I have been battling multiple issues with the '51 Olds 88A that I purchased last fall! When I bought it, I knew that it had an over fueling issue by the black smoke coming out of the exhaust and the black soot on the rear bumper. I figured that it would need an adjustment or at the worst, the carb would need rebuilding. After trying to adjust the carb, turning the idle screws made no difference, and that I had already replaced the plugs, wires and checked the timing but all of this had made no difference I took the carb, a Rochester BB, off and had it professionally rebuilt. Now, I have used this guy for a number of years, he specializes in carburetors and knows his stuff. He does a thorough job, not just a clean and throw in a gasket kit type of rebuild. At the time that I picked it back up, he said that he found that someone had been messing with it and put in part of a gasket kit and had replaced the carburetor base, with a new one, and that he found a lot of dirt in it. After cleaning and installing a new rebuild kit in it and checking it over for worn shafts and such, it checked out good and was ready to go! I put the rebuilt carb back on, at initial start-up it seemed to run good but not long afterwards it went right back to missing and blowing out black smoke. I called the rebuilder and told him the problems I was having, I also mentioned that someone had recently replaced the fuel pump. Because it is a 100 mile round trip to his shop, he suggested that I check the fuel pressure first. Turns out that it had about 8 pounds of pressure at the carb so I installed a inline fuel regulator ( a Mr. Gasket cheapie) but while adjusting the pressure the starter hung up and came apart! This is getting pretty long winded so I'm not going to go into all the starter problems that ensued, eventually I got the starter issues straightened out and the car actually seemed to run pretty good for awhile but once again it started over fueling and, now, it wouldn't start at all. At this point, I had had enough! I didn't touch it for quite awhile! Fast forward to a few weeks ago, because of all the electrical issues that I had been having, I converted the 6 volt system over to 12 volt. Now, back to the fuel problems, I replaced the fuel regulator and got it to start. It ran but it barely ran! It wouldn't idle, puked out gobs of black smoke and when I tried to accelerate, it would miss and backfire. Still suspecting a problem with the fuel pump, I hooked up a gravity fed tank and low and behold it started up and ran pretty good. It still had a noticeable miss at idle that seems to go away when accelerating and still has a bit of black smoke coming out of the pipes. So now the question ( bet you thought that I would never get here), is it the fuel pump or is it the carburetor? Turning the idle adjustment screws still doesn't seem to make any difference. Or could I have a problem with both the fuel pump and the carb? Anybody got any suggestions or idea's? Thanks...[/QUOTE]
How long did it run good?..just minutes or an hour, or a week? Did the idle mixture screws work good when you put the carb back on? First thought is that "a lot of dirt" means the gas tank is suspect. second thought is that ignition issues can mimic carb issues. if it was mine, I'd see if the carb has more dirt in it first. If it's clean as new, then I'd be checking ignition .
Gotta look at the whole system, clean the tank, blow out the lines, put a filter in, go through the carburetor again, adjust per spec
Three thoughts: (1) An engine with a "perfect" (there was NEVER such a thing as a perfect Rochester BB, thankfully obsoleted after a single year) carburetor and a defective ignition system will run RICH and blow black smoke. (2) The el cheapo dial type regulators regulate pressure by regulating volume. Often, regulating the pressure sufficiently low will cut the volume to where the engine will not run. (3) A very wise man one stated that one test is worth 1000 expert opinions. Like F&J suggested, I would be testing the ignition system. For the long term, ***uming you wish to keep the car, I would suggest looking for the other carburetor used by Oldsmobile in 1951 - a Carter 851s (Olds part number 560534). Guess that is more than 3 thoughts Jon.
Yes, Quit jumping around and go through a thorough diagnostic check. Electrical..... Proper spark? Condensor? Timing (advance working?) Remove a plug and lets see it. Fuel? Proper flow into carb? filter installed? Recheck fuel pump pressure at idle and at a higher rpm. Is your air filter clean, does your choke stay open when at a higher rpm and at operating temps? Adjusting idle screws only adjusts your idle, anything above idle is control by your jets ( which would need changed if that is the problem) Your Olds is just ***s!
I’ve had similar symptoms due to a bad coil. Your coil can be bench checked with an ohm meter but I suggest you find someone local with an oscilloscope to verify that the entire ignition system is working properly.
Take the carb apart and see if there is fuel in the float by shaking the float. Sounds like a bad float or float set too high.
