The Stovebolt Site Forums The Shop Area Engine Shop Linkage Question: Changing from Rochester B to Zenith 228

Hello Stovebolt Team
I'm in the process of seeing what all would be involved in switching from my Rochester B to a Zenith 228 on my 261 engine in my 1953 1/2 ton. Fuel line modification is not an issue if its needed, I just hope there is no major linkage adjustment that is needed. Anyone have any experience with this? I don't actually have the Zenith yet, it is in the mail.

Hey Patrick,

Great carburetor. The linkage is the easy part. This idea could be a cost issue.

Previous posts (923835 and 1143215):

https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/924835/Searchpage/1/Main/136777/Words/"what+year+did+the"/Search/true/what-year-did-the-carb-bolt-pattern-change-do-zeniths-fit-235s.html#Post924835

https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/1143215/Searchpage/1/Main/168248/Words/"zenith+carb+specifications"/Search/true/zenith-carb-specifications.html#Post1143215

In the first posting, Carbking says the size 3 Zenith for a GMC 270 is excellent for a slightly to moderately modified 261. Notice the statement of +/- 3% (donor and donee). It's not a direct swap for a stock 261. My words here, a size 3 may run a little lean on a stock 261 engine. Maybe bore it out a little and change the cam to get more CFM.

If you want to buy (they can be $$$) a Zenith, make sure you do your homework and get the right one. Unfortunately parts can easily be swapped with another carburetor. You need to verify that the parts inside (removable venturi, jet etc.) are correct to the spec-sheet and the round brass ID tag riveted on the top. GMC used different carburetors for the same 270 engine. Small truck versus big truck.

228BV11
228 - series
B - throttle and choke shafts crossed (the other option is A - throttle and choke shafts parallel)
V - vacuum operated power jet valve
11 - size 11 (SAE 2) (2 11/16 c-to-c)
GMC 270 engine 100, 150, 250
As an example: ID tag 11693 (1956 GMC) Venturi #33, main jet #31, power jet #20, well vent #16

228BV12
228 - see above
B - see above
V - see above
12 - size 12 (SAE 3) (2 15/16 c-to-c)
GMC 270 engine 350, 370, 400
As an example: ID tag 11965 (1956 GMC) Venturi #34, main jet #33, power jet #18, well vent #15

+++++++++

Normally I wouldn't cross post like this but the 261 is an odd bird. Carbking informed us that there are suitable Carter YF models (after 1962) that can be made to work on a 261.
My words here....the issues are the linkage (throttle opens opposite direction) and vacuum advance port (below the throttle valve) on some models.

Previous post (81523):
https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/81523/Searchpage/1/Main/12295/Words/"Carb+King%2C+a+little"/Search/true/carb-king-a-little-help.html#Post81523

It would probably be best to post this (Carter YF on 261) as a new topic for any future discussion.

Thank you for your reply. I found a Zenith 228 228BV11 for $50, good rebuild able and complete condition, was in contact with carbking twice on the phone yesterday, and he said it would be a great carb for my stock-built 261. I verified the numbers as well on the dime-size tab on the top of the carb (11963). I will pull up the links that you posted and read more, thanks for your attention.