broker-len Posted May 29, 2017 Share Posted May 29, 2017 this is a updraft with the main meetering adjustment under the bowl have rebuilt it a few times new bowl gasket checked the float tried a few needle and seats car runs and idles ruff the idle screw make no difference i in adjustment runs the same if it is all the way in running it on a 32 PA plymouth what do you think ? Link to comment Share on other sites More sharing options...
robert b Posted May 29, 2017 Share Posted May 29, 2017 on some bb1s i have found that the idle hole drilling down near the float vent hole is some times cross drilled into the vent hole allowing to much air into the idle system and gives similar results to what you have described , all so a flat spot on throtleing under load . just a thought bob Link to comment Share on other sites More sharing options...
F&J Posted May 29, 2017 Share Posted May 29, 2017 13 minutes ago, robert b said: allowing to much air into the idle system and gives similar results to what you have described , all so a flat spot on throtleing under load Yes a lean idle mix can allow a flat spot at very light acceleration, but not too far off the idle speed. There is an old Mechanic's term of "90% of carb issues are electrical". Meaning make darn sure the ignition parts and all settings are perfect before climbing into the carb. The ignition system & settings can sometimes cause the same symptoms as carb issues. An oldtimer I know with 30 pre 1932 cars, has several known good updrafts to start old barn finds. He says he just clamps them to the intake if bolt holes don't line up. Then after he dials in the rest of the engine really nice, then he puts the correct one back on, and if there is now a running issue...it IS that carb, and can be nothing else. Link to comment Share on other sites More sharing options...
Mark Shaw Posted June 2, 2017 Share Posted June 2, 2017 (edited) If your BB1 has a hole in the surface of the mounting flange, make sure the gasket does not cover it. Note the flange gaskets with holes and slots shown in the pdf below. Carter BB1 Carburetor Instructions and Parts List.pdf Edited June 2, 2017 by Mark Shaw (see edit history) Link to comment Share on other sites More sharing options...
broker-len Posted June 3, 2017 Author Share Posted June 3, 2017 thanks every 0ne-------for some reason I am getting a situation where the idle screw makes on difference will idle with it all the way in may be one of the jets is bad,,,, am rebuilding one of the brass bowl carbs that came standared am going to try it if still the same going to look at coil Link to comment Share on other sites More sharing options...
Mark Shaw Posted June 3, 2017 Share Posted June 3, 2017 This might also help... Link to comment Share on other sites More sharing options...
PFitz Posted June 4, 2017 Share Posted June 4, 2017 12 hours ago, broker-len said: thanks every 0ne-------for some reason I am getting a situation where the idle screw makes on difference will idle with it all the way in may be one of the jets is bad,,,, am rebuilding one of the brass bowl carbs that came standared am going to try it if still the same going to look at coil Typically, when the idle needle screw loses all affect on engine speed, there is a leak supplying excess fuel from somewhere. Running rough is another indication of that. If the float level is too high it can cause the same problems. Happens often when someone added an electric fuel pump without checking fuel pressure specs. If the electric pump has a higher output pressure than the original mechanical pump, or vacuum tank it raises the float level. Every increase in fuel pressure can raise a float level about 1/32 inch per pound of pressure increase. Some updraft carbs are very sensitive to float level changes at low idle speeds. Can also happen when a novice "rebuilds" updraft carbs with just a gasket kit thinking that's all that is needed. If there are submerged brass fuel valves, they need to be replaced with new, or have the valve seats lapped so that they seal as designed. Years of alcohol gas can erode the sealing surfaces of brass valves/jets leaving then unable to seal properly. Same happens to the brass seats for the check valves in fuel pumps. The surface erodes and looks "textured" like it was sand blasted. That rough surfaces does not allowing the check valves to seal well enough, thus lowering pump output pressure. Any submerged springs controlling those valves can be erodes, too, thus weakening and not allowing the valve/jet to seal sufficiently. Some early diecast (potmetal) carbs can develop cracks internally and "bleed" fuel through the thin walls separating fuel passageways, thus bypassing the jets/restrictions that control fuel flow. With age, potmetal can become porous, too. Most reputable carb rebuilders will not work on diecast carbs from the 20's and early 30's for that reason. Paul Link to comment Share on other sites More sharing options...
