The Stovebolt Site Forums The Shop Area Engine Shop That was an experience - Rochester B gone wrong

Ordered a Rochester B carb from a known rebuilder in Canada and let it set for a year all shrink wrapped in its neat tidy shipping box. Pulled it out today, transferred all the fittings and choke /throttle bracket off the old carb. Went to install it and low and behold it don't fit. Has a larger throttle bore and 1.572" versus 1.500" and the bolt pattern is 2.925" versus 3.000". Well, its sure is a pretty little shelf stuffer. After the fact I noticed the part number C907 was followed by "with R1-B base". Wonder what happens if a guy were to switch the throttle body?

C-907 sounds like a number used by Autoline (Canada). Once upon a time they were a pretty good operation, but I understand things have changed somewhat. That number matches a Rochester B for the 1954 pickup from my notes. Which engine do you have?

Switch the bases and give it a try .

Hey Jon, its the 235, original I think. The engine number stamps corresponds to the 1954 235 as well as the head and block numbers. I think the only think I got accurate on my estimates is the throttle bore. Yep its from Autoline and it looks great! The notes said R1- B base, but of course I had no clue what that meant and their (Rock Auto) vehicle match software showed a match for the 1954 235. Suggestions? Whats your thoughts on switching the base. Different throttle bores for sure.

Not sure what you're measuring.
The flange bolt patterns (between centers) are S.A.E. industry standard, not Rochester or Chevrolet.
Small (216, early 235): 2-11/16" (2.6875"), large (late 235, all 261): 2-15/16" (2.9375").

The 216 throttle bore is 1-1/2" (1.500"), 235 is 1-9/16" (1.5625"), 261 is 1-11/16" (1.6875").

I'm thinking the same as panic.

With a C-to-C of 2.925" (measured) versus 2.9375" (specified), the carburetor flange may fit well enough if the intake studs are not slightly bent or are slightly off center.

The 1.5" or even a 1.572" throttle bore doesn't make sense unless someone took a 216 Rochester B wielded the flange holes closed and re-drilled new ones.

Maybe the carburetor was made the day after a Canadian holiday.

Ronnie, you could certainly swap the throttle bodies and see what happens.

To me it depends on whether the entire carburetor is the wrong one or whether only one part of it was mis-matched. In any case, it is worth a try. At this point you can't return it to Rock Auto nor to Autoline, so what is to lose? The frustrating thing is Rochester produced something like 140 different "B" models, so statistically the likelihood of parts getting mixed up is almost 100%.

Years ago...probably 40 years ago I got an eye-opening look at how one of the largest carburetor rebuilders in the Dallas area at that time operated. Why was I there? They had suffered a fire or two and the insurance company wanted to know if the problem of solvent storage had been fixed. Three things I remember: the speed and monotony at which the assemblers worked (think of something out of a Charles Dickens novel), the fact each person only worked on one model or type that particular shift and the fact all parts had been put in wire baskets by people working as dis-assemblers the day or shift before and soaked in concrete vats. One smaller basket had floats, one had jets, needles, screws, clips, small parts, another larger basket had air horns, float bowls and throttle bodies were in a different larger basket. The place was illuminated by about 3 or 4 fluorescent tubes and there were no windows. The disassemblers worked in more or less an open air area. There was a sign on the front which said "Now Hiring" and it looked as if it had never been removed. So here is how an assembler (we'll call him Charlie) would "rebuild" a carburetor: He'd grab an air horn from one basket, new needles and seats out of a box and float or floats from his another basket plus accelerator pump if that was the style of that model, shake the float to see if he heard anything sloshing around in there and then assemble and measure float levels. He'd set that aside, grab a float bowl, install jets and anything else that went into the bowl. Then he'd grab a gasket from a flat box, some screws and join float bowl and air horn and another gasket and attach the throttle body and connect linkage. Quality control? One guy was walking around drinking a Coke and chewing on a cigar making sure Charlie and the others weren't slacking, joking or talking to each other. Aside from the float/needle & seat I didn't see any other adjustment made at any time. The entire procedure took maybe 3 minutes. So I asked the gentleman I was with "how does he know he matched the original parts?" Answer: "There is no way he could do that and it doesn't matter anyhow. We keep like parts together and we operate on percentages here. We've learned we can mix/match and if there are no cracks or holes in it and all the shafts move, generally the carburetor will work ok as long as we get a new needle and seat and gaskets in there. And if it doesn't, the buyer will take it back to the store and we'll rebuild it again." He added as an afterthought "Mostly people just want it to look good." So there's a glimpse into one "professional rebuilder".

Jon G. - it can be MUCH worse than you indicated.

On certain models, the "rebuilder" will identify ALL vehicles using, say a Carter AFB for a Pontiac. Pontiacs have similar throttle arms on V-8 engines (326, 389, and 421) from 1959 through 1967. The rebuilder would then determine the RICHEST calibration (generally for a 421 with automatic and air conditioning), and any vacuum take-offs that would be necessary for any of the 50 or so different carburetors included in this group.

