What is your initial timing set at?
like to know this and any more info also ?
i have had the same issues ,same car, two different engines, have had the seperate starter button , no change, first engine 10.5 , this current engine , 12.5 to 1 , no difference,, the 'dakota' and ebay starters the same , spin like crazy , but , as soon as any heat over 100 , it might spin fast for 2 secs , then like a dead battery ! just tried a new 850 battery same, new marine 1000 battery , same ,, i have a cable from engine to k member, starter to frame , battery to frame , battery to rear wheel housing , battery to starter for grounds including intake to firewall strap !
replaced bulkhead connector few years back, and the starter relay also i believe 7 yrs ago ?
if, according to the light, i set timing at about 20 ? it fires right up when cold, if i back it down , i get a fire in the carb !! and because the battery 'dies' in 3-4 secs, it is hard to suck the flames down !!
i am looking at something like this :
http://www.texasindustrialelectric.com/T_114_12_series_parallel_switch.asp
https://www.ebay.com/i/133326629718...l8ogANYczMqT9pD7rv0AEzJJGhaSkg1waAj_TEALw_wcB
to add a second battery OR go with a 3 post ,16 volt battery ?
as it seems when i have the charger on the battery, 12.5-12.8 really won't turn it , like it is dead ! , when it says 13.8 , it spins good !? but kills the voltage fast ! in a couple seconds or so ? (every battery i have tried ) .
so, battery setup change and/or, a powermaster type starter added to the mix ? is how i am now leaning.