[Cliff R]

Fuel pressure and the Q-jet.

Right to start with anytime you see anyone telling readers a Q-jet can only handle 4-6psi they are simply regurgitating old/outdated information. Same thing with "leaking bottom plugs", or the "fuel bowl is too small"..

Early in the years of production the Q-jet went thru some major design changes and all of them for the better. Most of the rumors we read about come from the very early models.

For example, the leak rate for 1965-1968 units at the rear bottom plugs is right at 100 percent. Crappy design with thin brass cup plugs driven into a casting with not enough material around them. The front plugs weren't much better being not much more than a small piece of lead driven into a hole.

The factory stepped up in 1969 and made the castings thicker and pressed in large/solid aluminum plugs and swaged over them. That pretty much ended the leaky bottom plug issues on the rear of the castings. Shortly after that they started pressing in aluminum front plugs and swaging over them. You still might find a leaker on occasion but post 1974 it's extremely rare and you're not likely to find too many leakers between 1969 and 1974.

Nearly every single person on every Forum in existence or 99.9 percent of anyone who "builds" a Q-jet smears a ton of "monkey chit" over the bottom plugs and also tells anyone reading or trying to learn about these carbs to do the same thing. Do you know how much money I"ve made from folks doing that STOOPID move which in most cases prevents the main casting from effectively sealing the gasket to the baseplate when it's tightened down causing a vacuum leak or ever worse binds the secondary shaft up enough it doesn't fully close and causes a leak there as well.

Second STOOPID move is to install a regulator to keep the fuel pressure under 6 psi. Pressure is volume and even the early carbs with the poorly located hinge pin will take 6 psi without issue IF you use the correct factory float in them, even if you've installed "high flow" N/S assemblies

The later carbs with the relocated hinge pin are fine with much higher pressure with a much smaller float in them. Some "racers" run as high as 10-12 psi with smaller N/S assemblies where others run a little less PSI with larger inlet seats. Pretty much a wash there but I suspect the higher pressure deal simply came from the fact that rebuild kits dating back at least 25 years now did and do NOT come with the .135" seat. Matter of fact most these days are in the .110" to .125 range.

Using the WRONG parts and following POOR advice with fuel pressure is the BEST way I know of to get a nose bleed when you bounce it off the steering wheel at the top of first gear when you suck the bowl dry and the car noses over on a hard run......duh?

I have and continue to try to educate readers on all of these things but sadly it's a constant losing battle as boatloads of old/outdated/inaccurate information floods every Forum on the Internet when it comes to a Quadrajet carburetor.

The article in question here is no different and I suspect that if it were re-written today we'd some some MAJOR changes to it. That assumes the source has learned a few things in the last 30 years or so.

Anyhow I can tell anyone reading this that you do NOT need to thin shafts, grind, sanding roll, hack saw or take a chainsaw to any part of your Q-jet to support big power with it. You just need updated accurate information, the correct parts, and an adequate fuel delivery system for the power level you are using it on. At that point you aren't going to outrun it with anything else no matter how much money you spend or who tells you that you need to go another direction.......FWIW......