94 carbs

[Rudolph]

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

 

[Mart]

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.

 

[19Fordy]

51's are the standard issue in Holley carbs.

 

[scicala]

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

 

[Rudolph]

Cool thank you, I will give it a go,

 

[mike42]

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

 

[Rudolph]

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

 

[Mart]

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.

 

[chap52]

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

 

[Rudolph]

Cool thanks I will inspect for air leaks

 

[Rudolph]

No air leaks, should I try the 49 jets?

 

[dorvedahl47pu]

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.