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| Cutting out at takeoff https://slantsix.org/forum/viewtopic.php?t=57831 |
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| Author: | Essentialt21 [ Sun Jun 07, 2015 4:19 pm ] |
| Post subject: | Cutting out at takeoff |
Hello again, Car is idling great, starts great, drives great and takes off great from a strong pedal, but if i feather the accelerator and do a slow soft takeoff from a stop the car cuts out and almost dies on me. I can remedy this by punching it real quick, or really lightly increasing the gas till it gets over the "hump". This is driving me insane. I have a 1966 plymouth belv II with 225 and a holley 1920. Holley was rebuilt, timing adjusted, valve lash adjusted, just replaced fuel pump did fuel line re-route, also checked the accelerator pump and that has a nice healthy squirt, the choke is fully open when it is warmed up to drive. The one thing I noticed is that there is a slight vacuum leak at the holleys throttle shaft bushings, I am wondering if this leak is even significant enough to present itself as an issue, having a bad feeling this could be my problem. Any and all advice is welcome, this forum has taught me a great deal. -Shane |
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| Author: | wjajr [ Mon Jun 08, 2015 5:52 am ] |
| Post subject: | |
Quote: Car is idling great, starts great, drives great and takes off great from a strong pedal, but if i feather the accelerator and do a slow soft takeoff from a stop the car cuts out and almost dies on me.
Quote: I can remedy this by punching it real quick, or really lightly increasing the gas till it gets over the "hump".
This is classic lean idle condition. When you stomp the gas accelerator pump covers up lean idle condition and transition circuit, and once running on main jet and enrichment circuit where engine responds correctly. Just what is the reason idle is lean needs to be discovered. Sloppy throttle shaft is one source of additional idle air, and or lean setting of idle mixture screw is another, and perhaps some other source of extra air entering down stream from carburetor. You may be able to turn out idle mixture screw a bit to mask the shaft air leak. Transition mixture circuit is also controlled by idle mixture screw. Second cause could be the way idle speed is controlled. Often when too much of transition circuit slot is exposed at idle it will cause a big flat spot or bog when taking off. Back off idle speed adjustment screw which closes down amount of transition slot exposed, closes down throttle opening which reduces amount of air entering while running on idle, and conversely idle air/fuel mix becomes richer. Then adjust timing to bring up idle rpm, and reset idle mixture screw. So it boils down to two possibilities, and or a combination of both. Is there too much extra air entering from worn part or ill fitting gaskets, or are carburetor settings off because throttle plate stop screw is set such to allow too much air passing by? |
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