blue 67 coupe

Just switched over from the 2 barrell setup to a 4 barrell. But now having some problems apparently the carb wasn't in as good of shape as I thought it was. My uncle said that its probably the accelerator pump because when running the car hesitates and acts like its going to die. When you push the pedal a little the car does nothing and sounds like it dies but then takes off and still hesitates. However the slower you accelerate the smoother it is.

He said the part outlined in red needs to be adjusted and it should sit a little lower than it does.


Also when the throttle is opened up all the way when the car is shut off only 2 of the barrells open the other 2 havent moved at all. Could that be a linkage problem?


Any info would help.. monday i'm running to autozone to pick up a rebuild kit and if that doesn't work ill save up for the edelbrock 600.

Also the setup is a holley 600 cfm electric choke on a edelbrock air gap intake.

remicks

That sounds right. I was am about to do the same thing and I'm not 100% sure of the condition of the carb I'm putting on. So I was explained if just starting it falls on its face its the accelerator pump and if going at highway speeds and stomp on it and it falls on its face its the secondaries.

I would just go get the rebuild kit and replace the accelerator pump, its cheap and probably clear things up. What kind of secondaries is the carb, mechanical or vacuum?

Also how well tuned is it? It could be running to rich and when you hit the gas it dumps far too much fuel in and starts to kill it. I had an old truck that would die on heavy acceleration due to a bad tune, got a vacuum gauge, tuned it and cleared it right up.

67mustang302

It's a vacuum secondary, you need to actually be driving the car for the back barrels to open. And at the very least rebuild and clean that thing, it looks a tad crusty. And it does sound like there may be an accel circuit issue, but get it cleaned and rebuilt first, because if you have a clogged main system then the accel pump will act lean, even when it's not.

jonward786

instead of suspecting the carb, i would first question the choice of an air gap for a 2v ---> 4v conversion. an air gap mani on a stock 289 will give u problems...and it does sound like ur running lean.

did u ever pull ur plugs to see whats going on, just to see if ur lean or rich? it would help guide u in the right direction

fakesnakes

That is Holley's least expensive 4 barrel (0-1850). A vacuum secondary with side hung bowls and transfer tubes. It is not a performance carb, but can be tuned to run perfectly. What you have circled is the accelerator pump. While the car is idling, lightly tap the lever and see if the rpm inncreases slightly. If so, you know two things, the pump is working and your idle mixture is too lean. With the car turned off, slowly open the primaries using the throttle linkage at the carb. As soon as you move the linkage, the arm should depress the pump. If not, you need to adjust it so it is just touching, but not depressed at idle.

Norm Peterson

It's possible for the linkage to indicate that the pump is moving, but that doesn't necessarily mean that the pump is actually working. The first check would be to look for two streams of gas being squirted into the primaries as the throttle linkage/lever is moved. Primaries are the barrels that have the choke plate above them - and you might have to hold that open to see what's going on underneath. Motion with no squirts or very weak ones = dead accelerator pump, most likely a cracked/torn diaphragm.

Another possibility (and a little deeper inside) is a bad power valve. PVs can die from a bad backfire, and the history of this carb is not known. But I would not suspect this first, especially if vigorously pumping the throttle does not help keep the engine from stumbling/dying.


Norm

blue 67 coupe

I guess now I just need to know where to get a carb rebuild kit. I tried two autozones today but neither had any and couldn't try O'reilly they were already closed.

Would the rebuild kit also help open up the secondaries because even when driving the car you never feel them open up. Tomorrow I am going to get out there with some carb cleaner and see how much it helps. Then I guess I will go around town and get a rebuild kit and the accelerator pump.

Norm Peterson

Ideally, you should NOT "feel" the secondaries open. If you do, that typically means that there was a momentary bog or slightly lean condition. IOW, that's the "feel" of less power, overall, rather than more. Probably the only way it could possibly be more power is if you're running horribly, horribly rich the rest of the time.

Secondaries opening is not supposed to be at all similar to an automatic tranny downshifting, even though you do tend to get both if you do have an automatic.


Norm

blue 67 coupe

My uncle's 68 you feel the secondaries open and it runs just fine. But i'm not doubting you but I still don't think they are opening. Yesterday on the way back when I got on it it wasn't faster than the 2 barrell that had just been removed. So I was thinking the secondaries don't open causing it to run like a 2 barrell with a 4 barrell intake. But if it has to be running how can I check if they are actually opening if I have to inside the car. Or will they open when its in park and just revved up.

Also does anyone know where to get a accelerator pump for a holley? I went to autozone and they only had the for edelbrock's and they didn't have the right rebuild kit either.
Thanks for all the help so far I am starting to understand more of whats wrong with it.

Norm Peterson

It's possible that your secondaries aren't opening, or aren't opening fully. But that would be a separate issue involving tuning via choosing a secondary diaphragm spring that's appropriate for your car. Too stiff of a spring, such as might be installed on a much larger displacement motor that's not being raced, won't let a small-displacement motor open the secondaries.


Norm