The disassemblers would disassemble a few hundred of any of the group, grouping parts as you mentioned, and cleaning.

Following cleaning, vacuum tubes would be installed in each casting.

The units would now be assembled with the RICHEST calibration (determined above), and the units would be sold under a single rebuilder's part number.

So a customer goes into a parts house and asks for a rebuilt carb for a 1961 Pontiac 326 with standard transmission " oh, that takes part number 4-607 (or whatever)".

Another customer goes into a parts house and asks for a rebuilt carb for a 1965 Pontiac 421 with automatic and A/C "oh, that takes part number 4-607 (or whatever)".

The listing in the "rebuilders" parts book would be "Pontiac V-8, 1959-1967, all, except SD" - 4-607.

In a different lifetime, when we were still restoring carbs, we used to figure, on average, we could disassemble 10 "cores" of the exact same model, and have enough correct castings to do 6, 7 if we were lucky. Since Carter, and to a somewhat lesser extent, Stromberg, were always our specialties, we have literally thousands of left-over castings (air horns, throttle bodies, venturi clusters, etc.) that we identified and saved.

Jon.

If one is determined to run a B on one’s rig...there are options:

1). Buy from a rebuilder or parts store. I’m sure someone has had a positive experience with this approach. But for the reasons Jon and Jon enumerate, chances of success seem mighty low. And I don’t personally remember anyone posting here bragging about how well their “parts store rebuilt B” runs. Lots of horror stories.

2). Find a B that retains it’s original tag, source the proper kit, and rebuild at home. Much higher chance of success, but the only carbs I’ve come across with tags are NOS ones that are quite spendy. Like more $$$ than I’d pay for a complete, running 235. I suppose if you luck into a good deal or find a tagged candidate still on an engine....this is the best.

3). Rebuild the B you have, or find a cheap/free one and rebuild. There’s a good chance the core you’re working with is already mismatched, warped, or both. But this approach is much cheaper than option 2, with a slightly higher chance of success than option 1. It’s the devil you know vs the devil you don’t.



Overall, I like option 3. The B is simple to rebuild. And there are so darn many of them, that you can do it for very little money. It’s a great platform to learn on and build your confidence. You might even end up with a carb that runs kinda/sorta OK. And when you become dissatisfied enough, you will be more equipped to move onto option 4 and just buy a rebuildable YF.

While it impossible to totally identify a Rochester B carburetor from the casting numbers, we do have a listing of casting numbers which were used on some of the more common Chevrolet Rochester B carburetors. These castings were machined a variety of ways, and therefore castings (with different machining) will be used on different carburetors (some that are not even Chevrolet). In any event, perhaps this list will help:

Tag 7001374 — bowl casting 7002089 — throttle body casting 7002105
Tag 7002050 — bowl casting 7002046 — throttle body casting 7002128
Tag 7002051 — bowl casting 7002046 — throttle body casting 7002128
Tag 7002539 — bowl casting 7002089 — throttle body casting 7002105
Tag 7002540 — bowl casting 7002089 — throttle body casting 7002105
Tag 7003060 — bowl casting 7002046 — throttle body casting 7002128
Tag 7003526 — bowl casting 7003536 — throttle body casting 7003538
Tag 7003863 — bowl casting 7003913 — throttle body casting 7002105
Tag 7003864 — bowl casting 7003912 — throttle body casting 7002128
Tag 7003986 — bowl casting 7004497 — throttle body casting 7002128
Tag 7004039 — bowl casting 7003913 — throttle body casting 7002105
Tag 7004468 — bowl casting 7004497 — throttle body casting 4468
Tag 7004475 — bowl casting 7004516 — throttle body casting 7002105
Tag 7004476 — bowl casting 7004497 — throttle body casting 7002128
Tag 7004478 — bowl casting 7004497 — throttle body casting 4478
Tag 7004495 — bowl casting 7004497 — throttle body casting 7002128
Tag 7004600 — bowl casting 7004516 — throttle body casting 7002105
Tag 7004915 — bowl casting 7004497 — throttle body casting 4915
Tag 7005060 — bowl casting 7004516 — throttle body casting 4620
Tag 7005140 — bowl casting 7005604 — throttle body casting 5140
Tag 7005921 — bowl casting 7003536 — throttle body casting 5921
Tag 7005922 — bowl casting 7003536 — throttle body casting 5922

I do not have data to take the listing newer.

Jon.

Cool!

Handy way to reverse engineer the tag # and/or figure out how mixed up your carb might be. I’m gonna check mine vs that list just for curiosity’s sake.

Panic - you got me, now I don't know what I was measuring either! Here's todays "update" . the bolt center to center is 2.6875 (ish) using calipers measuring outside to outside of the bolt studs and subtracting the OD of the studs ( major diameter of threads is .368" ) , used .375". The bore really is 1.500". So that's 216 CI data and so then I looked up the intake manifold casting number 3835527 and found that its for a 216 motor. That casting number corresponds to a part number 3691933, Group # 3.265 and its application is 1950 - 1953, 216 all. Hmm...and a long exhale. Guess I need to find the correct intake manifold? After all, I have this shiny rebuilt ( although suspect ) carburetor from Autoline. Your thoughts?

