My car is a 65 with a 289 and C-4 trans. It was an original 2 barrel carb, but it has a 4 barrel carb on it now. I have no idea what brand of carb is on the car, because it unfortunately has no markings on it. But I do have a picture.



The carb has one large problem and I think it is the vacuum secondaries causing it. Anywhere from a dead stop to around 10 mph, if I give the car any more than half throttle, the gas pedal actually floors itself. It does not let up until the car shifts into second or I shut the ignition off. This occasionally is a problem.

I originally thought it was a sticking throttle, so I put an extra spring on the throttle return linkage.



But that didn't help. I think my problem is that the vacuum secondaries are opening too aggressively and actually overriding the throttle linkage and flooring the car. Yes, the pedal goes all the way to the floor. Here is a pic of the secondaries.



This the carb that came on the car when I bought it a couple of years ago. I did not remove any of the linkage. Any suggestions?

 

Putting an extra spring on the return is like putting used tires on top of a redneck trailer house to keep wind from rattling the top. Take your carburetor off and rebuild it. It looks like it is in need of a rebuild anyway. All the gum and crap that has built up on all the connections and hinges need to get cleaned off anyway.

 

I can't rebuild it if I can't figure out what brand or model of carb it is.

 

looks like an autolight 4100 to me.



I think your car is haunted personally, I can not think of a single reason even if your secondaries were being forces open when it would cause your pedal to move...they 2 are not connected....hence 'vacuum secondaries'

Have you tried changing where your throttle return spring is located? Perhaps move so it is not so close it to the throttle arm of the carb itself. (just a thought...here is a completely different carb and linkage setup just to illustrate what I mean by moving the spring

 

Thanks! I'll get the rebuild kit tomorrow at the store.

 

It's an Autolite/Motorcraft 4100.

 

Before you spend the money on a rebuild kit you might want to check these two things. First, disconnect the secondary linkage and see if the pedal still floors itself. If it does, it's not the secondaries. Second, your carburetor has a mechanical linkage rod connecting it to the gas pedal. A broken motor mount on the drivers side could cause the condition you describe. Set the brake, chock the wheels and "power brake" the car while someone watches the motor with the hood up. Be prepared to turn the key off if it starts to floor itself. If the motor lifts, the mount is broken and iscausing your pedal to floor as it pulls on the linkage rod. My money is onthe broken mount.

 

You were right about the engine mount. The mount looks correct when you look at with the hood open, but when you put the car on the lift, you can see the that the engine is sagging about 1 inch on the left hand side. I need to rebuild the carb anyway because doesn't work very good besides the runaway throttle. I hope to fix it next week when I am back from a trip and I have the parts. This is the job that kept me occupied today:



That is what is left of the turbo in my rx7. I found the black part down the exhaust pipe.

 

+1 for occasionally

 

I was going to suggest the engine mount, because somebody had this problem before on the forum. The engine will shift, and pull on the rod, causing the carb to open.