I am considering an Autolite 4100 4-barrel carb with a Clifford intake for use on my 300 six. How well have they worked for you guys? How are the secondaries adjusted (opening)? What would be the best size for a basic stock engine with a 260 cam and EFI headers - street use? Thanks to all of you...jack

 

I've run one of the 480cfm 4100s for a little while and it was fine. It ran too rich, so I need to get some jets to play with to get it dialed in. Other than that it was good.

There's not any way to adjust the secondaries, what you've get is what you've get. The smaller, 1.08" venturi 480cfm, would be best for a 300, although they're getting scarce and can be rather expensive.

 

I've been playing with the 4100 for several years. Concerning the 300, there are a couple of things to consider: If you use the Offy DP intake, your mix screws will be up on your valve cover and hard to adjust. It also makes using the oem filter that screws into the carb impossible to use. But USE the filter as an inline filter. It reduces psi to the carb.

(Read my other thread: Buyer Beware)

Because the carbs are so old and b/c parts are becoming rare, and the price keeps going up, I'm seeing a lot of mixing of parts on epay. That makes it almost impossible to tune the mixed up carbs.

You want the 1.08 venturi, 480 cfm. There is a clock face on the primary bowl, to left of throttle shaft. It will say either 1.12 (600 cfm), or 1.08. Check your base plate for flatness, sand/file if needed. Use .063 primary jets, available through Innerstate Carbs dot com. Kits don't come with the secondary diaphram usually. Submerge your floats for leaks. Replace the synthetic floats. They get lazy.

Check the numbers on the left throttle side toe to determine application. Ford put the 1.08 on big blocks too, just calibrated differently, so know what you are getting. Also, a 40+ year old carb, what are the chances of worn/ vacuum leaking throttle shafts?

Bottom line: I'm sorry to say, but Because they are so old, I'd say pick up a nice late model used Holley or Edelbrock.

There is a Mustang site where you can check the #'s of the 4100. But see, even checking the #'s doesn't assure that the throttle shaft hasn't been changed, or the boosters, etc. It's becoming a crap shoot.

 

I like the Holley 390 CFM , parts are available for tuning , jets ,power valves , secondary diaph. springs, shooters, pumps and cams .

 

[quote=F-250 restorer;12952363]Use .063 primary jets, available through Innerstate Carbs dot com.

F250: I can't find Innerstate Carbs dot com. Can you help? Thanks...jack

 

Interstatecarburetor-- Sorry.

 

[QUOTE=jack orchard;12953545]http://www.allcarbs.com/catlist.php

All State carbs. It had been a while since I looked them up. There is also Mikes carbs, who has quite a few parts for the 4100. But buy the jets from all state. The ones I bought from Mikes were home made.

 

Thanks F-250, jack