broker-len Posted June 4, 2017 Author Share Posted June 4, 2017 (edited) thank you all so much----------good advise I guess I can replace all the jets or get it professionally rebuilt but just don't want to spend the money when it is not the original carb and I do have one will try the brass bowl as soon as I have the time Edited June 4, 2017 by broker-len / (see edit history) Link to comment Share on other sites More sharing options...
carbking Posted June 4, 2017 Share Posted June 4, 2017 (edited) The most common cause of the idle adjustment (mixture) screw having no effect is a defective engine valve. This causes the tuner to adjust the throttle positioner screw in further than normal opening the throttle butterfly further than normal. If the throttle butterfly is open beyond its range, it effectively removes the idle circuit from the carburetor. Second most common cause would be the adjustment in the above paragraph. A third, although rare, cause is installing the throttle butterfly upside down. When the throttle butterfly is open beyond its normal operating range, the dynamic area between the throttle butterfly and the throttle body is increased, thus lowering the velocity of idle air to the point where there is insufficient negative pressure in the idle pickup point to allow the idle circuit to function. Result: the idle will not change if the mixture screw is completely seated, or removed and placed in the pocket of the tuner. First approach - compression test. All of the above assuming that BOTH sections of the idle tube were removed and passages cleaned when the carb was rebuilt. Failure to remove the hidden lower idle tube and cleaning the passage below will also cause problems. Jon. Edited June 4, 2017 by carbking (see edit history) 1 Link to comment Share on other sites More sharing options...
F&J Posted June 4, 2017 Share Posted June 4, 2017 23 hours ago, broker-len said: thanks every 0ne-------for some reason I am getting a situation where the idle screw makes on difference will idle with it all the way in may be one of the jets is bad,,,, am rebuilding one of the brass bowl carbs that came standared am going to try it if still the same going to look at coil Can I say something without causing issues? You are all over the place...timing,..wondering about a bad jet, if not... a coil. >>, all over the place, is nothing more than either refusal to take diagnosis advice, or not hearing it said...like nobody here ever mentioned one point to test. One thing that bugs me, is a shop that just keeps throwing stuff at a problem, as their way of diagnosis. Link to comment Share on other sites More sharing options...
broker-len Posted June 5, 2017 Author Share Posted June 5, 2017 Sir-----thanks for your response this motor was rebuilt checked valve settings, checked compression 60 in all holes checked timing and points condenser is newer,,,, checked for vacuum leak the plug wires are older but does not explain my problem the plugs are black and the idle screw does not seem to affect anything was told low coil out put could cause this kind of problem I have rebuild the BB1 a few times with a new bowl gasket I am not a professional but not a novice either since the BB1 is not original for car and I have a brass bowl will try that before I start putting money in a BB1 professional rebuild if I still have issues will try a different coil after that will make a planter out of the car Link to comment Share on other sites More sharing options...
broker-len Posted June 5, 2017 Author Share Posted June 5, 2017 thank you carb king---did not take butterfly off have had this carb for ever I think I used to drive with it before it was rebuilt with better success -----I will check it Link to comment Share on other sites More sharing options...
hchris Posted June 5, 2017 Share Posted June 5, 2017 57 minutes ago, broker-len said: Sir-----thanks for your response this motor was rebuilt checked valve settings, checked compression 60 in all holes checked timing and points condenser is newer,,,, checked for vacuum leak the plug wires are older but does not explain my problem the plugs are black and the idle screw does not seem to affect anything was told low coil out put could cause this kind of problem I have rebuild the BB1 a few times with a new bowl gasket I am not a professional but not a novice either since the BB1 is not original for car and I have a brass bowl will try that before I start putting money in a BB1 professional rebuild if I still have issues will try a different coil after that will make a planter out of the car "the plugs are black" - not sure what the cause is, but certainly too rich. Link to comment Share on other sites More sharing options...
trini Posted June 14, 2017 Share Posted June 14, 2017 I have a similar problem with the BB1. The idle screw makes no difference. Old screw, new screw, same thing. The mounting gasket has 4 cut outs on the inside perimeter so there is no way to make a mistake in installing. I idle the engine using the jet underneath the bowl . My engine is also rebuilt. At the moment I am doing a ground up rebuild. so tuning will take a holiday. (1928 dodge senior) Link to comment Share on other sites More sharing options...
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