POWER NOT THE ANSWER

[Typrus]

I never had any challenge with the secondary opening under load. It IS a vacuum secondary. No matter how far you open the primary, it will not open the secondary except under load. As long as your vacuum system is working properly (or you eliminate the unneccessary bits to reduce vacuum leaks allowing the internal circuit better function) then it should work without a hitch. Just that the stinkin emissions circuit in the carb has a lot of vacuum loss as it gets older so it tends to bleed down.