moper said

I think there's a few potential issues with this.
1st - the "opened crossover" more than likely means the factory apssage under the intake or possibly in the heads was plugged by carbon deposits. The '68 318, and any 273 would not have had any provision for EGR.

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moper said

2nd - the pinging. I'd look at two things:
The carb jetting which is probably 2-3 steps leaner than it needs to be for the pump unleaded we buy now. Pull the top off the carb, find the main jets, and using a drill bit enlarge them very slightly. A little goes a long way. If you have pin drills, and wire gage bits, those are the best way to sneak up on the right jet size. You also want to make sure the power enrichment circuit is working. It might not be.

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moper said

The timing curve is suspect. You need to know how much timing there is, what advance is putting it in, and when. You can ajust the mechanical advance with tweaking springs, slots, and weights. And you can adjust the vacuum advance but only the amount of vacuum required to move it - not the actual advance amount using that 11/32 hex key. My impression is there are lightweight springs in it (should really only be one, the other should be the factory "light" which is 5 times stiffer than the HP light springs) and the mechcanical is advancing too much. Get a timing tape and use that and a tachometer to fully map out your timing curve. Then post that.

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