O.k., took the carburetor back off and didn't find any dirt. Checked the float for holes/seepage, didn't find anything wrong there. Reinstalled the float and checked adjustment and, again, found nothing wrong. Reinstalled the carburetor, still hooked to the gravity tank, and it ran worse than it did before I removed it. Back firing, both through the exhaust and carb. Also with the engine shut off, I looked down into the throat and could see that gas was still running out. According to my 1950 - '51 Oldsmobile Shop Manual, it talks about making sure, when adjusting the float, that the "float tang" is properly resting against the balance spring. I found a picture, in my 1957 Motor's manual, of the float rod and balance spring but my carburetor doesn't have a balance spring! I remember seeing the holes where it was supposed to be but... it's not there. Nor is the fuel strainer that goes into the fuel inlet. Can anybody tell me, for certain, whether this is going to matter or not? If the float level and amount of drop is set correctly, does it matter what the tang is resting against? Also, does it matter if there isn't a "fuel strainer" present? This is just a filter, right? Or does it meter the amount of fuel entering the bowl as well?
The fact that you see fuel running in the throttle bores after shut down means one of two things. 1.) The float system is not shutting off fuel flow when the bowl is full, in which case you should see evidence of leakage around the top cover gasket. 2.) There is leakage from the bowl itself. Possible culprits include, a crack, a missing check ball in the accelerator pump circuit or power valve or a defective accelerator pump or power valve. A leak from one of these should show up in their outlets or in the throttle bores.
Paging @carbking That sounds a little like those float springs used to keep the fuel bowl level consistent in rough terrain, but I'm not sure. If so, it may not be absolutely necessary or the cause of the late unpleasantness, but as a rule, missing parts are not a good thing in a carburetor. Makes ya wonder, what else did some dumb *** leave out?
I agree with the two point's that you are bringing up, X-cpe. The question that I am asking is whether or not the missing parts could be contributing to the flooding issue's that I am having. Thank you, though, for replying.
Yeah, kinda what I was thinking! In my minds eye, I can't really see what difference either of them missing would be but then my minds eye has been a little bit foggy ever since the 60's!! Thanks for replying....
I would start with correct fuel pressure Clean fuel And confirm any missing parts Worn parts Warped or cracked casting for your carb Ignition Points Condenser Wired Cap rotor Coil etc. Check the engine, Compression test Leak down Hook up a vacuum gauge Check the timing chain for slop And correct base timing and advance etc. All this is about 2 hours of farting around with a cold beverage of your choice. Sometimes we can get the blinders on and see only one thing without taking in the whole picture Is there a “easy” carb to stick on this thing for quick diagnostic? I’m thinking swap a known good carb on for a quick test.
The "balance" spring used in the Rochester BB is NECESSARY, as it exerts additional pressure adding to the float's buoyancy aiding in closing the float. It is not used like the Carter spring-loaded fuel valve for off-road; this thing is necessary on level ground. Note my previous post about this being a one-year only carburetor and thankfully being obsoleted after one year. It is bad enough if perfectly restored. Missing the spring just makes it worse. Reiterating, Oldsmobile also used a conventional Carter carburetor part number 851s (Olds 560534). Jon.
I wouldn't be too hard on the "rebuilder"; probably the first one of these he had ever seen. The OP stated he had used the rebuilder before, and he knew his stuff. I would doubt very seriously that there are 5 currently working mechanics on the planet that have been inside one of these experimental carburetors. I have, and even if I were still restoring carbs, I wouldn't touch this one. Jon.
Well OK, though didn't realize it had been professionally rebuilt either. I am a little weary of people that apparenly have had a lot of parts left over when they repair something. A lot of my time has been spent cleaning up mistakes. As a general rule there aren't any "unnecessary" parts in a carburetor (or anything else automotive related for that matter) you can be sure the OEM would have left it out in the first place and saved the 1/4 cent if they thought they could get away without it.
Carb King hit on one VERY IMPORTANT point, That was a somewhat experimental carb that had issues from the get go. He also posted the Carter number for an also "correct" if correct spins your wheels carb that the Olds nit pickers can't point to and shake their heads. I'd hunt down the alternative carb or find a two barrel that bolts on that is a lot less subject to issues and be done with it.
Thank you Jon, I was hoping that you would chime in once again. I kinda had the idea that's what that "balance spring" was in there for. If they can save a penny they are going to do it, so yeah, no unneeded parts. I can't really get pissy with the rebuilder over this, I was in there 3 times before I realized it was missing, no telling how many times it has been opened up since it was left out. I know that the guy that owned it before the guy that I got it from was having issues with it over fueling. How about the strainer, is it there just as a filter? If they weren't wanting an arm and a leg for a WGD 851 I'd go for it in a heart beat. Hopefully, I can find the missing stuff and get a little use out of the BB. Anybody got a old Rochester BB that I can use for parts?
Many rebuilders leave out the filter attached to the fuel valve seat. As far as I am aware, Rochester was the only carburetor company to use this type; although others (Carter, Holley, and Zenith) used a much larger inlet filter. (Opinion) it is too small, and way too easy to clog. Would suggest leaving it out and using a good inline filter. Jon.
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