Spark Plug Advice Needed

Yes, NGK 5 heat range would be best. Using Manifold connected Vacuum Advance [ MVA ]. A reallllllllly good idea with that cam.

But you have to get it [ idling timing ] right first. You adjust the carb last.

This is how you do it. Disconnect & plug the VA. Engine idling, in gear if auto, starting with the dist giving about 10-12* at idle. Turn the dist slowly to advance timing until you have the highest idle speed. Now check the timing. My guess is it will be in the 20-35* range. Whatever it is, it is what THAT engine needs.

So let us say you got 26*. You can use any combination of init + MVA to give 26*. If you were using 12* before, you can add 14* with the VA unit. You will probably need to make a stop to limit total timing added by the VA arm. This is ALL part of tuning once you deviate from stock.
With this done, re-adjust carb idle setting. I doubt the met rods will need changing once timing is correct because running with insufficient timing makes the engine inefficient & it uses more fuel to cover the inefficiency.

Things to note:
- you need an adj VA unit. None of the above will work with a stock unit. Even if you have to buy a new dist....
- adjust Allen screw in the VA fully CW.
- see below on idle timing
- the carboned up valves is from oil leakage past the valve guides, NOT richness.

img307.jpg