Edelbrock accelerator pump

[410 John]

I took my 1406 edelbrock apart to clean it out. Is the accelerator pump usually real hard to press down? I probably still have something clogged. It idles but stumbles when I try to drive it. Or it’s the accelerator pump?

 

[ChuckN]

Shouldn’t be hard to press down at all. It is spring loaded, but if it feels like something is binding, maybe take it back apart and reassess.

 

[410 John]

Thanks. It’s coming apart again, for sure.

 

[75gmck25]

Sounds like there is a problem with the accelerator pump.

For a part throttle stumble you also might want to try different step-up springs. Edelbrock has a kit with springs rated at 4-8” of vacuum, and I think a stock 1406 spring is a 5”.

The spring’s vacuum rating determines when the carb rods go from cruise to power mode as the vacuum drops. A higher rated spring (e.g. 7”) will make it go rich (rods to power mode) sooner as you press the throttle and the vacuum drops. This often gets rid of a part throttle bog.

 

[410 John]

I had time and worked on the truck yesterday. Opened the carb back up. The accelerator pump is squirting. I blew carb cleaner through all the jets. Put the carb back on and once full of fuel it starts right up, but still has the stumble. This thing ran fine before, until the carb clogged. It sometimes will rev past the stumble but the next rev it’s there. Usually with a pop out the exhaust afterwards. I never moved the timing, but did a cap, rotor and HP coil while the carb was off. It’s either something I did or the carb still has a clogged circuit somewhere. I have zero time and haven’t driven the truck since last fall. But I would drive it a lot if it was working.

 

[fast 99]

Put the old coil back in and does it have the strap ground? I know people are trying to improve their vehicle, but the quality of parts today is sometimes questionable. On top of that a stock HEI coil can usually produce twice the KV necessary for combustion.

 

[410 John]

I’ll give it a try.

 

[410 John]

Just found some time and switched the ignition back to the old stuff. No change. It was getting a little dark, so I took a flashlight and looked down the carb and the accelerator pump nozzles are not squirting. Bench testing previously, the squirted. Not sure what’s up.

 

[ChuckN]

I know you’ve had it apart, but have you gone through and actually rebuilt it with all new gaskets and give it a good cleaning? And when you had it apart, did you happen to change the accelerator pump rubber?

My remembrance might be off, but I think under the accelerator pump nozzle there are check balls, something might be hanging up too.

Never mind my bad memory, if you haven’t gone through the complete rebuild process, Hagerty has a two part video on YouTube that I put on an iPad while I rebuilt mine on a card table in the garage.

 

[410 John]

It will come back off when I get the time.

 

[410 John]

Got to work on the truck today. This carb needs zippers. Had it out two more times. Found the main issue. Under the needle and seats(there’s 2) are mess filters. One was clogged almost solid. The other almost as bad. I also took the distributor out and put it back on TDC for number one. Took it to get gas and it ran, but sputtered here and there. Filled the tank and it’s leaking from probably the sending unit. It’s not leaking in the driveway right now. I found my timing light and it was way advance. But I’m having issues seeing the timing mark. I’m going to get some white paint. Also, the starter never sounded good and is acting up with the timing changes.

 

[Ricko1966]

I didn't read everything,but if I had a stumble that I didn't have,before, accelerator pump working. I'd be looking real hard at my transition circuits. The transition circuit is just barely above the throttle plates and is to deliver fuel just as the throttle plates open,and they will cause a stumble like an accelerator pump. Lots of people crank the throttle stop screw in too far trying to make their cars idle and end up with a stumble because they are using their transition fuel to idle. I put that part in there for anyone who is using their transition fuel to idle. Found you a couple of pics of transfer slots,I always called it transition circuit. Anyway the pics will show you what I'm talking about if that circuit isn't clear it can cause a very annoying stumble.

 

[410 John]

I think I have a 305 balancer on my 350. It’s not under the pointer. So it’s hard to see with the timing light. Plus the mark is probably off.

 

[1lejohn]

I think I have a 305 balancer on my 350. It’s not under the pointer. So it’s hard to see with the timing light. Plus the mark is probably off.

Some of the old trucks didn't have the timing tab that mounts to the timing cover. They had a small sight that you looked down through in the water pump mounting area. It's located between the back of the pump and the block. Many of them are missing. Just throwing that out there, my truck was like that the tab didn't make sense.

 

[squaredeal91]

I think I have a 305 balancer on my 350. It’s not under the pointer. So it’s hard to see with the timing light. Plus the mark is probably off.

If you find true TDC you can make your own line. I've done that before so I can see what the timing is at. I usually time by ear till it runs the best without a ping.