Pulling a distributor can be intimidating the first few times you do it. The distributor, after all, is where the delicate dance between spark and compression is choreographed. Put things back wrong and the engine may not run or may run so badly it’s at risk of damaging itself. Then, even if things are put back together more or less in the correct way, they still require fine tuning.
To get yourself as close as possible to the right starting point, pull out something virtually everyone has, a test lamp (12V or 6V, as appropriate to your car), and use it to find the exact moment your points make contact inside the distributor. Then, when you go to actually start the engine, you’ll already be within a degree or two of the proper static advance.
I recently had to do just that on my ’62 Corvair after combining the worn-out original distributor with a much nicer one salvaged from a 1965 110hp engine. It made getting the car re-started a snap.
The Problem
For quite some time, I’d noticed my car had diminishing power on hills. Because it wasn’t that great to start with, that was a real problem. Although I’d installed a new distributor cap, plug wires, and rotor some time ago, I figured it was time to replace the points and condenser. Yet, imagine my surprise when I discovered they were both nearly new! It was clearly a deeper problem.
I turned to one of the best Corvair resources I’ve found yet: How to Keep Your Corvair Alive! by Richard Finch. The late Mr. Finch was a devotee of the raced and daily driven Corvair and offered up his book as a supplement to the GM-supplied shop manuals (which I also own—I insist on owning a shop manual for all my cars, otherwise I feel I’m just groping in the dark when I work on them).
In his initial tune-up instructions (which, of course, I’d never really gotten around to following until now), Finch describes testing both the vacuum and centrifugal advance systems. One problem, I quickly discovered, was that rust had formed between the centrifugal-advance weights and the plate on which they slide inside the distributor. I pulled them, gave them a gentle cleaning with sandpaper, and then reassembled things—confident I’d be back on the road shortly now that my mechanical advance was working again.
Except when I went to give it the test, the distributor shaft no longer moved when I turned over the engine with a wrench. That was a new and unpleasant development. Down inside the engine, the roll pin that holds the distributor gear had sheared. Something I only discovered once I pulled the distributor to investigate why it no longer interfaced with the engine.
The Solution
Getting new roll pins off the generic-parts rack at the parts store is thankfully no problem. But when I got my old distributor cleaned up for repair, I noticed that the cam inside was really showing its mileage. I think it was probably run without lubrication for a long time. It occurred to me that I actually had a second distributor from a parts engine I’m slowly disassembling. To my delight, it was like new inside and still even wearing what may have been its original points, condenser, and dust shield.
I pulled the rusty, crusty vacuum advance unit off, replaced it with the unit from my original distributor, and swapped in the advance weights for good measure. Then I installed the Frankenstein distributor and went to set the initial timing using another of the Finch tricks: using a test light to know exactly when the points open and close.
Getting the Car Started
No project like this can begin without knowing for certain that the engine’s number-one cylinder is at top dead center (TDC) on its compression stroke. That’s the moment the spark is timed to and thus the zero-degree spot when we’re talking about advancing or retarding the spark. Because the spark cannot instantaneously burn all the fuel in the combustion chamber, we’re trying to light it off just far enough ahead of time that maximum explosive effect occurs just at the moment the piston can be pushed back down in the bore.
Spark the mixture too far ahead of time and the piston is pushing down on a crankshaft that can’t yet turn in the right direction. It beats up the innards of an engine, can blow holes in the top of pistons, and definitely doesn’t help move the car forward. Retarded spark is safer for the engine, but because the explosion is kind of chasing the piston down the bore, it leaves a lot of power on the table.
The main method for determining whether the engine is at TDC is to remove the spark plug (removing or loosening all the spark plugs will make the engine turn over a lot easier) and then to place a finger over the hole to feel compression building—showing that the valves are closed in that cylinder. If no compression builds, the piston is likely coming up on the exhaust stroke instead.
Some people “bump” the engine with the electric starter for this. I prefer to have the battery disconnected and to use a wrench. It seems safer and more precise.
Once you know the engine is on the compression stroke, you can use the timing-alignment marks on the engine to put the piston at the proper advanced moment—a value found in your shop manual. For a Powerglide-equipped ’62 like mine, I needed 13 degrees. This requires too much precision to do by bumping the starter. With the piston in the right spot, now you can twist the distributor so that the points are opening at just that moment.
This is where the test light comes in. It is connected to the negative lead on the ignition coil and to the engine ground. The ignition is then switched on at the key (careful not to bump the starter). If the light is on, the points are closed; advance the distributor just until it goes off. If the light is off, the points are open; retard the distributor just until it comes on.
And just like that, you’ve gotten the engine within a degree or two of proper timing without a timing light and without cranking it over, twisting the distributor at random until it starts firing. I put my timing light on the engine afterward and it was essentially spot on, though I ended up dialing in a bit more advance just because my engine seems to like it.
But Then…
The result was incredible. The car has never had this much power. Despite the extra advance, it doesn’t ping on hills (a friend has suggested that’s because I have stuck rings and thus no real compression) and it’s downright exciting to drive now.
Or it was, the two times I got to drive it. Then the starter bit the dust… Tune in next time!
