any carburater guys here?

[SIXBANGR]

1 barrel on my '63 Chevy pu. Rebuilt it yesterday. Tried to set it up today with a vacuum gauge. I can turn the a/f screw all the way in with no change. The carb and engine are from a late 70's GM car, 250ci.

 

[Little6pack]

This may sound far fetched but I remember me and Pronto putting a rebuilt carb on his sisters 70 malibu. We dicked with it for 3 hours trying to get it to run proper.

In the end the gearhead neigbor came over and told us you have to adjust the timing. We did and it ran perfect.. Maybe that will help

 

[novaderrik]

the throttle blades are probably open too far, and it is running on the main circuit. when this happens, the idle mixture screws do nothing.
set the timing to the proper spec and hook the vacuum advance up to a full manifold vacuum source.
baseline the idle mixture screws- 1.5 turns out is a good starting point.
if it's an auto trans put it in drive and tune for most vacuum at the lowest idle speed it will maintain with the throttle blades closed as far as you can get them.

 

[alwayscode390]

Good Stuff ^^^ ---

 

[novaderrik]

oh, yeah, io forgot one thing- make sure the engine is warmed up and that the choke is all the way open before even attempting to tune the carb.

 

[SIXBANGR]

tried this morning, warm and choke open. The timing should be at 8-12 depending what this 250 inliner is in. It is at 25-30. I tried resetting it but it won't stay running. The trottle blade is open , I looked last night. If I drop the idle at all to try to close it,it won't run either. I just went threw the 1 barrel because it floods. After, I sprayed around the carb with carb cleaner and it revs up just about every where i spray. Just bought the old truck 2 weeks ago. Bad carb or timing gears?

 

[Rebel]

If you have the mixture screws in the whole way, you are drawing air in somewhere you aren't supposed to, think vacuum leak. Intake gasket, brake booster, p.c.v., vacuum advance diaphragm, vacuum hose....If you can't find it, you may have internal carb cracks or air going around the throttle shaft. Did you match up your gaskets (overlay and hold new and old gaskets up to lighy, EVERY hole needs to match perfectly)? Sometimes in the aftermarket the gaskets aren't made properly and the ports are either blocked or allowed to vent to atmosphere. As already discussed, timing and dwell will do the same thing. Did your damper pulley slip? Take your vacuum gauge on a manifold vacuum source. Base vacuum should be 15+, advance distributor to max. available vacuum. Should be 20+, if not, you have other problems. If it is 20+, back distributor 2" vacuum and timing wll be very close. Hope this helps. Just double checked your post, if it was flooding, either the needle and seat were dirty or worn, the float was heavy (brass: had a hole in it, or nitrophyl black absorbed fuel) or the choke wasn't coming off. Also, did you soak the carb in solvent? That's were your throttle shaft problems start. It will wear from years of use but was blocked by years of crud you just cleaned off.

 

[Scott Atk]

As stated, make sure there is no vacuum leaks. If there isnt, you can drill a very small hole in the throttle blade. That will allow you to close off the blade enough to get it off the main metering circuit and back on the idle circuit.