It's a good question to ask whether it's safe. I'd hate to tell you it is safe purely based on advancing initial timing alone. The cat pi$$ they sell as unleaded gasoline today is not the same as the leaded (high octane) gasoline's they sold in 1966 & you can expect variation(s) in performance based on timing alone. Mid-to-Late 60s we were buying low grade regular leaded gasoline with an octane level of 93. Premium grade was ~99 octane - yeah, big difference in fuel in 60 years of petroleum gasoline. I'd try bumping initial to ~10°.

droldsmorland provided some excellent suggestions Post #16

 

Well, I've made some progress with this (I think). I got thinking about it and I had a feeling that something was going on with the primary rods.....like maybe the wrong power piston, spring, or rods was installed. This is a bit of a frankencarb after all (it's my backup carb while I get my original restored).

Took it apart today and sure enough, wrong primary rods. It is supposed to have 44 rods, it has 49B rods installed instead, Everything else appears right. I will install the spare set of 44 rods that I have and report back!

 

Yes sir! That's what it was.......replaced the 49B's with 44's and it runs like a champ!

 

Nice!
Glad it worked out

 

Excellent.

 

Still has a slight bounce on that vacuum gauge though (less than 1/2 of 1" of Hg while at 18"). Might be a valve sticking? Bad plug wire? Bad plug? All I know is it isn't rock solid.

 

Check spark plug number, condition & gap.