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From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
Chasing my tail on timing
I cannot for the life of me get my timing dialed in with these new weights and baseplate. If I use the springs to allow all in by 3000 rpm, when I hook up the vacuum advance, I've got about 38* total advance at idle. I also can't get 36* total with no vacuum advance without initial idle timing around 24* which then gives me too much with the vacuum advance.
If I use stiffer springs to prevent the mechanical advance from moving at idle, then I've got the distributor clocked way too far around to get enough advance and then it prevents all the mechanical advance from coming in where it's supposed to.
Am I just overthinking this? How much advance at idle should come from the weights and how much from the dizzy position.....or does it matter? Pertronix says these weights and base plate should allow for 23* of advance.
I don't understand what's going on. Even my old weights are working the same way where they seemed to work fine before I started screwing with everything.
New Pertronix stuff
Maybe my problem is the module clearly states "RACE ONLY"
You may also need to change the weights so that you limit the total amount of centrifugal (mechanical) advance. Read Lars' paper on timing for info on vacuum cans, etc.
If I use stiffer springs to prevent the mechanical advance from moving at idle, then I've got the distributor clocked way too far around to get enough advance and then it prevents all the mechanical advance from coming in where it's supposed to.
You can pull the HEI out and re-clock it one tooth. You'll have to align the slot in the bottom to re-install it.
With the vacuum advance 34*-36* is not unusual depending on your initial timing and the amount the vacuum pulls at idle.
If this is not a stock motor then it may be necessary to limit mechanical or vacuum advance or both to get the timing you want.
I limit the movement on both my vacuum and mechanical in order to get the initial I need and not exceed desired total or cruise timing.
are you sure you dont have the center plate upside down? look at the video below the plate is not installed the way you have it. The weights cannot fully return, they are hitting the bulged out side of the center plate.
Did you notice the orientation of the original plate before removing it?
I believe the gold springs are the lightest, set up your timing using them, you can always put in a stiffer set without having to redo the timing.
Disconnect the vacuum and cap the vacuum port until you get the mechanical right. Then, address the vacuum. You may have to add a stop so the vacuum doesn't move so far.
And if you get tired of this, I highly recommend the MSD E-Curve distributor (with or without an MSD-6 box). Lets you select mechanical and vacuum curves by just adjusting a small rotary switch in the distributor.
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
I have read just about every timing thread out there as well as studying Lars' excellent papers.
Looking at that center plate, it does look upside down compared to the video. However, the illustration in the Pertronix instruction sheet clearly depicts that orientation for clockwise rotation. You're right, though, seems like it would keep the weights from fully returning.
I'm wondering also if I need to remove the distributor and clean the shaft. Almost 40 years of accumulated gunk is probably stuck on it.
I'm going to work on it again tonight. Thanks guys
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
I think I've finally got it straightened out. Turned the base plate over (opposite the instructions) and used one gold spring and one copper spring. I get 36* now about 3200 rpm, idle with no vacuum is at 18* and 34* with vacuum. About 52* at 3200 rpm with vacuum.
Guess the next thing is to pull the distributor and clean the shaft but that's a project for another day. At least I can drive it this weekend now.
I think I've finally got it straightened out. Turned the base plate over (opposite the instructions) and used one gold spring and one copper spring. I get 36* now about 3200 rpm, idle with no vacuum is at 18* and 34* with vacuum. About 52* at 3200 rpm with vacuum.
Guess the next thing is to pull the distributor and clean the shaft but that's a project for another day. At least I can drive it this weekend now.
Glad to hear it was that simple. The plate just didnt look right to me.
Chasing my tail on timing
