You say timing is good......have you TRIED more initial?
Yep. Timing is good. 16 or 17 seems to be the number.
Like crackedback always says, the engine will tell you how much it wants. If you pull initial timing up and the engine idle speed increases, it still wants more. It's not uncommon to see as much as 20* initial or more. Of course if you end up with that much, you will certainly have to limit total. Just food for thought.
Also something like this is useful too.
JEGS Performance Products 154050 Carburetor Heat Shield 4-Hole Style | eBay
One last note.......you say you don't want to go to an electric pump. Often times, what we least want is what works. A good electric pump with a proper return system will cure your problem. Even with crappy ethanol spiked gas. I would all of the above, plus the electric pump. That joker would run good sho nuff then. ..........of course, you could remain in the past and never know.
