Carburetor Issues

I have just completed my engine rebuild with my son on his 76 Maverick. We put a small 260 lift cam, dual exhaust manifolds, rebuild head, and recurved the distributor as well as a nice dual exhaust system on on the car. The car sounds Great! Didn’t know the little 250 engine could sound that good! I am having some big issues with the little single barrel carb. I am getting gas smoke from the exhaust and the carb will not adjust. The idle will not turn down and the air/gas mixture screw doesn’t seem to do the trick.

Since this Will be a daily driver for my son I was thinking of getting a new carb and stop fighting with this old one. Can anyone guide me in this should I upgrade to a double barrel carb? Can they be directly mounted? And which one should I get?

Or should I just get a new single barrel carb? If so can anyone recommend a really good one?

Hi, there are a couple of things to figure out. There are not to many carbs you can't make better, good , or perfect. It just takes working on it. First, the ignition tuneup has to be on the money. If the timing is off, cap, rotor, wires, plugs, etc. are in poor shape you will never have any luck with the carb. The carb setup is last.
When someone can't get the idle down or adjust the idle mixture screw I think two things. Vacuum leak(s) and high idle cam.
My best way to adjust a carb is on a cold engine, look at the way the choke closes, and opens as the engine warms up. You might have a choke pulloff. That could be a vacuum leak right there. then when the engine is warmed up the choke should be fully open and held open by spring pressure.Now the high idle cam should be disengaged. and the idle should adjust from the idle adustment screw or solenoid. After the idle is good you slowly turn in the idle mixture screw until the engine stumbles, then back it out @ 1/2 turn or so.
I think your engine has a lot of emissions spaghetti and I wouldn't be surprised if there was a vacuum leak connected to that.
Personally I would get it running as good as possible before buying a new carb, but I did the 2 barrel conversion on my 200 and it is really great.
Good luck

2X ^^^Mr. B Ron above^^^. Carb is further dwn the list from ignition. ID what U have, learn/do a tune there, move to carb nxt. Make sure the SCV/LOM (U've been here 10 posts so I assume U got this) match (carb/dizzy feedback system)...
U did the valve seals at the X of other wrk, no? (not 'guides').
the choke opens fully @ the 5 - 7 min mark of running?

Thanks BRon and Chad. I have the timing spot on. And the head was completely reworked. This carb is the original and the car has set a long time
I have not looked for leaks and will start from there. I have adjusted the carb the way B RON suggested but to no avail. I really am leaning toward the two barrel carb. I will break this carb apart and give it a good cleaning and go thru the steps of setting it again and see what happens!

Thanks!

If that carb sat unused for a long time then it will likey have varnish in the fuel bowl and small passages so yes do clean it really good with some Barrymans spray carb cleaner throughout then install a new carb kit, plus a new float and it will likely work great again. Your 1976 250 Maverick would of had a Carter YFA stock it's a very good carb and is also perfectly matched to the stock DuraSpark II ignistion system your 76 Maverick also has. Good luck

A suitable 2Bbl carb through a suitable adapter is fine for moderate performance improvement. Depending on the specific Carburetor and the setup, it can improve gas mileage and performance or cause terrible mileage and performance loss .

Suitable 2Bbls are often a big improvement from the early Holley 1bbl's and the Weber (Holley/Weber) PROGRESSIVE 2Bbl can offer improved mileage, better performance and a consistent idle (something early 1bbls often lack).

'been running a H/W 5200 (W32/36 clone) thru $15 2X1 adapter on the '63 170 for @ 15 years with no problems...

. . .


Unless engine is heavily modified , over optimistic large CFM carbs may work somewhat, but run eye-watering rich and experience throttle-bog from inadequate venturi vacuum .
. .




have fun

... isn't "carburetor' French for "Don't F&%k with it" ?

Howdy Back Maholmes and All:

I'm guessing the one barrel carb you're working with is a Holley #1946. Is that correct? My limited experience with them has not been good. They are one of FoMoCos first efforts at cleaning up these engine as per EPA. They are encumbered with thermal, vacuum other feed back systems envolving hoses, sensors and wires making for a mind blowing puzzle. I would use it only if you want to have a stock appearing engine.

There are several good one barrel replacement options. The first one barrel for the first 250 engines is the Carter RBS, '69 to '73(or so). It is low profile, simple carb with few tuning options. Next would be a Carter YF (early) or YFA. These were the second, stock carb to come on 250 engines and used until the Holley 1946 appeared. The YFs are fairly tuner friendly.

The two barrel option is best for your 250, but requires some additional work. You could use an adapter but that raises other problems, like hood clearance. The 2 into 1 adapters are bolt-on and relatively easy DIY. THe best way is to modify the carb mount on the intake log. Many on this forum have done this mod.

On carb, two choices, a two stage two barrel like Webers (many clones). They require critical tuning and are relatively expensive. The other option is a wide based two barrel like the Holley 2300 and the Autolite 2100. Both are easily tunable, relatively inexpensive and easily available. These would be my first choice for a street 250.

I hope that helps. Let us know what you decide.

Adios, David