I gave a Q-Jet to a friend of mine. He installed it and has stated that it has great throttle responce, but this is what else is going on after he installed it. He said;

i have put the carb on my truck and solved my problem with my old one. yours has great throddle responce and works fine. i have noticed something, when i gradually acclerate, i have no problem. when i put the pettal to the floor from a stop, it will accellerate up to 35-45 and then start to chug, surge. ( acting like your pumping the peddal while your driving) if i ease off the gas and continue it runs fine.
any sugestions?

He also stated that that he double checked all the routing of the vacuum hoses. I told him to check his fuel pump and his fuel filters(he hasn't done this yet). The carb was a remanufactured unit with a 1000 or so miles on it, and sat in my house for six months before I gave it to him. It is now on a stock 350 with cast manifolds and I installed a set of "CV" rods and a "B" hanger before I gave it to him. Any other help or comments would be really appreciated.

 

Fuel starvation. Like you said, filter and/or pump. Other possibilities are kinked fuel line, plugged tank pick-up strainer.

 

It's either what 5-7 said, or it's drowning in fuel because of that "B" hangar. I can't remember the specs on CVs offhand, don't they have REALLY thin power tips?

Tell him to have someone follow and look for black/grey smoke out the tailpipe.

 

The "CV" rods are nearly identical to the "CK" rods so I do not think that this is a problem but it we will look into it.

 

B/CK was way too rich for my manual trans'd ZZ4 camaro. I can't think a stock 350 with iron manifolds in a truck would possibly want that much fuel (my buddy's '71 3/4 ton sure doesn't). The symptoms you are describing is exactly what I had happen with that combo, and I also have the same problem around 35-40mph in my 307 powered riviera (G hangar CH rods). Scan tool on both of them verified rich exhaust, and both have been observed blowing blackish gray smoke out the rear once they reach the "problem" mph.

Whatever it is, the problem seems to show up as the secondaries are starting to REALLY open.

Just for the hell of it, I'd tell him to put in something more like G/CH and see what happens. I mean, it could still be fuel starvation, but the symptoms are so close to what I was having happen it's eerie.

 

We'll have to try it. Thanx.

 

It's what five7 said. You're outrunning your fuel supply. If the filter's not plugged then you fuel pump/lines aren't keeping up.

How to test:

Buy a cheap remote fuel pressure gague kit with a flexible line. "T" it into the fuel line just in front of the carb's fuel inlet. Mount the gague somewhere you can actually see it while driving (temporarily duck taping to the windshield works just dandy). Go make some WOT runs. If you're outrunning the fuel supply it will be OBVIOUS- fuel pressure will nose-dive at the top of every gear.

 

We are steering this direction first. The fuel filter in the carb will be checked and the fuel pump.

If theses are good, then we will try to change the rods and hanger.