Slow cranking when trying to start

[elky70]

I have a 79 K5 blazer with a 396 crate motor from blueprint. I have a brand new battery, I’m on my third new starter from Napa. When I go to start it, it seems like there isn’t enough power getting to the starter. When I try to start it using a remote starter switch (by passing the ignition) it seems to have about 10-15% power but is still cranking over very slowly, once it finally starts to turn over. My question is: is this another faulty starter? Or is there something wrong with my ignition wiring? Did I possibly lose a ground wire on the ignition switch or is it it something else to do with the ignition switch? Been trying to solve this problem for months and months. New batteries, new starters, good grounds from the starter, battery and engine block. What am I missing? I have not swapped out the ignition switch or got up under the dash to trace it out. It worked great for a few months, then it didn’t. Putting a new starter and it worked good again. Then replaced the battery after it went dead trying to start it one day. That day it seemed like it was drawing a lot of power and I ended up finding one of my ground wires to the frame had heated up. It was too thin of a wire that the previous owner used.
That’s what I know. Any help would be greatly appreciated. Will compensate the person that helps me figure this out.
Thanks for reading.

 

[legopnuematic]

Where do your ground wires from the battery go? To the frame? Engine block? Alternator bracket?

 

[Sad Sack]

Recheck all grounds (battery to body, battery to frame, battery to engine and whatever other ground point those models have) and use proper 4-gauge battery cabling, copper straps, fresh metal contacts - no shortcuts.
Replace the positive battery cable with a new 4-gauge cable (no cheap CCA crap). Use a battery around 850 CCA.
Research say a 4hp hi-torque performance starter. You are more than likely pushing over 10 to 1 compression on that 396 and you're going to need good clean energy to turn it over.