The Stovebolt Site Forums The Shop Area Engine Shop New Tech Tip - 2 Parter!! Rochester B-Series Carburetor

The venerable Rochester B-Series carburetor. Thousands of them still soldier on atop Stovebolt 6's around the World. Are they unrebuildable?? Heck NO! Jon G has put a lot of time and work into this 2-part Tech Tip that will make you a Rochester Rebuilding pro in no time! A must read/must have for any 'Bolter with a B-Series Rochester!

Thanks Jon!!!

Part 1 - Common Issues covers a lot of ground with a helpful schematic on the last page.
Part 2 - Casting Fixes looks specifically at repairing warped Air Horn and Fuel Bowl castings, with helpful details and images.

Check them out!!

Jon G. - VERY NICE!

Since you commented on the orifice size of the fuel valve seat, I thought maybe I could help. I pulled the prints on B's from 216, 230, early 235, mid 235, late 235, early 261, late 261, and 292 CID Chevrolet engines.

In all of these carburetors, Rochester supplied only 3 different fuel valves: 7002359, 30-1, 7023801.

And the orifice sizes are (drum roll):

7002359 - 0.082 inch
30-1 - 0.082 inch
7023801 - 0.082 inch

It does appear that at least Rochester wanted the fuel valve seat orifice to be 0.082 inch!

The other Jon.

Thanks very much for the compliment and the information, Jon. Very nice to know Rochester wanted .082" but whoever made the generic kits must not have had that information. I think (emphasize the word "think") the smallest of the 3 probably was .082", but the other 2 I found in those carburetors definitely weren't. The one marked "big daddy" took my breath away.

They had the information, they just made a "One size fits none" kit so they didn't have to make 100 different versions for make and model specific engines.

And a HUGE thanks to "carbking" for offering us, to help publicize the new Tech Tip, a holiday discount just for Stovebolters on select Rochester Carburetor Rebuild kits!!

Check out the details in the Swap Meet!

Thanks Jon!!!

Regards,
Jo(h)n

I’ve got one side higher than the other. My thought is work the high side down while watching that the low side stays constant.

Just wondering if you agree.

Also attached a picture of my jig. 3/8”x5”x5”. Used all thread then bolted in place with a nut on top and bottom and a lock washer.

I think I over did it. So I build another jig. Do you think I can pull this side down 0.004” at a time? Baking at 400 deg in between?

You did, Darren. The good news is you can undo that...unless you really overdo things and crack the metal you can work it back/forth as needed. Try putting something like a piece of metal between the nuts/bolts and move the corners back down...004" at a time. Slow, easy steps.

It’d be really cool if we eventually get some “testimonials” from folks who rehabbed their B with the tech tip and a carbking rebuild kit. Such as…how did it run before vs after, fuel mileage before and after, etc.

I’d be willing to try it myself, but recently liquidated all the B’s I had sitting around.

John added the Rochester BC Service Manual that carbking provided to the Engine Tech Tip (third attachment). It's in PDF format and only 14 pages. Image below is only the cover. Go to that Tech Tip to get the document.

I believe I have the carburetor halves straight. That was an amazing journey. Over correct and then re-correct. Again all happening at 0.004” at a time. Now I need some help where the fuel comes in. I think I am leaking from the brass fitting that fits into the carburetor so the fuel line can attach. I originally had some thread sealant on those threads, but many have said that is not proper. As I think you should be able to see in the pictures the gasoline is on the top ridge of the top half of the carburetor. So what are my options?

The housing has a 1/8 in. tapered pipe thread. The fitting should not bottom out like that. Either the threads in the housing &/or fitting are wore down. Try a new fitting.

George

Darren:
I had the same issue. I put a copper washer on the fitting - seems to help.

Is this the correct fitting? How would a copper washer help?

With pipe threads, if they're not tight enough, they'll leak thru the threads. A copper washer might help seal it, but the threads might be more prone to strip out, as they wouldn't be fully engaged. A new fitting like George suggested would be the first thing to do. It's possible the threads in the housing are expanded too much to fit correctly even with a new fitting. Another thing to try would be additional wraps of teflon tape, being very careful not to get any over the end of the fitting.

I use Permatex Seal Lock on fuel line fittings when necessary.

https://www.amazon.com/Permatex-575...HPee-ipgXdhlYkVocbixInxO9LhoCYI8QAvD_BwE

I found a new fitting and it is certainly snugger but still leaks. I had previously used the Permatex listed above, but was also getting a lot of feedback on not using either the thread sealant or teflon tape. But now it seems I’m back to thread sealant. Thank you to everyone that has been commenting in such a timely manner. I’ll let you know how it goes next weekend as I’m out of time today

John, after the airhorn and bowl have been straightened, have you given any thought on what to do if the fuel line connection on the airhorn is worn and the fitting is leaking from that point? Is there room to re-thread to a bigger diameter and use a larger fitting? I started down this path wondering if a helicoil might be the solution so you see where I am going with this. Thank you for all the great input.

Years ago on a Rochester BC I had this problem and it occurred on a Sunday afternoon, Darren. I had to drive to work Monday so I simply cleaned everything well, mixed some JB Weld, coated the threads lightly, screwed it in and then coated the entire area around that fitting (on the Rochester body). It was all set the next morning and for almost 20 years it never leaked again. I stopped using it and swapped for a Carter but I suspect it would not leak today if I still had it.

I closed the final gap. Modified the procedure slightly. I used a couple of C-clamps because I was afraid of asking the threads on the bowl to do two much. I have everything fitting together perfectly. But now I have a problem with the threads. The back passenger side threads on the bowl gave out. Striped! Is there enough material to tap this for a larger thread screw? If so, what size? Thank you.

Man! that sucks. At this point you have nothing to lose by re-threading it if no other means is available. I wonder if a Helicoil would work?

If it can't be re-tapped maybe a through-bolt and nut would work or maybe a threaded rod with nuts on each end.

I think a helicoil would be the correct solution. I've used them as small as a #10 machine screw. Way stronger than even tapping for a larger bolt.

Worlds rarest Helicoil, #12-28. It’s just never easy!

I think you can order them from Advance Auto, etc. as well.

https://www.hdchasen.com/number-12-28-helical-threaded-inserts

Otto, what about the drill size, tap and insert tool? That were I hung up at now. That’s where I’m stuck. I need a complete kit. And the cheapest can find it for is $37 plus $15 shipping. Thank you.

See what Advance Auto has. Usually if you order online you'll get a discount - sometimes 20%. They don't charge for shipping over $35 or you can pick it up in the store.

I did mention using JB Weld to solve this same problem years ago, didn't I? JB Weld is resistant to gasoline...even ethanol laced gas. 7 years ago I mixed some and thinned it with acetone enough that I could paint the inside of the gas tank on a log splitter. Still working just fine. JB Weld now even makes one type designed just for gasoline. One important thing to remember is you ideally should have no more than 4 psi on the high side as far as fuel pressure goes. Any way you go, good luck!

You did mention JB Weld for the fuel connector. I’m actually thinking about going to a metric M5 Helicoil. I’m thinking it is actually a slightly smaller screw so I’ll need to remove less material for the insert.