The Stovebolt Site Forums The Shop Area Engine Shop Rochester B Choke Bowl/Choke Valve Housing Gasket Holes

Guys, If you have a Rochester B, have you noticed whether your gasket, that sits between the carb's upper section and the middle section, blocks a passageway? I am referring to the choke valve housing ("upper section") aka airhorn, and the choke bowl ("middle section").

In the attached photos https://plus.google.com/photos/117346175748082124087/albums/6042345673177252273 please look at my choke valve housing and choke bowl, and the gasket that belongs between them that I want to replace. When I was ordering my rebuild kit I noticed that my old gasket seems to be missing a hole opening that would match up to a passageway that goes from my choke valve section to my choke bowl section. Please observe, that at the location on the old gasket where one would expect to have that hole, there is only a dark tan "spot" that reasonably suggests some conflict was occurring there during operation of the carburetor. When I discovered this, I simply assumed that the previous owner had used the wrong gasket. I attributed my poor mpg to this fact.

When I was ordering my rebuild kit from Mike at Mike's Carburetors, I did not see among his available gaskets one that would match up to my carb. Nor have I been able to find this gasket elsewhere online. When I inquired, he seemed surprised to see such a hole layout and said he does not have such a gasket. He said I could just punch this hole in the gasket he would send me. (He wondered whether the passageway was not simply a "casting hole" meant to hold a mold together when producing the carb. However, I pointed out to him that the passageway does have an exit orifice in the middle section-choke bowl.)

So I query anyone here as to whether they have run into this issue. Am I likely correct that blocking this passageway would certainly have a detrimental effect on the operation of the carburetor? I am a novice 'mechanic' but it does not seem reasonable to me that a gasket block a passageway. I have the Manual, but the diagrams in it are not clear enough to ascertain the holes in the air horn gasket. As well, I think I have seen just about every online video for the Roch B and I have pored through online discussions about the Roch B, and find no mention made of this issue. Thank you.

I ran into the same thing the first time I rebuilt my carb.The new gasket didn't have the hole so I punched it out. I had to rebuild it a second time and the kit I got that time had the hole in it.I got the second kit from a different vendor than the first.---Jack

Jack, thank you for responding. I was surprised to find the gasket in my carb blocking a passageway, the more so because the previous owner of my truck impressed me as a real hands-on, experienced, kind of guy with these trucks. I, myself, am a novice. I found it so hard to believe my own eyes when I saw the gasket that I even began to wonder whether it was intended as some sort of performance improvement. I spent a lot of time researching online because I was looking to see if there was any empirical or anecdotal evidence to be had in support of blocking that passageway. Of course, there is not. Quite the contrary. My research only confirmed that a carburetor must be maintained precisely as called for by its manual. I sent an email to the previous owner of my carburetor, along with the photos that I posted here, but he has yet to respond.

All in all, if my mpg and starting improves after this rebuild, I will be very happy. Plus, after these several days of research, and doing the rebuild, I feel that I have earned my diploma for Roch B rebuild. I guess that is the name of game with these trucks!

I see you are in Maine. In the very near future, some months, I am moving from Brooklyn to Linneus, which is just south of Houlton. Alden

Several years ago, I posted information about the various gaskets used by Rochester on the B series carbs, and the importance of using the correct rebuilding kit(s). Others posted there was no need to go to a specialty vendor for an expensive kit, as the $11.95 parts house kit had everything needed. Here is some documentation to show differences. All of the gaskets posted are genuine Rochester from my engineering sample files.

This yet another reason why we demand tag numbers when we take kit orders so the correct kit is sent.

Jon.

http://www.thecarburetorshop.com/B_airhorn_1.jpg

http://www.thecarburetorshop.com/B_airhorn_2.jpg

http://www.thecarburetorshop.com/B_airhorn_3.jpg

http://www.thecarburetorshop.com/B_airhorn_4.jpg

http://www.thecarburetorshop.com/B_airhorn_5.jpg

carbking, thank you for responding. If you know of a site that sells genuine Rochester B gaskets, I would certainly order from them next time. I was not looking to save money on my carb kit. I was just looking for the correct parts. In all of my Google searches, no one claimed to have "genuine Rochester B" gaskets. I ordered from Mike because his videos were really good and I felt that he has integrity. He impressed me with the time and attention he gave me and my carburetor on the phone on a Saturday. He looked at photos of my parts, chatted with me, and put together a kit that had everything that needed replacement. All I have to do is use a nice sharp punch and add a hole to a gasket. I have little experience as far as knowing what would be a good price for the Roch B rebuild kit. I spent what I believe to be mere lunch money on my kit from Mike's, i.e., less than I spent when I took the grandkids to McDonald's the other day. He impressed me on several levels. As a novice, I do not want to sound insolent, but I, personally, would not rely on any tag numbers that may still remain on parts of my 50 year old truck when ordering a kit. Photos of the parts seem smarter. Only the Lord knows what someone has done within the part. But that is just me. {Edit: my Roch B had no tag on it. It had a lot of numbers stamped everywhere, none of which came up in Mike's database.}

I have no tag to go by,either,but the kit I got,came with 4 different airhorn gaskets,along with the float gauge,needle valve,"BB"'s,and accelerator pump,(leather). I was fortunate enough to have the correct gasket for my Roch. B included. Only problem with my carb is the "BB" lodged in the discharge tube. Looks like i may have to find another one,but I may have lucked out there,too!

