71 idles fine. After warm up it stalls at light

[stevef22]

HI Everyone!!! So glad to be here! Im in heaven!! lol


I have a 71 Auto all stock, matching numbers Vette. The carb looks like a QJett (Four barrels). I can take pictures and attach.

She starts up fine... Idles fine... Left idling for 30 mins... Runs fine while idling. She is idling at 6k

The problem happens when I drive. lol


I start driving... After about 2-3 miles. I am finding myself having to press more on the gas to get the same power. Im driving 30-50mph through the neighborhood.

When I slow down to take a turn I notice the idle is at 5k... ( idle is lowering after warm up), And I am still applying a little more gas to get the same power.

After about 4mi the she wont stay on at a stop light. The idle is about 2-3k... then she stalls.


The only way to get her to turn back on is step on the gas to the floor and crank that ignition!!! Then she starts to come back to life... slowly.... spewing black smoke out both tailpipes and gassing out the person behind me....

Then I must throw her into drive and take off!!! (before I stall again, I need to keep those RPM high enough and cant slow down or she will stall again. ).... Tires peel out a little, the person being me must think... "JERK WITH VETTE!!!" otfl


What is going on here? I need the vette gurus to come to the rescue!!


Also, importiant to note. While driving, if I step on the gas, the engine and exhaust make this bogging down sound. She actually does not accelerate, just makes a bogging down sound. If I slightly release the petal... then she takes off.


Please help me out here. Going to take her to buddy mechanic soon and would appreciate multiple ideas. Thank you very much!!!

 

[Kevo]

Sounds like a carb problem, or possible stale fuel is car sits a lot. Carb overhaul is likely.

 

[GTR1999]

Old Q-jet issue was the accelerator pumps. When worn and even some on the market today, they will cause a bog when pressing on the gas. My old Buick was real bad when I was a kid, floor it and BLAH nothing, then it would catch up and go.

Lars is the guy to speak to about building it and where to get the good parts. Once properly setup they are a really good carb.

 

[stephen]

not a guru

the only problem i have found and can comment on this about is maybe the car was timed while cold and not at a driving rpm. first time i timed my car i didnt bring the idle up to to 2000 and it ran like crap.

 

[TimAT]

Check the primary wire from the distributor to the coil, make sure the breaker plate is well grounded inside the distributor. Every time the ignition advances the breaker plate moves and can break those connections. Past that, it's back to the carb.

 

[vigman]

The OL leaky Q jet trick

There are aluminum staked plugs in bottom of the carb that tie into the fuel system...
After all this time they leak.... and when heat is applied they leak WORSE which explains your symptoms.

http://www.highperformancepontiac.com/tech/hppp_1107_home_remedy_quadrajet_carburetor/

Rochester drilled several passageways through the Quadrajet casting during the

manufacturing process​

​

. Aluminum, brass, or lead plugs, depending upon the year and location, were used to seal the main body’s external holes and prevent outward leaks. The plugs located on the bottom of the casting, directly beneath the primary and secondary metering jets, are most susceptible to leaks.
On a Quadrajet, the small plugs (left) located directly beneath the primary metering jets

As the Quadrajet evolved over the years, it saw refinements, including new plug types and retention methods, which improved its performance and reliability. While some bottom plugs remain leak-free today, particularly in later castings produced during the ’80s, a lifetime of

heating and​

​

cooling cycles, and the resultant expansion and contraction of the dissimilar metals used in early castings, have compromised the plugs’ effectiveness in preventing fuel leaks.


Read more: http://www.highperformancepontiac.com/tech/hppp_1107_home_remedy_quadrajet_carburetor/#ixzz2vznP4eY1

 

[bill81vette]

Welcome to CAC!!
enjoy!!!!
I would try to contact Lars...sounds like a carb that needs to be rebuilt...
good luck!!!!

 

[Vettehead Mikey]

The OP hasn't been here since Jan 22.