[AdamIsAdam]

UPDATE: I installed my modified vacuum advance unit. It's P/N VC1849/AR19. It begins advancing at 4-6" of Hg and is all in by 7-10" providing 12* of distributor timing (24* crank timing). So I had the travel limited by welding in metal. Total travel is .12" which provides 10* of advance at the crank, exactly as Cliff said it would. And it works as promised.

Results: Still with 15* of initial timing and now +10* of vacuum advance added, the cold start-up and cold driving was wonderful. Driving was all around excellent. There was a SLIGHT surge felt at a steady 3,000 RPM which I'll come back to. So on to APT and temps:

But... (you knew this wasn't going to end so fast)...

I'm still running at higher temps than I used to with the Holley. Around town on a lovely, 75* fall day, it idles at 180* and goes to about 185 (MAYBE 190) around town. But after a long steady highway drive, it settles in at about 200*. Once up at that temp, it'll only go back down to 185* or so if I'm idling for a long time.

So I adjusted the APT screw CCW. I started with 1/2 turn, then a full turn, and the surge was diminishing. I went one more 1/2 turn for 1.5 turns CCW total from the 2.5 that Cliff set it at when he built it. The surge subsided further, but it's ever so slightly detectable. I'd be fine with the car if the temps weren't still 200* on the highway.

To me I think I still need less vacuum timing, since the surge is gone when no vacuum advance is connected. But the temp situation really has me annoyed.

As a reminder, I have a new 160* high flow, tested t-stat, a Ford Taurus electric 2 speed fan that's automatically on at about 170, and I run Evan's Waterless coolant that doesn't boil until 375*. Oh, and I have a home made wire/spring inside the lower radiator hose. I have a new one from Ames that I can install when I get around to draining the system again. The hoses are in excellent shape. The water pump I believe is the right type but I didn't pull it apart to check and clearance it because the car ran cooler with the Holley.

Thoughts? Next steps? Timing? A/F issue? cooling system issue? What next?