Wetwilly5757, somewhere I picked up that if the wrong size check ball is used, it can get stuck. The remedy entailed drilling some micro-sized hole and pushing the ball out with a stiff wire, then closing up the tiny hole. If you have the manual, the spec for the check ball should be there and then you can check yours with a caliper. I would check, because it is not absurd that even an experienced shop might use the wrong ball when doing a rebuild. As for those tags, it seems that few have survived over the years. Though, as Carbking says, the tags make it easy to know what you have, apparently in years past, guys did not like the appearance and tossed the darn things. Rochester did not help matters much either, imo, by putting id numbers on tags instead of a particular part. On my Roch B, I had a number stamped on every part, yet none of them turned out to be serial numbers or model numbers in several online databases. As well, as you will see from previous posts above, there are Roch B carbs that have a prominent "C" stamped on them which does not indicate the carb to be a Roch BC, the latter a different model with auto/electric choke. A thread on another site said that Rochester made over 140 'variations' of their B carb over the years. Anyway, at least when it comes to gaskets, it is easy enough to make your own. In fact, it is not exceedingly difficult to make most of the parts at home if you have a small lathe and some machinists' skills. Yep, it is a journey. -Alden

Alden - this link to our website will help explain the casting numbers:

http://www.thecarburetorshop.com/Carburetor_ID.htm#IDRochester

Jon.

Jon, thanks. I think I came across that info from previous posts of yours somewhere online. After a few days of meditating over and contemplating my carb (which is laid out across my dining room table, I have come to the conclusion that my Roch B was borne out of two or more donor Roch B's. I am not really bothered much by that fact, since my truck is still....well, my truck. She will not get any awards. A plain Jane. But no less lovable. And Carbking, it takes love. How many times have I considered putting her up for adoption! The other day I held up the air horn section with the float bowl section to good light. Lord have mercy. No gasket in the world could do a proper job of sealing that joint. I have been filing the mating surfaces and I think I have managed to give a gasket a fighting chance. We shall see.

Carbking, do you think that the gas line that goes into the carb should be flared? Single, double, or balloon? And if you do, do you know of a particular adapter to put in that would accept a flared line? I have not had any leaking from it, but I figure if I am already doing such a thorough job on my carb, that I might flare the line. Ignore the fact that the sintered bronze filter will be in place. I intend on moving that filter a little bit away from the carb because I want a pressure gauge between the filter and the carb. I have no better idea to be put on notice of when such a filter is clogging up and coming to the end of its life. And somewhere it got into my head that fuel lines should be flared, like brake lines, without exception. Plus, it is hard on my eyes to look at hose clamps.

By the way, I spent some hours reading postings of yours from over the years. Very informative. Always worth the time. -Alden

{Edit: Jon, just popped into your site. Nice to find a stamp collector here! I have a small 'accumulation' of US. Mostly graded airmails. My dad spent bundles of money on these stamps. But I have been auctioning them away to fund my truck. My kids are not into stamps, nor trucks for that matter. I guess we can suppose what happens to my truck when I go to the happy trucking grounds....}

If the carburetor top has a fuel inlet with pipe threads, then a adapter is needed for a flared line going to pipe thread. All fuel line should have a double flare on both ends. Adapters can be found at most NAPA stores and online. I can not think of any fuel line I have ever seen that didn't use a flared end. My local ACE hardware even carries the flare fitting adapters.

http://hosewarehouse.com/202x2-Male-Connector-Brass?gclid=CKXrsICBp8ACFQmAaQod-IsA7w

This is what you are looking for.

Joe

Joe, thanks for the info. What started as just a cleaning of my carb crept up to a rebuild. I have decided that I am going to eliminate even the slightest possibility of leaks from this Roch B -no matter what it takes. It has become an obsession with me. I have memories from back in the sixties of hearing about engine fires every so often on the morning news traffic reports as my dad drove me to school. Never really understood how they happen, but I wonder whether leaky carbs are the culprits or at least factors of risk. I will also paint my carb. Not only to please my eye, but to be able to note the beginning of a leak. -Alden

Joe, I see that my Roch B's fuel inlet does, indeed, receive a flared fuel line. The previous owner, however, did not use any flare fitting on the line he put into it. I shouldn't be surprised: he also used an incorrect gasket between the airhorn and float bowl (covering a passageway) and he also used an incorrect gasket between the float bowl and the throttle body (covering the pressure release slots on the bottom of the float bowl.) I even have to wonder whether my float bowl is, itself, correct for my airhorn because I have not come upon any published information indicating that Rochester used these vented float bowls on the '66 C10 250 Powerglide. Interestingly, I note upon close inspection that my throttle body's flange casting does not perfectly match my float bowl casting. The mating surfaces each have very slightly different mating gasket beads. Almost imperceptible. Since my carb's tag is missing, and none of the stamped numbers anywhere on my carb suggest a particular model number, I suppose I will not ever know for certain. I know that Rochester had numerous variations of the 'B' for various vehicle models, but I did not know that they varied the carbs within the same vehicle model. That is, I figured all '66 C10 250 Powerglides would have one particular version of the Roch B (7026011 w/idle vent adjustment screw on top of airhorn, per the manual). But I have heard from others with my truck that their Roch B lacks the float bowl slots. So either Chevy put in a version of the carb not acknowledged in the manual or my previous owner has mixed & matched carb sections. Once I get my carb back on the engine, now with its correct gaskets, I hope to be able to "feel" whether my engine is happy with my carb. Fortunately, in the eight months or so that I have my truck, I did not experience any idle or hot-starting issues, nor leaking. I did have poor mpg, but I do not have the level of carburetor knowledge to know whether blocking the slots would cause that. You know, 'they say' that the Roch B is a simple carb to work on. Maybe it is. But that simplicity is well off-set by the tedious task of identifying which simple Roch B one actually has -and what, if anything, a previous owner has done with it.