starter issues

so I have problems with my starter on my BB402. I replaced the starter with one I got from autozone (maybe my first mistake) and have the same issues I had before.
So here goes with my best description:
If I ever have to hang on the starter a little longer than normal (like if my float bowls dry out and I need to prime the carb by driving the fuel pump) it seems to be permanently affected for a day or so. And when I say I hang on the starter longer than normal I just mean if I crank it for about 5 seconds or so, which feels like a really long time but really just around 5 seconds.
Contrary to say 1-2 seconds when everything fires up good.

So after this the next time I go to start it the starter will kind of clunk at first and then take a second or so before struggling to crank the motor, and then it usually eventually gets it cranking but it sounds sluggish and cranks slow so it's hard to start.
Basically it makes me afraid to take it out because I feel like it won't start. It always does but sometimes I feel like it's by the skin of my teeth.

Does this sound like a 'cheapo' starter motor issue and I should not have bought one from autozone?
If I need to find a good quality one I'd be more than willing to spend more money, but I just don't know if that's the issue.
I know I don't have battery issues/charging issues and I leave a trickle charger on it all the time too since it sits sometimes for weeks.
My voltage when the engine is running is always right around 14, it drops lower as more things are turned on but I think that's normal.

IMO buy a OEM starter. You might want to check your grounds Battery to frame battery to engine battery to body. But it really sounds like starter.

I agree with what has been said though I wonder about the size and length of your battery cables. If they are smaller than 4 gauge I would seriously consider making some new ones out of welding cable.

Times 2 on the wire gauge. If you cannot make your own you can buy "0" or double"00" cables - you'll just need to know the length required.

Also, how much initial timing is in it? Is it like 12 or 14 degrees? Is the initial crank the hurdle? It sounds like it wants to bust off at the hit of the key.

I'm not sure of the cable gauge, I'll check that though.
my initial timing is probably something like 12 or 14, and I also use a vacuum advance that takes it up to a solid 35 at idle, the motor won't idle well without that vacuum advance.

but in general when the carb is primed fully it will fire within a second of cranking.
I just ran it today and after sitting all week it cranked like normal again.

so it is 4 gauge
and in my truck the battery is under the passenger floor pan, so it's a pretty short wire run to the starter also
my ground is solid right to the frame 3 inches away, and I have numerous additional ground straps linking the engine to the frame as well.

I really feel like it's a starter quality issue by the way it reacts.
so my next question is, which might be dumb, how do I tell for sure on a site like summit which starter will work?
when I go on there it has options for numerous generations of big block and I'm just not sure which mine is.
It was out of a 71 chevelle and it is a 402.
all the searching I do yields all kinds of info about different vehicles and years and I just can't zero in with confidence. Unfortunately I don't think I'll be able to see a casting number in the truck as tight as it is, but I could probably search through my notebooks from when I built it and find it written down somewhere if that's the only way. I'd prefer not to do that as I built it initially 15 years ago and I've moved twice since then so it will be a long search for my old books.

I'm just worried because in the past I've put starters in it that would not engage the flywheel at all, the nose would just pop out and spin like crazy in air, and not even grind slightly. . . ..zero contact.

What do you have against buying a new starter from GM. Quit trusting the other guys.

no I don't have an issue.
but do you mean chevy dealer parts departments will still provide those parts?

I've had great luck with summit brand hi torque starters. They have a great return policy.

Pull your starter and take the solenoid off. Then take the starter apart and clean everything and replace the brushes, they're probably close to being worn out anyway. Next replace the bendix and be careful to not loose any shims on either end of the armature. Take some fine emery cloth to the commutator cleaning it till it shines. Put it all back together with a new quality solenoid and you should be good for many years.

https://www.ebay.com/itm/NOS-GM-1906...cAAOSwav5aqBS7

https://www.ebay.com/itm/New-OEM-Del...rd!65807!US!-1

https://www.ebay.com/itm/1957-77-GM-...kAAOSwLw1ba0yd

quick update, I bought a multimeter because thus far the only thing I've been judging my voltage on was my gauge inside the car, which doesn't have the greatest resolution.
while running with no power items on inside the car I'm getting 13.5 at best, fluctuates basically from 13 to 13.5

I know 14.5 is kind of best case.
Does this sound like an issue to anyone or still reasonable to get 13.5?

At how many rpm? It's usually best to measure the output while above idle, 1500 to 2000 rpm. Then you need 13.8 to 14.2 volts,

Are you using NEW STARTER bolts with the knurled section?????? standard shank bolts will cause problems because the starter isn't lined up and will move around--

What type of alternator are you using? If it's a '70s style alternator, 13.5 volts is normal. In 1988 and newer, they increased the voltage to about 13.8 to 14.5 volts.