[quote=Jon G]Ronnie, you could certainly swap the throttle bodies and see what happens.

To me it depends on whether the entire carburetor is the wrong one or whether only one part of it was mis-matched. In any case, it is worth a try. At this point you can't return it to Rock Auto nor to Autoline, so what is to lose? The frustrating thing is Rochester produced something like 140 different "B" models, so statistically the likelihood of parts getting mixed up is almost 100%.

Years ago...probably 40 years ago I got an eye-opening look at how one of the largest carburetor rebuilders in the Dallas area at that time operated. Why was I there? They had suffered a fire or two and the insurance company wanted to know if the problem of solvent storage had been fixed. Three things I remember: the speed and monotony at which the assemblers worked (think of something out of a Charles Dickens novel), the fact each person only worked on one model or type that particular shift and the fact all parts had been put in wire baskets by people working as dis-assemblers the day or shift before and soaked in concrete vats. One smaller basket had floats, one had jets, needles, screws, clips, small parts, another larger basket had air horns, float bowls and throttle bodies were in a different larger basket. The place was illuminated by about 3 or 4 fluorescent tubes and there were no windows. The disassemblers worked in more or less an open air area. There was a sign on the front which said "Now Hiring" and it looked as if it had never been removed. So here is how an assembler (we'll call him Charlie) would "rebuild" a carburetor: He'd grab an air horn from one basket, new needles and seats out of a box and float or floats from his another basket plus accelerator pump if that was the style of that model, shake the float to see if he heard anything sloshing around in there and then assemble and measure float levels. He'd set that aside, grab a float bowl, install jets and anything else that went into the bowl. Then he'd grab a gasket from a flat box, some screws and join float bowl and air horn and another gasket and attach the throttle body and connect linkage. Quality control? One guy was walking around drinking a Coke and chewing on a cigar making sure Charlie and the others weren't slacking, joking or talking to each other. Aside from the float/needle & seat I didn't see any other adjustment made at any time. The entire procedure took maybe 3 minutes. So I asked the gentleman I was with "how does he know he matched the original parts?" Answer: "There is no way he could do that and it doesn't matter anyhow. We keep like parts together and we operate on percentages here. We've learned we can mix/match and if there are no cracks or holes in it and all the shafts move, generally the carburetor will work ok as long as we get a new needle and seat and gaskets in there. And if it doesn't, the buyer will take it back to the store and we'll rebuild it again." He added as an afterthought "Mostly people just want it to look good." So there's a glimpse into one "professional rebuilder".[/qfuote]

Jon - it turns out to be much worse than expected. The intake manifold casting number is 3835227 which translates to a part number 3691933 and that's shown as used on a 1950-1953, 216 , all. The bore is 1.500 and the studs on the manifold center to center is 2.687. Explains why the holes on the rebuilt carb from AutoLine were farther apart than the studs on the manifold. Panic got me to digging for "usable" information. I have an extra throttle body so I'm thinking its that or go find a good , correct intake manifold. Your thoughts?

Hello fellow Missourian. I've updated my latest "findings" on other replies to Jon and Panic. Short story - I've got a 216" intake manifold. How or why I'll never know. I rebuilt the carb that's on it now. Engine runs, revs, idles nicely but the carb has the typical (?) fuel leak around the throttle plate rod (?). My hope was that the rebuilt unit would solve that problem and the research I'd done seemed to indicate that Autoline had good quality rebuilds. Your thoughts?

Well Ronnie,
You have a 235 carburetor and if you've confirmed you have a 235 engine, I'd just find a 235 manifold. Please check your engine numbers first, however...

If it works, it works. I think there are others here running 216 manifolds on 235s. Pre68 Dave seems to think it works pretty well overall.

Does it leak fuel around the throttle shaft while running? Or only when you’re messing with it while not running? Mine has what seems like an awful seep if you open the throttle with engine off. But the engine seems to suck that fuel right down if the engine is running. Makes sense if I think about it.

If the leak is after you shut off the engine, read the referenced link, and vote in the next election!

Jon.

Fuel leak by throttle shaft

Jon, I used to pride myself on rebuilding to excellent working condition all Model B's. I was only fooling myself because 30 years ago a 235 usually had the original carb. Not so anymore, I sent a thread a few days ago about my 54-3100 carboning up new plugs within a half hour. I rebuilt the carb twice, not a leak anywhere and vacuum perfect. I'm a little afraid to start it up. Using AC-45's, third set. Geeze, I don't know what I'm doing wrong. Ed

JW51 - no it doesn't leak when running , occasionally seeped after setting. It has the thick insulator under it. the top is warped and leaked in the past and that's the issue I'm concerned with. I rebuilt it and it does "work" but I think it might be running rich. I'm going to look for another carb and maybe try swapping the throttle bodies. Sound like I need to go review Carbkings info on compatable Carter carbs.......Thanks for the help.