My Willys 3A and 3B Community

TECH FAQ SECTIONS => Engine compartment => Topic started by: SteveK on December 23, 2020, 08:23:55 PM

Title: Carter YF 964S Adjustment questions
Post by: SteveK on December 23, 2020, 08:23:55 PM

Howdy, Jeep Wizards!
I have a '50 CJ3A with a F-head (#648830).  Is there any way to find out the year of this motor?

And, to the point of this Topic: I am rebuilding the carb, it's a YF 964S.  I bought 'master rebuild kits' from both Kaiser-Willys and Mike's, as neither seemed to have all of the correct replacement parts for my carb.

i THINK i am ready to fully reassemble it, but need to adjust the Float open and closed settings.  For closed settings, i have read 5/16", 1/4" and 'parallel with the flat of the top housing (when inverted).  Anyone know which it is?

For open (max drop) setting, i have seen 1 1/4" for 'Early Type' and 1 5/8" for 'Late Type'.  but how the heck do i know which 'Type' i have?

Lastly, i guess i need to check the metering rod adjustment too...still confused about how to do that.

thanks for any advice!  -SK

Title: Re: Carter YF 964S Adjustment questions
Post by: SteveK on December 23, 2020, 08:31:53 PM

This is the best i've found, and it's still pretty vague!
https://www.carburetor-blog.com/knowledge-base/carter-yf-yfa-1-barrel-float/

Title: Re: Carter YF 964S Adjustment questions
Post by: Rus Curtis on December 23, 2020, 08:55:36 PM

SteveK,
The manual shows 5/16' (or the correct gauge to measure with in para F-16. 

I tried rebuilding once about 40 yrs ago.  I had to get it redone. 

Title: Re: Carter YF 964S Adjustment questions
Post by: SteveK on January 01, 2021, 10:02:21 PM

Thanks Rus.  I did set it a "parallel with top" first, installed...and it flooded out the bottom.  There were also other issues with my rebuild of the YF 964S.  So took it back off, took out most of the new parts i put in from the 2 carb rebuild kits i bought (Kaiser-Willys and Mike's Carbs, which seems to tuned to YF 938's) and put back in the old jets, etc.  Reset the float to closer 5/16", and now it seems to be working ok.

Where did you find info on settings for a 964S?  Seems like they were not used on may CJ3Bs, mostly used 938's?  Used on alot of Chevy Stovebolts, sounds like.

Unfortunately i am still having poor power issues, sputtering etc when accelerating.  Will check timing tomorrow and replace the condenser and points.  Then i'm gunna be outta ideas.

Title: Re: Carter YF 964S Adjustment questions
Post by: scoutpilot on January 02, 2021, 06:01:32 AM

The 964S is for the 1950 GMC Stovebolt 216. You need a 938 for the F-head 134. The float setting depends on which needle, Viton or steel-tipped, is installed. Mike's should have included a chart to tell you what the setting should be for the motor. Long story short, the 964 is too much carburetor for your motor.

Title: Re: Carter YF 964S Adjustment questions
Post by: SteveK on January 06, 2021, 05:00:04 PM

thanks scoutpilot.  That is good to know.  I have read that some CJ3B's (F-heads) had YF964S's installed at assembly in-plant.  But perhaps that is not correct.

I will look at acquiring a YF938 (rebuilt, or one to rebuild), or perhaps the "Universal" replacement carb that both Jeepsterman and Kaiser-Willys sell.

Any thoughts on that Universal carb?  Here's the link to it on K-W:

https://www.kaiserwillys.com/new-fully-universal-carburetor-fits-50-71-willys-jeep-with-4-134-f-engine

Title: Re: Carter YF 964S Adjustment questions
Post by: scoutpilot on January 07, 2021, 05:22:19 AM

I'm Old School and partial to original design.