New Carb

[Buford]

New Carb surges then stalls. It's a direct replacement Q-jet on my '74 350 auto. The old carb was beat, wouldn't start unless primed and couldn't rev up at all. This one will rev up but it always stalls after the choke valve opens up (almost immediately). I'm guessing it's the timing but I can't find the timing collar on the front anywhere. Anyone go through this before?:confused ;help

 

[1BAD80]

If it only run's when choked that mean's it's not getting the gas it need's to keep running.
Check your filter and gas pump or a large air leak.

 

[Buford]

I will check the filter, but this only happens at idle not when I'm giving it some gas. I sort of have to pump it a bit to keep it going.

 

[1BAD80]

Old Post :
This one will rev up but it always stalls after the choke valve opens up (almost immediately)

New post:
but this only happens at idle not when I'm giving it some gas. I sort of have to pump it a bit to keep it going.

Is the choke open or not?
When shut off is there gas running down on the inside?
Some dirt could be in the main jet's if it only run's when pumped.

 

[Buford]

I'll try again, after I put the new carb on I actually am outside the car watching the carb with breather off, it will always start but it immediately opens the choke wide and surges to a very high idle followed by a stumble then stall.:confused

 

[1BAD80]

I still think it's one of these three.
If it only run's when choked that mean's it's not getting the gas it need's to keep running.
Check your filter and gas pump or a large air leak.
Do you have to keep pumping it to keep running after the choke is opened?
Then I would check out the main jets system.
Here's a site for your carb.
Maybe you can find something there.

http://www.recarbco.com/technical/

 

[Buford]

Yes I have to keep pumping it to keep running after the choke is opened, thanks for the link.

 

[1BAD80]

Sound's like a low float level, or a plugged main jet.
The pump pick's up from the bottom of the float chamber.

 

[Buford]

Hey 1Bad80 the link you gave me pushes me towards a big vacuum leak but I couldn't find it. So I put the old one back on for now but it really runs rich, it's 30 years old. The thing is on the old one is if I pull a vacuum hose it idles up quite a bit, so one is running too lean the other too rich.:confused

 

[1BAD80]

Check the rear throttle blade's to see if their shut all the way.
If their open the slightest it will give you the problem as described. Push down while running on the rear of the butterflies with a thin screwdriver very easy, if it changes thats your problem. I just fixed one with the same problem.

 

[Buford]

I'll put it back on tommorow and give it a shot -- thanks.

 

[1BAD80]

Here's another good site for Rochester carbs with manual and trouble guide.
If the carb's off you should be able to see light thru it if it's open.
http://www.recarbco.com/technical/

 

[Buford]

Got it working good now, the gaskets are identical for both carbs but I though the vacuum leak had to be coming from the base since I plugged everything else, so when I put the new carb back on I used the old gasket and now it works very good. Though just knocking around the new one on the bench may have dislodged a bur or dirt I'll take it the way it works now. Thanks for the help. :dance

 

[1BAD80]

Look at the old gaskets and see if you can see where the leak was or if the inside was touching the throttle blades. It would be good to know what the problem was just in case. Great to hear thats its running good.

 

[igasper10]

I'm guessing it's the timing but I can't find the timing collar on the front anywhere. Anyone go through this before?:confused ;help

From the posts it seems like you've solved your problem, but as far as timing...

I have a 74' 350 as well. Its a project car, so I had to do some major wire brushing to find the timing collar notches and be able to read them. Its on the driver's side. You should have a direct line of sight just in front of the alternator. If I remember correctly the timing for L48 350 is 8 degrees BTDC.

Ian

 

[Buford]

Timing

Yes that is the right timing, but mine is actually transplanted from a '78 L82, and it has HEI and a few other non '74 items, so it's a bit of a challenge with plugs and everything else, but it does run strong now. Still just guessing at the timing till I get it to a pro.