What is the purpose of the spark delay valve these cars came with? I've never run one on my Maverick, but I'm curious.
I believe it had to do with emissions only, Larry. The reg's back then had more to do with Nox than raw unburned fuel going out the exhaust pipe. Still that way today although preheated o2 sensors and more efficient cat's have cured some of the nasty side affects caused from heavy ignition lead. Kinda silly really considering why these smaller cars were even designed in the first place. lol The problem with reduced spark lead is increased engine and exhaust heat saturation. Then from there we get into reduced manifold vacuum and reduced torque production below peak torque.. especially idle and off idle/cruise speeds. This is the main reason why I strongly advocate manifold sourced vac advance over ported/timed sources. Biggest problems with that are considerably higher Nox production and the carbs tendency to run out of fuel in the idle and transition circuits which leads to lean surge or popping/backfiring issues that most "bolt on builders" don't know how to effectively deal with. Oops.. "power on the brain" made me forget to mention the quicker warmup times associated with the vac delay valve. Usually tied into a coolant temp sensor so the delay valve eventually gets out of the vac pots way to let it function normally. Goes back to and revolves around the higher heat production I mentioned above. The funny thing is that it(vac delay valve) has no real direct affect at true idle speeds because they generally use a timed port for the vac advance on these types of smogger setups anyways. Kind of an oxy-moron to say the least and your choke better be working to keep all the components working together as designed. Hope that helps!
