All Small Six Carter RBS jet/needle sizes

[Mookie]

Greetings, I have a '73 Mustang with the 250ci I6. The EGR rusted away years ago, and the previous owner 'tuned' the carb to compensate for the lean condition. But that only adjusts the idle mixture, not the running mixture. Making it rich at idle and pretty lean under load.

Because the carb is running lean without the EGR gasses. Is there anybody who has replaced the main jet and needle to richen the mixture back to a healthy ratio?

Thanks.

 

[wsa111]

You need to run an A/F ration test with a wideband tester. Cruising is 14.5-14.9, WOT 12.2-12.5 with Ethanol fuel. Without Ethanol 12.8-13.1.
Carter jets are normally measured in thousands.

 

[chad]

"...replaced the main jet...to..."
no jetting available. the RBS's are pressed in. what U got is what U get. made for the 250/4.1.
make the carb the way it wuz engineered (fix egr) so as 2B oem spec (actually the whole system).
Tune ign 1st to rule it out then go onto carb.

 

[comet6]

I have a reman carb, and another what I believe is original 73 carb. They have different well jet sizes and step up rod diameters. If you need to go richer, measure what you have and calculate the needed area increase by percentage. Drill and test.

 

[John Ha]

I guess I'm curious to know how you know it's too lean under load?

 

[comet6]

Just to clarify. The removable jet is the well jet. there is an idle tube below it. Swapping that jet probably influences idle and transition. The power enrichment circuit has a pressed in jet. The step up rod is what you need to cure lean condition under load. If op will measure those, message me and I will tell you the sizes I have for reference. I can find no specification listed.

 

[John Ha]

Just noticed that this was originally posted 2 years ago :-\

 

[chad]

and yet interest goes on & on & on &...