So I'd like to tune my carb, but I'm learning.... Just watched your video and will attempt to follow your instructions. However, I need to buy a vacuum gauge, and I need to know where do I connect the vacuum line? Secondly, I have modified my distributer with electronic ignition. So I should be concerned with dwell... right?
Standing at the fender of the driver’s side looking in to the motor. On the right side of the intake manifold should be a threaded port from which vacuum is drawn for the windshield wipers. In the video above you can see it under my hand at the 5:00 minute mark. That is where you connect the vacuum gauge. Trying to measure dwell in a CD ignition system is problematic. Any reading you get will be fluctuating too much to make any real determination. This is why I don’t recommend CD Ignition for these old motors. Proper and timely maintenance will keep a Points and Condensor Ignition system going for as long as they make parts.
Hi Rick, I just watched your video on how to adjust the timing with no timing light. I have a question. I also wrote down the steps as I understood them, but I can be a little dense at times, so if I am missing a point or a critical piece to this process, please correct me.
Step 1. After verifying the points are adjusted to .020, we now adjust the timing by watching the RPMs as we turn the distributor. You show us the RPMs dropping and settling based on how advanced or retarded we are with our distributor adjustment.
I believe you want us to find this center point, but then you mention something about adjusting the distributor to drop the RPMs down 100 before the next step. This is where I get a bit confused. Can you clarify why we are doing this and are we advancing or retarding the distributor to achieve this?
Step 2. Now we are to adjust the ‘idle stop screw’ to maximize the vacuum.
I understand this video explanation perfectly, but I always thought we were adjusting idle RPMS with this adjuster. Never considered it would improve the vacuum.
Step 3. The video now explains that we will be adjusting the ‘idle mix screw’ to achieve the best idle RPMs with a goal somewhere between 600-700 RPMs.
This is more clear to me than before. I’ve never quite grasped what we were achieving with this adjustment, so I always pretty much left it between 1.75 to 2.25 turns out.
Again, this is more for me to work through the steps in my own head, but would really appreciate some clarification.
When warmed up, loosen the distributor lock screw and while watching the vacuum gauge, slowly rotate the distributor until you have achieved the highest vacuum reading you can.
Your attention now shifts to the Dwell/Tach. While observing the Dwell/Tach RPM scale, Note the reading. Now, back the distributor off 100 RPM and lock it down.
By manipulating the distributor, you're altering the timing to fire at the best possible point in the compression cycle. Backing the RPM down by 100 allows the fine tuning of the vacuum in the next step.
By manipulating the Idle Stop screw, you're altering the level of exposure of the vacuum port in the throttle to increase the vacuum to it's maximum thereby conditioning the flow of the air/fuel mixture to make it even across the intake.
Idle RPM is set using the mixture to match fuel flow to air flow (vacuum pull)
Got it. I missed the step to back off the Dizzy while reading my vacuum gauge. On my last effort, I got the best vacuum I could while adjusting the distributor, but tightened it down right there. My Jeep still ran okay, but seemed a bit sluggish under acceleration.