The Stovebolt Site Forums The Shop Area Engine Shop carb question...

i'm glad to see the forum is back online. i have a carb question that's bugging me.
my 53 gmc 228 with a rochester 1bbl eats gas like there's no tomorrow. i took off the carb that i recently rebuilt because i remembered there was a hole in the bottom of it and i wanted to check to see if the new gasket had a corresponding hole in it. it didn't! i assume the correct gasket should have a channel cut into it that would allow the air/fuel to flow from the venturi over to that little hole. is this correct?
i hope so because i cut my own channel. if anyone knows the answer to this or where i might find the answer, i'd sure appreciate it.
thanks much

I don't know the answer to that particular question, but what do your plugs look like? Are they wet? Black? Light brown? Light brown and dry would indicate that the mixture was close. Black or wet would indicate too much fuel going into the engine.

The second question would be is this a 1/2 ton? I have a 1 ton and it had 5.26 gears so it would barely go 45 mph.

Yes you did the right thing cutting a channel in the gasket to the vacuum hole. Read your plugs like Arny said & if it,s running rich take the top off the carb. & check the float level & make shure the power valve plunger goes up & down & opens the ball. These are simple little carbs & work great when you get it right. Check the timing & make shure the vacuum advance is working.

Thanks very much Wrenchbender! I took a gamble and guess right it seems. One thing cutting the channel in the gasket did was make it more cold blooded, so that might translate into better gas mileage. before i didn't need the choke, now i do.

i'll check the carb like you said next although i was very diligent rebuilding it. but being as it was my first rebuild, who knows.

as far as the vacuum, i got it up to 19" and its relatively steady with a jitter of about 1". guess i need to check for a stuck valve sooner or later.

regarding the timing, i seem to get the same reading with the vacuum advance (newly installed by me too) hooked up or unhooked, so i don't really know if it really makes any difference. Even if i get it set between the U|C marks, when i set the idle, its off again! very frustrating. i'm hoping timings not that sensitive.
really appreciate all the help from everyone.
now off to the truck! :-)
tony

Guys - I'd like to jump in here and ask for help but first I will suggest all you Rochester Carb lovers/haters go to www.tocmp.com/manuals/Carbs and there you will find a wealth of Service Bulletins on these and other carbs. Bulletin 9D-8 explains the hole in the bottom of the carb is part of a "vacume operated power System included in the carb to provide additional fuel for sustained high speed driving or increased road load power." The details of how this works is explained in detail. I have run my 235 w/ Rochester BC both plugged (the way I bought it) and unplugged as I rebuilt it and I have never noticed a difference in performance.
Over the last couple of months I have rebuilt and had one professional rebuild done on a Roch. Mdl BC carb with auto choke and I am now 99.9% sure the carb is correct. I can set float levels blindfolded. All parts are new and correct. But, I can't stop the carb from leaking excessivly. On start up it runs dry until the bowl level fills at which point it leaks out the pump plunger lever and if allowed to continue running it will leak out a small vent hole in the top of the carb. This leak "pulses" which is the fuel pump working. Is it possible for the fuel pump to overpower the float and open the needle valve and cause this condition? I obviously don't observe the problem long enough for the truck to explode, I am certain the needle valve is closing properly when the carb is installed on the truck. I appreciate any thoughts on this problem.