Inliners International Forums General Discussion Engines 292 w/Rochester Model B and BC Questions

Hey Guys, You all helped me out so much earlier that I thought I'd give it another try. Well I finally got my 292 running well and now I'm in the middle of a long checklist of "tweaks" and among most of them is the carb setup. I have an Offy 3X1 manifold with one Rochester Model BC (cable choke) model as the primary and two Rochester Model B (no choke) carbs as the secondaries. They have all been meticuliously rebuilt but I'm encountering a somewhat strange anomoly. I can turn in all the idle screws and it will still run! I checked for a vaccum leak using the propane bottle method and it didn't change the idle speed at all. I even removed the 3X1 setup this past weekend and tested each carb individually on the stock manifold (I had some time on my hands). It turns out that the center (BC Model) is the culprit. Is there something that I should be looking for other than the idle and the bowl vent adjustments that may require attention? It seems pretty strange that it will run this way. Also, I'm getting a bit of fuel seeping at the gasket where the air horn and the bowl assembly are attached even though the float level is set exactly according to the book. (by the way, should I have used some sealant there instead of "High Tack" along with the gasket) I've been told that the Motor's Truck Repair Manual's float level settings are a starting point and that you can only get the floats set correctly while they are on the truck. Is this correct? Any help is greatly appreciated. Here's some pics of the completed engine:
http://pedaldoctor.com/images/Finished_292_Engine.JPG
http://pedaldoctor.com/images/Finished_292_Engine2.JPG

when you set the floats did you have the carbs sitting like they do on the intake? on that what looks like a slite angle? And just a 2cent note you may want to pull those end pins and install studs so you don't end up with a exhaust leak.

The problem may be a poor seal on the vacuum circuit controlling the power valve. Check this page for more information:

Rochester type B\'s used in multiples

If the power valve is open, it can effect the idle.

Jon.

Thanks Larry, Actually I set the floats during the carb assembly/rebuild. According to the instructions, you need to measure them in relation to the surface of the inverted air horn. Also, you're absolutely right, I should have replaced the pins on the head with studs when I did all of the other ones. I realized that once I had already set the engine in. I'm pulling the head off in a couple of months and I'll do it then. Thanks for keeping me inline! (pardon the pun) :p -Tim "Doc"

Thanks for the post Jon, I've read some of your advice in reguards to carburation on other posts and was kind of hoping that I could flush out a response from you! I'm going to pull the carb off on Thursday and check out the seal on the power valve. It's a fresh rebuild but anything can happen right? Also, I have a collection of spare B series Rochesters that I can pull from just in case. Thanks as well for the link, I had found (and lost) that link earlier this year and I've been trying to find it again. Thanks for your help. What would you suggest that I do to eliminate the fuel seeping at the seam? It's minimal but it buggs me to no end! Is there a gasket sealant or even a better quality gasket that I should use? Should I set the floats so that there is less fuel in the bowl? I was told from a local shop that a high float will also cause the engine to idle fast. Is it possible that excess fuel in the bowl can runoff into the air horn somehow? Thanks again for your help. -Tim "Doc"

The fuel seeping from the seam is caused either by the warpage, or some misguided individuals attempt to fix the warpage by filing, and removed the sealing ridge. If you straighten the castings you will stop the leak, at least for a couple of years.

Jon.

Thanks Jon. I have checked and the sealing ridge hasn't been filed (shudder) but I'll have to check to see if there's any warpage. What's the best way to straighten the castings? It seems that they usually will leak at the same point on these carbs. Usually on the front side. Thanks again Jon, -Tim "Doc"

Tim. I have 3 Roch. that came off of an Offy. I got some years back. I don't know what kind of shape they are in. I never used them. I run the 5200 on my setup. If you need parts, you are welcome to them. I think I have a progressive linkage for the Offy. as well. I am located up in Macon Co. about 75 miles NE of you. I run a built 292 in a pulling tractor.

Tim - the casting straightening procedure is covered in the article.

Jon.

Thanks Jon, I saw that right after I sent the reply. I'm going to try that this weekend.

PedalDoctor:
Since nobody has said it yet, that is one sweet looking engine and truck project! I am sure this all will work out just fine for you.

jb


;

Thanks for the offer Hud, I'd love to have a trio of Rochesters for spare parts. I'm new to this, how do I get in contact with you? -Tim

Thanks again Jon, I spent the weekend working on the carbs and the casings were warped. Not severely, but enough to be a pain to correct. I built a jig out of 3/8" steel and some "C" clamps and it worked quite well. It is a VERY long process like the article says and I'm hoping that they will hold their shape for some time after this. It took about three hours PER CARB so it's best to have another side project to do when your doing this. It also turned out that the center carb's power valve was hanging up so I dressed it out and cleaned it up and now it's working correctly. I'm going to build up a couple of spare carbs to have on hand. They shouldn't warp on the shelf should they? I was thinking about leaving the screws that fasten the two halves of the casings slightly loose and then torquing them down right before I need to use them. What do you think?

Thanks again Jon,
-Tim

Tim - I don't know if they will warp on the shelf or not. I would suggest assembling, but applying NO torque to the top screws. Also, if your memory resembles mine, an attached cardboard tag suggesting screw tightening before use. :rolleyes:

On the carbs you use, figure about 3 years before you have warpage problems again.

And you might consider the ABC's of carburetion for future projects:


(A)lways (B)uy (C)arter

Jon.