which carb is better?

[mustangman65_79]

I don't have any spare money for a new carb, but I do have two 2bbl carbs on hand. I was wondering which one was better and has a bigger cfm. The one that I'm using right now is a stock autolight 2bbl. I also have a stock holley 2bbl. Should I put on the holley for more horsepower? Later on I am going to put on a holler 500cfm 2bbl because I want to use my stock intake manifold. I do have headers and a new open air filter.

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66' Mustang 2bbl 289 coupe, stock.
79' Mustang soon to be a 302-selling-
89' Bronco 351w
AIRMEN FIRST CLASS
KASPAR T. HOWE

[PKRWUD]

Over the years, there were several different 2bbl carbs. What are their part numbers? The Autolite should have a small tag attached to the air horn with one of the screws, and the Holley should have a List number and a pert number stamped on the front, drivers side of the choke tower. Post all of the numbers, and I'll see what I can find out for you.

Take care,
-Chris

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Retired Moderator
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[mustangman65_79]

The tag on the autolite is missing, but I will get the one off of the holley, thanks.

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66' Mustang 2bbl 289 coupe, stock.
79' Mustang soon to be a 302-selling-
89' Bronco 351w
AIRMEN FIRST CLASS
KASPAR T. HOWE

[mustangman65_79]

I straped on the holley, yesterday for fun, got more power, but it ran like crap, I adjusted it, then ran it again, but after a while, it felted like my car was running on 4-6 cylinders, so I put the autolite back on, less power, but no missing.

[Gearhead999]

If you check the Holley you'll probably find that the power valve is blown and is dumping fuel, causing engine to run "fat" and crappy.

[mustangman65_79]

I tried finding the power valve, but I don't know what it looks like, I have an idea, but I didn't see anything. I know about holley's and their powervalve porblem and I do belive it to be the problem, because right after i put it on, it back-fired. If u know where it is, please tell me.

[Gearhead999]

You take off the float bowl and the plate that hold the two jets. The power valve is screwed in that plate from the carb side. If you want to be certain that the valve is blown. When you take the carb off the engine don't tilt it and dump all the fuel out. Keep the carb upright and drain and remove the fuel bowl. The fuel will drain out when you take a bottom screw out of the bowl. [four screws hold bowl on] Then pry the jet plate off. When you see the cavity that the power valve fits in to, look for fuel here. If you have fuel there the valve is blown. Plus, if you have gone this far you might as well change it anyway. Good starting, normal run of the mill power valve is a 6.5. Get new gaskets too. They are a pain to scrape but someone has to do it.

Put back together and run it. Bet it runs better. You shouldn't let it backfire if at all possible. That's what ruins power valves.

They make a little pop off valve kit that you can install in you carb to HELP protect the powervalve from backfire. The kit is REAL CHEAP and easy to install. Check it out while you have carb off car.

Happy Thanksgiving, let me know if you need help.

[mustangman65_79]

Well, if I didn't have to work this whole week, I'd do it right now, but the first day I get off, I will try it out, thanks for your help.