I ahve a 390 with a year old rebuilt by HOlley two barrel carb. Whenever I step on the gas the secondaries spray out gas like they are supposed to but then they stop. Aren't the4y supposed to continue to spray out gas as long as you have your foot on the peddle? The engine has all new ignition parts and the fuel pump checks out fine so I have narrowed the problem down to the carb. Whenever you step on the gas it just won't move, it wants to stop. It does not backfire or sputter, it is just being deprived of gas. So, my question is, aren't the secondaries supposed to continue to spray gas as long as you have your foot on the gas peddle? If so, what is the part that is supposed to keep the secondaries spraying the gas? I don't think it is the little pump that sits on the side of the carb that initially sprays the gas because it has no problem giving off that first squirt. I am at a loss; does anyone have any ideas?
thanks for all the help you guys always give me
brad

 

The squirt you see is just the accelerator pump and only sprays when the throttle is being depressed. The main discharge is under the venturi and you most likely can't see it.
I am very opinionated on this but there is no such thing as an over the counter remanufactured carb that is worth bringing home. They are almost always junk, PERIOD. I had one from
holley on my 300- 6 and I am sure I did a lot more rebuilding to make it work that they ever did at their facility.
Just go find one from a junkyard and go through it yourself. They are about the simplest carb ever made. Just make sure you get one that has the original tag. It will be a metal tag with the numbers and it should be on the front under one of the screws that hold the top on.
Or just buy a new 2 barrel holley, that is pretty much a bolt on.

 

I wish I has known that rebuilt carbs were junk before I bought this one. I rebuilt the original one for my truck but then traded it in for the rebuilt because i did not see an improvement. I know that the accelerator pump is supposed to spray when you press the throtle, but is it supposed to continue to spray as long as you depress the throtle even if you have it down for a while?
thanks for the info
brad

 

The spray only continues for as long as the throttle is in motion.
It's purpose is to supplement the fuel flow until the latentcy in the venturi's fuel delivery is overcome.

 

Right, the venturis' use the air velocity to "draw" fuel into the carb bores; the accelerator pump is designed to provide fuel in the mean time so there is no lag in the engine. Basically all the throttle does is open the throttle plates so more air can pass through. In contrast, the choke prevents air flow so the engine vacuum pulls fuel into the motor to aid in starting.

 

Think of the accelerator pump as a little ballon with water in it. You mash it flat and the water comes out. Now you have to refill it. The pump works the same way.

 

Just my opinion, but I'd scrap the Holley and throw an Edelbrock on there. And just as a side note, I found this really cool site the other day to calculate needed carburetor CFM based on max engine rpm and displacement, try this:
http://www.csgnetwork.com/cfmcalc.html

 

I would too but Seifferlein is dealing with a two barrel and to my knowledge edelbrock doesn't make one.

 

On my 1972 Ranger XLT it still had the original 360 with the original 2 barrel carb. The factory carb had been rebuilt 2 times already so it think it had enough. I went and bought another Motorcraft remanufactured carb from advance auto and stuck it on the truck and it runs perfect. Its probably been on the truck now for over a year.

 

William if you have a Motorcraft store, you are very fortunate. I used to get all the important parts for my pickup from their warehouse in Anchorage and then they pulled out and some crappy parts took their place. I haven't seen motorcraft parts since, out side the Ford store. They were not connected to Ford dealerships. They were an aftermarket parts warehouse that retailed through local independant parts stores. I always had good luck with their parts. And AC Delco also had a fair line of reman parts if you were working on a GM.
The problem with most parts houses we created ourselves by always price shopping so we just keep getting cheaper junk like the ever popular Reli-on line.

 

oops, I didn't read close enough to see it was a 2bbl. But I think at one time I saw an Edelbrock 2bbl, but it could just be my decayed memory. Anyway, I would forget the 2bbl all together and throw an intake on for a four barrel. Should be able to get a stock one pretty cheap, as long as you don't have to pay for shipping by weight!! haha. First thing I did to my truck was put on a four barrel intake and Edelbrock carb, and it was worth it.

 

Wow, thanks for the info guys. I rebuilt the carb my self and at first it did not seem to run any better. Now it seems to run somewhat better. However, just for fun, I pulled off the drivers side muffler to run it on a straight pipe. I have done this recently a few times but this time it was making a funny noise. It sounded similiar to the pufffing noise that an exhaust leak makes, but this time it was coming out of the tailpipe. I do have exhaust leaks but I ahve had them for a long time and have never heard this noise before While running straight pipes. Do you think it could be a small backfire from a bad exhaust valve? Would a compression text determine if I have a bad valve?
thanks
brad

 

If you have a pop sound under deceleration, your idle mixture may be a bit lean. I'm not certain of this since it's been a while since I monkeyed with carbs, but that is where I'd start.

If you want to check valves, then do a compression test or cylinder leakage test.

 

A poping during deceleration may indicate that the point gap is too narrow. If you suspect a valve just hook up a vacuum guage. If the needle is vibrating or dipping quickly and sharply you may have valve problems. These guages are inexpensive and one of the best diagnostic tools you can own. Get one that has an instruction sheet. A dipping or sweeping needle is usually carburation and a generally low reading is timing or a just plain tired engine. If it starts normal and begins to drop or drops bad when you bring up the rpms you may have a restricted exhaust.

 

I have never had any luck with a rebuilt carb either. I suggest going with a 4 bbl as well. I have a 390 and what a huge difference it made when I switched from a Motorcraft 2bbl to a Edlebrock performer 4bbl. I have a Holley 650 vacuum secondary. I am going to get an Edlebrock in the near future as I am not too thrilled with the holley. Jegs has great deals on carbs.