wondering what the main jet size is supposed to be on a rochester B, running it on a 1954 235 engine. currently has a jet in it stamped "57". the jet that was in it before was a 59 and it ran extremely rich. im asking because it runs leaner but the plugs are still getting relatively black. any links to places i could pick up some different main jet sizes?
Last edited by Mr. Dane; 12/15/20202:59 AM.
Owner of the most temperamental 1951 3100 in existence
Getting parts for a Rochester from Jon is about as likely as finding a chicken with lips! He's a Carter guy, as are most of us with a lot of years' experience making stovebolts run right. Chances are, the main jet isn't your problem- - - -it's a sticky power valve that stays open most, or all of the time and bypasses the main jet. Polish the power piston with a felt buffing wheel and some jewelers' rouge, and do the same thing to the bore it rides in, using a wool gun cleaning mop that is a snug fit in the housing. Then check the top of the carburetor for warp- - - -they're notorious for opening up a vacuum passageway and leaking enough vacuum to let the power valve open up too soon. "The ABC's of fuel systems- - - -Always Buy Carter!" Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jon offers a major rebuilding kit, which includes the correct main metering jet, the correct vacuum piston spring, and other non-normally found parts for all of the Rochester type B carburetors; assuming the customer has the tag number. Basically, if one does not have the tag number on the Rochester B, one has a door-stop. And then suggests that if you want better performance to switch to a Carter.
Shucks Jerry, I even make kits for Holleys
Mr. Dane - Jerry is probably correct about the power valve being open all of the time. It could be a sticking piston, or the infamous warped carburetor body that is a trademark of the Rochester B. With today's fuel, a carburetor with original calibration THAT IS FUNCTIONING NORMALLY, is much more likely to be lean rather than rich. Changing main jets to a leaner calibration is generally not the answer for the Rochester B.
Suggested superior alternatives: Carter, Stromberg, Zenith, or if one has the hood removed, a 15-year old lad standing on the running board pouring gas into the engine from a leaky boot!
Jon.
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
Basically, if one does not have the tag number on the Rochester B, one has a door-stop.
Not that Iām advocating Rochester B carbs but some of the carb bases are stamped with the model as was mine.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ā59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
Take the headache out of trying to make a Rochester B work. Carter's replacement carburetor for that time period: Carter YF 966s 1950-52 235 but will work decently on your 54 Carter YF2100S 1950-56 235
I posted a 966S link in the "ebay and craigslist" section that sold for $18.25 + shipping.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
I can replace my model B with a Carter. Probably have to change/modify gas line, vacuum line, throttle linkage, choke linkage, air cleaner. Plus cost and hassle to buy and ship "new" carb from (possibly unreliable) eBay seller. The "new" carb would probably have to be rebuilt.
Or I can simply put a kit in my existing model B.
I can imagine which option would give me the headache!
To each their own, however, we have found that if one uses the list I have posted previously on this forum for WHICH YF to use for WHICH Chevrolet engine BY YEAR and displacement, your list is reduced to:
(A) bending the fuel line approximately 1/2 inch (B) the cost and hassle of buying and shipping a carb from a (probably unreliable) ebay seller or possibly a more reliable different source.
One other issue you didn't list, is that most ebay vendors do NOT provide a mounting gasket, or if they do, it is incorrect. The mounting gasket suggested by Carter differs from the Chevrolet mounting gasket, BUT FOR BEST RESULTS, SHOULD BE USED!
Carter engineered the carbs to basically be "bolt-on" swaps provided one acquires the one Carter suggested for the application. The only exception of which I know is that Carter decided everyone needed automatic chokes for 1957 and newer engines. Of course, if one purchased a new carburetor from Carter, the correct mounting gasket came in the box with the carburetor.
Your residing in Canada provides an additional stumbling block if the vendor is located in the USA. Shipping to Canada has always been difficult, but right now during the pandemic, almost impossible. This is probably the best argument for currently retaining your Rochester B. (or maybe find an ebay vendor in Canada). We were shipping to Canada before the pandemic, even though our losses from both carriers and Canadian customs still exceeds our gross sales to Canada (was hoping to finally change the balance) but simply had to give up during the pandemic.
Jon
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
Suggested superior alternatives: Carter, Stromberg, Zenith, or if one has the hood removed, a 15-year old lad standing on the running board pouring gas into the engine from a leaky boot!
I'd be willing to try Door #4, if I could just find a 15-year old kid willing to do that. Fortunately, my engine has a Carter already installed.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Jon I know shipping to Canada can be a problem, especially for those of us who live in rural areas - UPS doesn't deliver here. USPS works - got a package from MI yesterday - a week early. Ordering stuff through Amazon seems much better than eBay.
The only problem (at the moment) with my carb is that it's a 7015013 which is designed for a 261 and I have a 235. Seems to run OK, but I don't do a lot of highway driving.
Yes you have to be careful ordering .I have been discouraged after ordering a few years ago only to loose out no parts ,no money back.Ordered recently Canadian dollar is low shipping is high and duties are being added .Had a vendor forget to add a 5.00 part was great sent it out right away cost another 20.00 in duty . My experience is it is about double by the time you get what you ordered.
judging by all the back and fourth, i think ill stay with the rochester. its a great carb other than the run rich condition. im also going to a hotter plug, ill see if that improves it, it could fix it for all i know. if all else fails ill rebuild it and polish the power piston. it moves freely but that was when i had it off the truck and apart. thanks everyone for all the information! it goes a heck of a long way!
Owner of the most temperamental 1951 3100 in existence
on a side note, im not doubting the superiority of the carters, they definitely have a better design and are arguably more common, but to me its just like holley vs edelbrock. ive already spent too much on carb parts, so ill make do with what i have.
Owner of the most temperamental 1951 3100 in existence
I know I am probably being silly here and I apologize if I am, but I assume you have adjusted the idle mixture screw in or out as the case may be to obtain best lean idle?
on a side note, im not doubting the superiority of the carters, they definitely have a better design and are arguably more common, but to me its just like holley vs edelbrock. ive already spent too much on carb parts, so ill make do with what i have.
I think you should at least do as Jerry suggests and check the operation of the power piston. It's a common issue.
I'd be willing to try Door #4, if I could just find a 15-year old kid willing to do that. 
