Slant six distributor drive gear

Kevin, it's difficult to tell whether you're a failure as a comedian or a failure at discerning technical drawings from illustrations, but practically speaking it doesn't much matter which kind of failure you are (and I am very pleased to make sure you're a failure at deliberately disseminating false and misleading information to those who asked a legitimate question in good faith).

Original poster (and anyone else who needs to do the subject repair job): Installing a slant-6 distributor drive pinion properly is not difficult. There is no tricky inconsistency in hole placement to trip you up. There is no substantial risk of getting it wrong and having it fail. All you have to do is follow the procedure—the real, actual, correct procedure that's been used successfully for nearly fifty-one years now, not the one Kevin has made up in an apparent effort to make himself feel important or something—and you'll have a successful result.

Here are two versions of the (real) slant-6 distributor drive pinion installation procedure—first, from the service manual:

Align gear teeth with centerline of rotor electrode. If gear is worn or damaged, replace as follows:

A) Install lower thrust washer and old gear on lower end of shaft and temporarily install roll pin.

B) Scribe a line on end of shaft from center to edge. The line is centered between two gear teeth as shown in fig 5. Do not scribe completely across shaft.

C) Remove roll pin and gear, use a fine file to clean burrs from around pin hole.

D) Install new gear with thrust washer in place, with hole in gear rotated approximately 90 degrees from old hole in shaft and with scribed line centered between the two gear teeth as shown. If it appears the new pin hole may interfere with the shaft oil groove, rotate gear to the centerline of the next pair of gear teeth, aligning again with scribed mark on the end of the shaft.

E) Before drilling through shaft and gear, place a 0.007" feeler gauge between gear and thrust washer, and after again observing that the centerline between two of the gear teeth is in line with centerline of rotor electrode, drill a 0.124" to 0.129" hole and install the roll pin.

CAUTION: SUPPORT HUB OF GEAR WHEN INSTALLING ROLL PIN, SO THAT GEAR TEETH WILL NOT BE DAMAGED.

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Now, my own writeup, with less scribing and more realism:


When you examine the new gear, you will see that a hole has already been drilled in the gear housing, and on first glance it will look as if this is meant to accept the roll pin. No. You must not use the single hole that is drilled in the gear when you purchase it. It's just an index hole for easy visual reference of the gear's position as you install it.

Push the top (rotor end) of the distributor mainshaft down towards the drive end. Place the new thrust washer over the drive end (bottom) of the shaft. Maintain downward pressure on the mainshaft, and fit the new nylon pinion on the drive end of the shaft with the existing single hole in the new pinion at right angles to the hole in the distributor mainshaft. Hold a 0.007" feeler gauge between the gear and the thrust washer, then ensure that the pinion is fully seated (all the way down) on the shaft.

Once you've positioned the new pinion correctly, drill through the pinion such that you create two holes exactly in line with the existing distributor mainshaft cross hole, taking care not to enlarge or ovalize the mainshaft cross hole, as this would allow the pinion roll pin to come loose.

Using an appropriate hammer and punch, drive the roll pin home such that it is even on both ends, does not protrude overly much from either side, and engages both sides of the nylon drive pinion.

Now that the distributor's fixed, how do we put it back in in the correct position? The distributor timing was lost completely when the rotor stopped turning and the engine kept on. You'll have to do it from scratch. The timing mark on the vibration damper can't necessarily be depended on as correct, for the outer ring member of the vibration damper—which carries the belt load—tends to slip relative to the inner hub, which causes false indications of overly-advanced timing.

First, you have to find true Top Dead Center. Pull the frontmost (number 1) spark plug, straighten a wire coat hanger, insert the end into the spark plug hole, and turn the engine using the fan and fan belt until the hanger stops moving upwards. This is TDC, and you've got a 50/50 chance that it's the correct TDC (the one between the compression and power strokes). With the frontmost piston at TDC, have the distributor rotor pointing towards the number-one spark plug wire tower of the distributor cap,
which is in roughly the 4:00 position. The drive pinion for the distributor is helical, so the rotor will move about 30 degrees clockwise when you push it home into the block; when you're aiming for a 4:00 position, start at about a 3:15 position before pushing the distributor into the block.

If you're fortunate, this will get the timing close enough for you to start the engine and dial it in correctly, but that helical distributor drive pinion can make a nuisance for even those of us who've removed and installed slant-6 distributors countless times. It can seem for all the world like everything's exactly where it's supposed to be, and yet the durn thing won't start! I usually just remove the distributor hold-down bolt, note the position of the rotor, carefully pull the distributor out, very slightly turn the rotor clockwise and push the distributor back down, thus advancing it by one tooth. Snap the cap back on (don't bother with the hold-down bolt, as long as you can see the hold-down bolt hole in the block through the distributor hold-down plate slot, you're fine), and crank the engine. If still nothing, advance the distributor one more tooth. Keep repeating this, and sooner or later you will get some activity under the hood. It'll likely start with a change in the starter sound — either the starter will struggle and hitch, or it'll spin faster as the engine "tries" to start, or maybe you'll get a "POOF!" spitback through the carburetor. Keep advancing the distributor a tooth at a time until the engine fires and runs. If you don't get a good result within four teeth, go back to your initial rotor position and start moving counterclockwise from there, a tooth at a time. One way or the other, as long as the distributor is hooked up(!), sooner or later you'll get a good result. Once the engine will start and run, move it one more tooth to see if the engine runs better or worse. If better, leave it there. If worse, go back one tooth. Then reinstall the hold-down bolt loosely, set your timing by the normal procedure with a timing light, and tighten down the bolt.

Once you've done all of this to 5 or 10 Slant-6 engines, actually doing the job will take less time than it took me to type this out.