Jet size on a 390

[1931flathead]

Here one from the internet looks like this one

[rotorwrench]

There were likely more than 20 different configurations of the 2100 type plus the new reproductions. They are being reproduced for the 60s & 70s cars. If you can find someone that has a set of American wire gauge drills as well as fractional sizes then a person can find the one closest to .054" and carefully see it it fits in the jet. Don't drill it though. It will ruin the jet. They have to be reamed to size if they are modified and that's only assuming that it's smaller than what is required for the FE V8.

[1931flathead]

Jets are cheap I will buy a few different size and try to get it


I'm trying to post pictures of my phone only way I can do it is off a site other wise it will not go through at all

[KULTULZ]

Originally Posted by 1931flathead

Jets are cheap I will buy a few different size and try to get it

Originally Posted by scicala

Maybe just try it the way it is. Good chance it has the original jets, which would get you in the ball park. If lean or rich, then worry about it and increase/decrease the jet size if needed.

Sal

Have you fired the engine yet? It may be the jetting is correct for your application -

Jet Testing

To determine if you have the correct jets in your carburetor, operate your vehicle for 20 minutes at sustained speeds. Stop and pull a plug. Gray - Good, Black - move down one jet size, White - move up one jet size. Do it all over again until you get a gray plug.

This assumes your engine and electrical system is in good running order.

For moving from sea level to over 5,000 ft. reduce your jet size by .002.

SOURCE - https://www.carburetor-parts.com/120-4.html

The jets not having any ID on them makes me suspect as to the quality of the CARB -