Post by erock482 on May 2, 2024 1:34:01 GMT -5
I'm dabbling in a 1951 CJ3A with a L134 and a Carter WO. Timing and Carb set up are where I'm a bit uncertain yet.
I've been through the carb chasing a stumble and die that would occur when you first cracked the throttle, but would then clean up once you revved through it once or twice, thoroughly cleaned all parts, have set the float level, as well as the accelerator pump travel to spec.
In true parts cannon approach, I rebuilt the carb and unstuck a rusted in distributor all at the same time. so we introduce timing into the equation as well.
Questions on the process of timing without a timing light
- With the carb idle stop screw threaded in 3 full turn from touch down on the base I'm about at max thread in for this screw, and when started the engine is idling about 1600ish RPM which seems a bit high, is this correct/typical or do I need to change something with the carb?
- With engine warmed up, I advance the distributor (Clockwise) and can increase the RPM, however there is a pretty wide range where it seems I can use the advance to push the RPM up while the vacuum stays about 20.5. If I understand this correctly I should continue advancing as far as it will let me before the vacuum drops, then reduce 100 RPM and lock it down. Is that correct?
- As we flip back to the idle stop, if I begin to back this screw out (Closing the throttle) I see a pretty rapid drop in vaccuum to 15 before things get erratic and its clinging to life, which leads me to believe the high idle with the screw ran down 3 full turns is possibly throwing me off here.
My brain is thinking the engine wants more advance, but the high RPM with the idle stop in is muddying the waters for me. If i bounce back and forth between backing out the idle stop (Closing throttle) and advancing the distributor I can kind of work things down to a more reasonable idle RPM in the 700's.
Once we get here if I slowly run the throttle up I get a pretty good stumble around midway where the low speed circuit cuts off and the high speed circuit cuts in, which makes me think the accelerator pump needs to kick in a smidge earlier?
At this point I'd just like a nudge to make sure I'm on the right path here.
For reference, the heat riser is working properly and I do not seem to have any vacuum leaks, plugs are fairly fresh since I got the engine running last summer.
I've been through the carb chasing a stumble and die that would occur when you first cracked the throttle, but would then clean up once you revved through it once or twice, thoroughly cleaned all parts, have set the float level, as well as the accelerator pump travel to spec.
In true parts cannon approach, I rebuilt the carb and unstuck a rusted in distributor all at the same time. so we introduce timing into the equation as well.
Questions on the process of timing without a timing light
- With the carb idle stop screw threaded in 3 full turn from touch down on the base I'm about at max thread in for this screw, and when started the engine is idling about 1600ish RPM which seems a bit high, is this correct/typical or do I need to change something with the carb?
- With engine warmed up, I advance the distributor (Clockwise) and can increase the RPM, however there is a pretty wide range where it seems I can use the advance to push the RPM up while the vacuum stays about 20.5. If I understand this correctly I should continue advancing as far as it will let me before the vacuum drops, then reduce 100 RPM and lock it down. Is that correct?
- As we flip back to the idle stop, if I begin to back this screw out (Closing the throttle) I see a pretty rapid drop in vaccuum to 15 before things get erratic and its clinging to life, which leads me to believe the high idle with the screw ran down 3 full turns is possibly throwing me off here.
My brain is thinking the engine wants more advance, but the high RPM with the idle stop in is muddying the waters for me. If i bounce back and forth between backing out the idle stop (Closing throttle) and advancing the distributor I can kind of work things down to a more reasonable idle RPM in the 700's.
Once we get here if I slowly run the throttle up I get a pretty good stumble around midway where the low speed circuit cuts off and the high speed circuit cuts in, which makes me think the accelerator pump needs to kick in a smidge earlier?
At this point I'd just like a nudge to make sure I'm on the right path here.
For reference, the heat riser is working properly and I do not seem to have any vacuum leaks, plugs are fairly fresh since I got the engine running last summer.
