Ignition Timing and Valve Adjustment
A couple of issues right up front. First, the vacuum canister is kaput. So if I want that, a replacement will be necessary. Second, I couldn’t adjust the timing any more than it was because on one end that slotted adjustment tab was limiting; and on the other end, the backside of the vacuum advance mechanism was interfering with the front-most carb/intake flange. So I started off by removing that tab and fashioning a clamping mechanism using the piece I cut off and a fender washer. This will enable me to alter the distributor “stab” and rotate the housing by 90 degrees or so eliminating the interference with the intake manifold flange. I also temporarily blocked off the port vacuum source on the front-most carb — this to get ready to hook up the vacuum advance canister to full manifold vacuum.
In the meantime, I discovered I could get a vacuum canister from Rock Auto for about $60; but I could get the whole new distributor for about $85 – so I ordered one. Figured I could experiment with the one in the car and when I had it working like I wanted – modify the new one in the same manner. When it arrived I promptly cut off the adjustment slot.
Mechanical advance is added when centrifugal weights swing out against the springs and the pin you see moves from one side of the slot to the other. To limit it, I have to limit movement of the pin in the slot.
I did that by fitting a small metal sleeve over the pin and attaching a nylon tie-wrap to one side of the slot. By removing the heavier of the two springs, I knew total advance would come in at a much lower rpm — to be confirmed with the timing light.
I discovered that the rotor had quite a bit of play in it – so I fashioned a paper “shim” that wedged it much tighter on the distributor shaft.
Last, I used calipers to mark off some more advance marks on the crank pulley so I could see what the timing was doing at rpm with an old-school analog timing light.
The vacuum accessories (dizzy canister and brake booster) were all being run off of the vacuum of just one intake runner — there is no common plenum to pull from. So I was able to get fittings to connect all 4 runners to a common vacuum hose and run the booster and canister off of that line. Much more stable vacuum signal for the dizzy and the booster.
Running MUCH better – now on to balancing the carbs.