'66 Mustang 2bbl jetting - Ford Mustang Forum
 
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post #1 of 6 (permalink) Old 11-16-2017 Thread Starter
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Thumbs up '66 Mustang 2bbl jetting

Hi all,

Got a 1966, 289, with 2bbl carb. I think the carb is off a 390 2bbl Mustang. Not my choice of carb, but that is the way it came and the car runs good.

It has been jetted for operation at 5,000 feet - Loveland CO, using # 51 jets.

I've got the car in Phoenix, around 900 feet altitude.

Any educated (or other wise) guesses as to what jet I should be using at the Phoenix altitude?

Thanks for your help, Dave


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post #2 of 6 (permalink) Old 11-16-2017
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Quote:
Originally Posted by 1carguy View Post
Hi all,

Got a 1966, 289, with 2bbl carb. I think the carb is off a 390 2bbl Mustang. Not my choice of carb, but that is the way it came and the car runs good.

It has been jetted for operation at 5,000 feet - Loveland CO, using # 51 jets.

I've got the car in Phoenix, around 900 feet altitude.

Any educated (or other wise) guesses as to what jet I should be using at the Phoenix altitude?

Thanks for your help, Dave
Check the carb for a part number and mention any engine mods. I believe ivygt is the man with you carb jetting related info.

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post #3 of 6 (permalink) Old 11-16-2017 Thread Starter
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Autolite 2 bbl carb - 2100. Rebuilt stock 289 - no engine mods.

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post #4 of 6 (permalink) Old 11-16-2017
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Autolite 2 bbl carb - 2100. Rebuilt stock 289 - no engine mods.
There are a few different venturi sizes in the 2100.
0.98 = 24.9mm/24.9mm = 190 CFM*
1.01 = 25.6mm/25.6mm = 240 CFM*
1.02 = 25.9mm/25.9mm = 245 CFM*
1.08 = 27.4mm/27.4mm = 287 CFM*
1.14 = 29.0mm/29.0mm = 300 CFM*
1.21 = 30.7mm/30.7mm = 351 CFM*
1.23 = 31.2mm/31.2mm = 356 CFM*
1.33 = 33.8mm/33.8mm = 424 CFM
The 390 probably had a 1.33. Have checked you plugs? The color can help to identify a rich or lean condition.

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post #5 of 6 (permalink) Old 11-17-2017 Thread Starter
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At 5,000 feet plugs look good, using #51 jet.

After looking on line I found that for every 2,000 feet of altitude, the jet size should be changed 1 or 2 sizes. I've come down 4,000 feet so I will try a 53 or 54 jet, THEN look at the plugs.

I'm done, over & out

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post #6 of 6 (permalink) Old 11-17-2017
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There were at least a dozen different 2100s used on 390s as stock carbs. The kind of 2100 number needed is something like C6MF-D which was used in '66 full-sized Ford 390s. The different carb numbers used a variety of different boosters which make a big difference.

Not knowing any of those details the jets installed were anything from 50 to 60 for a 390. Its hard to know how those work on a 289 without trying them. But since you say 51s were OK at 5,000' then I agree your 53 is about right at 900.

The real formula for changing jet sizes is the 1/4 power of the relative air densities at the two altitudes; that is the square root of the square root. In millibar the 'standard' density ratio for 900' vs 5,000' is 980.7/843.1 = 1.163 Take the square root of that twice and you get 1.0385 times 51 = 52.97

I would start out with the 53. The absolute best jet for any day also depends upon the barometric pressure and temperature.
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