Yes, the pinch nut is the one to loosen to rotate the distributor, with a
few caveats:
1. if you only need one or two degrees more adjustment, try loosening the
the two bolts on either end that go into the block. The front one is
still difficult to get at, but there is some play in the holes in the
base plate, and you can rotate the distributor this way a little bit
without touching the pinch nut.
2. the pinch nut is rather a last resort, in that it is so difficult to
get at, and that its scissor-grip on the thin-wall aluminum distributor
housing is so precarious. Be very careful not to over tighten this bolt,
and make sure the distributor is fully seated and square. If you've gone
to the trouble of loosening it, then run the vernier screw back into the
center of its range, and set the timing with the pinch nut. That way
you'll have plenty of adjustment either way with the vernier in the
future, and not have to mess with the clamp at all. Repeated tightening
of this clamp will inevitably crack the distributor housing, eventually
resulting in a distributor that won't stay timed.
My 2¢...
RobMGB@aol.com had this to say:
>I have 74B with 25D4 dizzy that has vernier timing adjustment. Vernier is as
>far as it can go in retarding timing and I still need to go a few degrees.
>Please someone confirn it is the pinch nut in the center of the clamping
>plate and not the bolt at each end that you loosen to adjust timing. The
>pinch bolt has a nut on the front that I can't get at with a wrench and a
>square head bolt toward the cockpit that I can't get a wrench on enough to
>loosen either.
>Fortunately timing is close which broadens the topic. Mine is 74B with
>rebuilt and un original block with rebuilt no-lead head and mild street
>grind
>crane cam. Have crane/allison electronic ignition which delivers a jolt
>occasionally when trying to turn that vernier on dizzy with hand bumping the
>plug wires and stainless oil cooler hose. Best I can figure from book is
>timing should be about 13 degrees at 1500 rpm. Anybody got any better
>advice.
>Runs great but could stand a little better gas mileage since it is daily
>driver.
>Robmgb
>74B
>
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Max Heim
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Studio L'Image/San Francisco
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