Holley carb problem.

[southernspeed]

Hi guys, old and new
Life still goes on over the pond but am in need of the advice from our carb gurus.

My ex wife has a now 3 year old Holley, vac secondaries, elec choke on her '67 Camaro 454. I put this carb on new, tuned it and it's run great since.
She had a running issue recently which resulted in a blow back and wouldn't restart.
Her boyfriend stripped the carb and rebuilt it. Power valve was ok apparently but the secondaries were wide open due to a gummed up actuator rod.
The car starts and runs well but occasionally she'll accelerate gently and the skinny pedal will drop away from under her foot and the tires light up sending her up the road like a bat out of hell. Luckily she's had the foresight to knock it into neutral each time as there's no way those brakes will hold back a tuned 454!!
I've adjusted the throttle linkage and can find no reason as to why it should just go crazy like this, and it's not everytime. Understandably she's kinda nervous of driving it!
Soo.... any thoughts? heard of this before?

 

[kgblazerfive]

Sounds like the new boyfriend is trying to kill her ,

Would guess he did something wrong, like spring on the wrong spot or something or acc. pump in wrong.

 

[ChrisPerry]

Check the motor mounts. If one is broken the motor can lift and pin the throttle. Learned that one on a 67 Pontiac. Once you put it in neutral it will drop to an idle.

 

[Fordum]

If the pedal actually outruns her foot, then something has to move it.
If the return spring broke, gravity might do it, but you would find the broken spring.
If the return spring is being overpowered, there must be another spring, or some kind of actuator somewhere, stronger than it that kicks in under some circumstances.

There are other springs in the carb, but I don't remember any that come close to the return spring in strength.
Plus, something has to trigger it.

I would take a long hard look at anything on that carb that is vacuum or electric powered.
Some of them had a device to hold the throttle open slightly for idle.
It was usually an electric solenoid that was not strong enough to actually open the throttle, but would hold it open after you pushed the pedal with the key on.

The idea was to close the throttle plates completely and choke the engine down when you turn the car off so it would not run-on.

Check for anything that is under power.

Also, the engine mount idea is a real possibility.
I had the same problem in a friend's truck. It was the other mount, and would knock the linkage off when you got in a strain.

 

[southernspeed]

Yeah I went through the motor and trans mount idea as the linkage from the pedal to carb (750 street avenger btw) is the original arm/rod, hence getting the adjustment right is crucial. I know carbs and I know motors but this one is a real 'ghost in the machine'!!