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Resolving the Distributor Issue
Replacing the stock Stromberg intake manifold with one for Dellortos
creates a clearance issue with the distributor vacuum advance. In its
original position, the vacuum advance bellows will hit the Dellorto
manifold cooling water tube and either prevent manifold installation or
adjustment of the distributor. Neither is good. There are two commonly
used approaches plus the one I finally settled on:
1. Rotating the distributor 180 degrees from the “normal” position and
repositioning the spark plug wires accordingly. This preserves the
functionality of the vacuum advance (although it may not be needed), but it
also puts the knurled nut that allows fine tuning of the ignition advance in an
impossible-to- reach position.
2. Removing the vacuum advance mechanism altogether. This solution
requires that the plate inside the distributor be pegged to the distributor
housing with a set screw or wired in place so it does not spin. This solution
disables the vacuum advance (European JHs with Dellortos did not have a
vacuum advance) is simple and keeps the distributor and spark plug wires
in the same position, but it requires removal of the knurled nut mechanism
that allows fine tuning of the ignition advance.
3. Removal of the vacuum advance bellows. This solution requires that the
vacuum advance bellows be removed, the housing ground down, and a
plate be installed where the bellows existed to prevent movement. This
solution disables the vacuum advance (not needed anyway), but it keeps the
distributor and spark plug wires in the same position and it allows the
accessible functionality of that neat little knurled nut ingition advance
adjustment I love.
Obviously, I chose solution number 3. Here is how (with pictures below):
1. Clean any oil buildup from the distributor
2. Remove the distributor cap and rotor
3. Remove the small retaining clip on distributor advance rod - the one that
keeps the knurled nut from unscrewing all the way.
4. Unscrew the knurled nut forcing the distributor advance rod and bellows
mechanism from the distributor body. At some point you will have to lift the
vacuum advance spring rod free from where it connects to the distributor
plate. If you don’t, you will not be able to free the rod and bellows
mechanism.
5. Remove the vacuum advance rod and bellows mechanism. Be sure to
keep any little parts for reinstallation.
6. Hack saw or bend the metal bellows housing so you can remove the cap
and expose the rubber bellows. Discard the cap.
7. Remove the spring rod and attached bellows from the spring rod housing
and cut the rubber bellows completely off with a razor knife or scissors.
8. Reinstall the spring rod in the housing. Notice that there is nothing to hold it
in place. The next steps are to fix the spring rod in place.
9. Select a common flat washer from your junk drawer/can that is somewhat
larger than the disk on the end of the spring rod, but considerably smaller
than the bellows mechanism was. We want to bolt that washer over the disk
on the spring rod to hold it all in place.
10. Drill three equally spaced holes in the washer and in the vacuum advance
housing and bolt it all together with some small fasteners.
11. Cut and grind the remaining vacuum advance bellows housing down to the
same diameter as the washer.
12. Reinstall in the distributor vacuum advance assembly as shown in the
pictures, below, reengaging the knurled nut and the retaining clip. Adjust
the knurled nut so the modified advance mechanism can be adjusted in
either direction after installation on the auxiliary housing. The reduced
diameter of what used to be the bellows mechanism will not interfere with
the intake manifold now, and the knurled nut fine ignition advance
adjustment can still be used.
Click for larger picture
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