| Slant Six Forum https://www.slantsix.org/forum/ |
|
| Super six BBD carb shaft leak - fact or fiction https://www.slantsix.org/forum/viewtopic.php?t=9976 |
Page 1 of 1 |
| Author: | Slant6Ram [ Fri Jul 30, 2004 12:17 pm ] |
| Post subject: | Super six BBD carb shaft leak - fact or fiction |
I understand that big problems happen when the mixture is adjusted properly for a new carb, but year later, the engine runs lean due to the leak forming over time. So it's a real concern, and shouldn't be ignored. My point being: Lots of air is always moving through that carb, so a -little- leak should be pretty easy to account for with the idle screws or metering rods adjustments. (true/false?) But, I'm no expert, that's why I'm asking. Is the fuel mixture process really that delicate? Is a little leak at the throttle shaft cause to go surfing ebag for a "new in box" carb? Can't I use a spring loaded o-ring or felt seal on the drivers side and epoxy a small cap over the other end. Don't want to start a fight, just looking for some respectable feedback on a much talked about failure issue. |
|
| Author: | Reed [ Fri Jul 30, 2004 1:03 pm ] |
| Post subject: | |
The problem is wher the air enters the carb. When air flows down the throat of the carb (where it is supposed to go) the air passes by the correct ports in the throat of the carb and creates a vacuum which draws the fuel out of the carb in the correct amount (this is an EXTREMELY oversimplified explanation, but will work for this answer). As you know, an engine runs lean when there is too much air in the air/fuel ratio in relation to the fuel. The problem with throttle shaft leaks is that the air enters the carb after all the ports where fuel is drawn out so the same amount of air enters the intake manifold but not enough fuel is drawn out of the float bowl to match the amount of air (the air at the shaft leak does not pass by the ports so no fuel is drawn out). This is why you can compensate for the air leak at idle with the mixture screws but as soon as you open the throttle (and the idle circuit is no longer the main source of fuel to the engine) the leak will create a lean condition. Hopefully this is correct and will help. I'm sure some of the other more knowledgable folks here will correct me if I'm wrong. |
|
| Author: | mnecaise [ Mon Aug 02, 2004 12:03 pm ] |
| Post subject: | |
fwiw, I've seen carbs where the engine wouldn't idle because of air leaks around the shafts. WAY too much air & the idle jet couldn't compensate because the idle circuit was being bypassed. Sometimes you can rebush the carb. Sometimes you can rig up a rubber or felt shaft seal that'll fix the problem. Sometimes you need to replace the carb. Depends on how bad it is & what carb you're dealing with. Eventually, if the shaft becomes sloppy enough, the butterfly will start to hang up. This usually shows up as the throttle sticking open, which sometimes leads to accidents. |
|
| Page 1 of 1 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|