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Old 06-12-2021, 04:09 AM   #1
Rudolph
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Default 94 carbs

I have this 94 Holly carb on my engine, I used it as it was in good condition, put a kit in it and used it for a few years but not sure if it has the right jets? It has 51 stamped on the jets but most of the 239” motors I have had 49 stamped on the jets, is that a big jump in size?

I have changed the engine for a fresh rebuild, old engine was worn so not sure if the plugs were black from being rich or oil soot, but it wasn’t ridiculously rich
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Old 06-12-2021, 06:29 AM   #2
Mart
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Default Re: 94 carbs

I think 51s are one of the stock sizes so should be ok. 49s might be a bit lean. Maybe good for higher altitudes (If I have that the right way around.)
50s or 51s are normally the ticket.
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Old 06-12-2021, 09:00 AM   #3
19Fordy
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Default Re: 94 carbs

51's are the standard issue in Holley carbs.
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Old 06-12-2021, 11:02 AM   #4
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Default Re: 94 carbs

The jet sizes varied on later ones in the mid 50's and on trucks. I've seen some in my Holley manual as high as #56, but for your era carb #51 sounds good for sea level to 5,000 foot elevation.

Yes Mart, you had it correct. The higher the elevation, the smaller the jet.

Sal

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Old 06-14-2021, 02:48 AM   #5
Rudolph
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Default Re: 94 carbs

Cool thank you, I will give it a go,
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Old 06-14-2021, 04:42 AM   #6
mike42
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Default Re: 94 carbs

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Rud……I just took an original 1940 94 carb apart and the jets were .50

This carb as far as I know had never been reworked per the original owner.

Mike
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Old 06-22-2021, 09:24 PM   #7
Rudolph
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Default Re: 94 carbs

I have run the new engine and it seams a bit rich, plugs have black soot on them but insulator wasn’t totally black, I had a hunt though the box of carbs I have and they all seem to have 49 jets in them
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Old 06-23-2021, 03:08 AM   #8
Mart
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Default Re: 94 carbs

Rudi. Check the flatness of the bottom of the carb body and the top of the base. If not flat it can cause a vacuum leak which will stop the power valve from closing and cause a rich condition. You'd think a vac leak would cause lean running but it's the opposite in this case.
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Old 06-23-2021, 06:37 AM   #9
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Default Re: 94 carbs

To check for that leak as Mart suggested. With it running use an unlit propane torch to blow propane around the base of the carb. If engine speed increases there is a leak. You can also use carb cleaner but that can leave a stain or mess up paint. Chap
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Old 06-23-2021, 03:11 PM   #10
Rudolph
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Default Re: 94 carbs

Cool thanks I will inspect for air leaks
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Old 06-24-2021, 03:17 PM   #11
Rudolph
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Default Re: 94 carbs

No air leaks, should I try the 49 jets?
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Old 06-24-2021, 05:03 PM   #12
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Default Re: 94 carbs

For what it is worth, I had an issue with my 40 tonner not wanting to idle with the choke fully open. I was going insane trying to fix it. I checked for vacuum leaks, installed new choke linkages, took the carb apart and cleaned everything again (I had previously put a kit into it), and adjusted just about everything I could with no improvement. Then I took a big swing and simultaneously installed a new power valve, installed 49 power jets (I knew the truck was from lower elevation and I live at about 4200 feet), and adjusted my float. Works like a champ now. Personally, I think the float adjustment is what did the trick. It was dropping much too low. I'm sure the jets and power valve helped as well though. Good luck.
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