Distributor Specs

[John Rogers]

First: Does anyone know the radial and axial clearance specs (or max sloppiness) for the distributor in a 1974 2.0l 914? I have looked everywhere (including email to Bosch) and none to be found. The folks in San Diego say "not too much"? We have a problem with dwell changing and things seem a little loose to me. Second: Is the advance plate supposed to be fully retarded with engine off or in the middle of it's travel? Ours is in the middle, seems a little unusual?

[JP Noonan]

Well in my per-fessional o-pin-onion I would say about two-thousandths less than too much, and about three-thousandths more than not enough.

Seriously it should not "wobble", if it does then most likely the bearings lost lubrication and seized up. Some of the electric ignitions (the one that replace the points, not CD boxes) claim to negate the effect on an out of tolerence dizzy shaft. I guess that a wobbly shaft can change the dwell as RPM's increase.

What I would do (yeah, like that means anything) is to turn the dizzy (take it off the motor first) so one of the cam lobes opens the points. Measure with a feeler gauge the points gap. Then try to move the shaft, without turning it, back and forth to see if it changes the points gap significantly. I know, not a lot of help, but it's an idea.

As for the advance plate, it sounds like either where the two plates pivot (in the center of the two plates is a hollow pivot point) some rust has formed. Or rust is on the little ball bearing that keeps tension on the plates. Or the vacuum advance canister is broken, it has a diaphrame inside that "might" have bent or something, try using a vac pump on the can and see what it does. Looking at mine in the car the little ball bearing is all the way toward the vac can. The little springs on the advance weights only affects the shaft the rotor is on, but FYI my rotor seems to be fully retarded at rest. To get the plates out, step 1. Remove all the screws. Remove the condenser, vac can, and dist cap catches. The plate should pull out with little effort. Then take the ball bearing off and the plates should separate. I lubed mine with Bosch dist grease after having problems with rust using 3in1 oil.

[Dave at Pelican Parts]

Remember that all of the stock (FI) distributors have a vaccuum retard function.

When you have the engine shut off, the springs in the distributor take out all of the centrifugal advance. There is also no vaccuum on either the advance or retard ports on the distributor dashpot. But if you applied a vaccuum to the retard port, the points plate should move in the "retard" direction. Which means that there should be some "slop" in that direction when the engine is off.

--DD

[John Rogers]

Thanks for the info. I thought the retard would only come in with vacuum on the diaphram. There was a problem with rust in the distributor as we had it rebuilt severl months ago but I think that is what caused the internals to wear out. The shop I deal with had a rebuilt one and I put it in and the misfires and roughness went away. By the way JP did you get that software to work?