small hole for temperature equilization. This hole will be covered by a small drop of solder, and will be as far from the seam as possible. The manufacturer would solder the two pieces together, allow the float to cool completely, AND THEN close the equilization hole. Soldering MUST be done using a soldering 'iron'. Repair should not be attempted using either a torch, or a soldering gun. If you plan on disregarding this advice, read the next paragraph first! The following procedure works for us (no, we will not repair your float unless we restore the entire carburetor): First, if liquid is present inside the float, find the hole, and remove the liquid by placing the hole down inside the hot water. The pressure will force the liquid from the float. If the float has much liquid, it may be necessary to remove the float from the hot water, allow the float to cool, and repeat the hot water dip. Once the liquid has been removed, and the leak has been marked, open the equilization hole by removing the solder. Solder the leak closed using as little solder as possible. A small piece of tape over the equilization hole will allow the hot water test to be preformed. If there are no leaks, remove the tape, and ALLOW THE FLOAT TO COOL COMPLETELY before closing the equilization hole. A final test, and you have 'saved' a valuable float.

Jon