Starter Heat Soak ?

So my SD220 is starting great now when cold. 6V. After I take it for a spin and get to full temperature and turn it off it will not turn over or it turns very slow. From what I've been reading it's likely either ground, timing or starter heat soak.

I don't see how it could be my grounding. All grounding locations are good bare metal. I've run new 2/0 battery cables and kept them as short as possible. Battery ground cable going to starter bolt. I have a braided ground strap from cab to head bolt. And a heavy cable from front of block to frame. All connections tight. Am I missing something here?

Timing - I messed with timing last night. I have it about as retarded as possible without backfiring and that didn't help.

Starter heat soak. Starter was rebuilt and worked well before I had engine rebuilt and started having this starting issue. I'm thinking heat soak could be the hot start issue. Have any of you had this problem with your old binder? I can barely touch the starter it's that hot. Before the rebuild I had a 160 thermostat in and now I put in a 180. I've read about mounting a remote solenoid. What's the opinion on something like that?

One thing I noticed is that my generator doesn't seem to be charging once the engine gets hot. On a cold start a blip of the throttle the ammeter gauge shoots up real good and the start of the drive it's showing as charging. As the engine gets hotter the ammeter shows very little charge if any at all. Initially this made me think grounding, but like I said I'm not sure what else I can do for the ground. I have the heaviest/shortest cables I can get. Does the generator know when to charge or should it be showing as charging at all times on the ammeter? Can anything other than ground cause the generator to not show charge all the time if that's what it's supposed to be doing? Generator was also rebuilt.

Any input here is appreciated. My thoughts for next step are starter heat shield and/or remote solenoid to see if that helps. Am I missing any other likely possibilities on these old trucks that would cause this?

Correct me if I'm wrong, but this is the same engine that was "tight" after rebuild and the shop said It is fine"?
With 00 gauge cable to the starter for hot and ground it should carry enough current to crank it. If that is true, we can rule out starter cables, if they are new and good, and connections as you said they are clean and bright. I'd still run my hands over the connection after a failed hot start to feel for heat, a hot connection has high resistance.
Remember, it is your eyes and your description, we can't see what your don't.
Another possibility was 12 volt field coils were used when the starter was rebuilt. no way to know from this point if that was true, or someone installed a 12 volt starter in the past and it was rebuilt as a 12 volt unit. Run the Delco number on the starter or look for the tag it should be black and say 6 volt. !2 volt should be red and say 12 volt.
Battery should a group 2 or larger.
Ammeters are not volt meters. They show current supplied to or drawn from the battery. When the truck is started a large draw was placed on the battery, the generator needs to replace that, so once running the ammeter shows a charge. Once the current used has been replaced the current should drop to near zero, none going in, none coming out.
The generator voltage regulator contains both a current regulator and a voltage regulator. The current regulator is there to limit the current the generator puts out to a safe level for the windings and commutator, it is set to the current rating of the generator. The voltage regulator portion sets the charge voltage. Since a fully charged lead acid battery has a static voltage of 2.2 volts per cell, a "6 volt" battery is really a 6.6 volt battery and needs a charge voltage over that. You want the charge voltage to be 6.8- 7.2 volts for a fully charged battery. In other words you set the voltage once the battery has been charged, not right after it has had a load on it. The current regulator must be set with the system under load.
So getting back to your problem, there are several possibilities.
One, the engine is tight, and as parts expand as the engine heats up, gets tighter. To check try and rotate the engine by hand on the fan or with a wrench when the engine is hot and will not start. If it is real hard to turn, this is your problem, despite you shops saying it isn't.
Two, it has a 12 volt starter or 12 volt field coils in the starter.
Three, the starter has a mechanical problem and binds when it gets hot, look at the armature bushings and add oil to the oil cups if it has any Remove the starter hot, and see how hard it is to turn the shaft.
Four, wrong pistons/ too high compression when hot, take a compression reading on a hot engine.
Five weak battery, replace or load test.
Six low charging voltage leading to a cronicly undercharged battery, re set volt regulator

Yes this is the "tight" engine. After pull starting and running it the "tightness" cut down significantly, probably about half. I will look into your other things mentioned. When I had the starter rebuilt I told them it was for a 6 volt. Are you saying I may have to make an adjustment to my voltage regulator? I installed a new one of those last year. I've had the battery load tested at 2 different places and it tests good.

There are different sizes of 6 volt batteries just as with 12 volt, I wouldn't expect a Toyota battery to crank my semi, so what battery group size do you have?
With the engine having been run a while and the ammeter showing near 0 with the engine running at idle or at speed, take a voltage reading at the battery, you want to see between 6.8 and 7.2 volts.
The voltage regulators are electro-mechanical and by adjusting spring tension on the correct regulator, you can increase or decrease voltage, current or cut-out settings.

This could be any mentioned above. I recall when I had my starter rebuilt, it took him some time to get a 6 armature $$$, I said go for it. I did the cable thing from my old gas drive welder with I had sold. Big battery 1100 CCA.
On an note, I never used one of these, one of the guys with a turbo used a starter blanket. I know how much heat is made with a turbo. Here is a link, sounds like it worked.
viewtopic.php?f=8&t=7085&p=52881&hilit=blanket#p52881

A group 1 is like a VW bug battery
A Group 2 is for small trucks, should be the minimum for a 220
A group 4 is 1000 CCA and if you can fit it should be more than enough to crank up to 450 cid 6 volts.

Let's deal with volts and amps and such for a moment. Is there someone near you with a Sun VAT-40 or similar tester?

Here's why I ask: On one foreign car I owned with a 1.5 liter 4-cylinder, the 12V starter was rated at 1.2 kW. Since we know that volts x amps = watts, at 12 volts, that starter was rated at 100 amps.

For 6 volts to achieve that same amount of work, it would take 200 amps.

Now, your 00 cables are [theoretically] capable of handling that load.

But has anyone ever actually tested how many amps you're drawing when trying to do a hot-start?

I believe that would be good diagnostic information to know. If your starter has excessive [electrical] resistance, or if your engine is still tight enough when hot to increase cranking [mechanical] resistance, or if your battery simply doesn't have enough "juice" when hot...those are things that are **** near impossible to diagnose via long-distance.

This could be any mentioned above. I recall when I had my starter rebuilt, it took him some time to get a 6 armature $$$,

I could be wrong, but I believe the armatures are the same for 6 and 12 volt, the field coils are not. The field coils are what limit the current flow, at stand still the armature is as close to a dead short as you can get.
I know on larger diesel starters, the armature is the same for 12 and 24 volt, but the field coil and the solenoid contacts are different for 24 and above than 12 volt. Silver contacts on the higher voltage and more resistance in the field winding.

I have no idea.

So, I did not see this post on 8/8/2020. Did this happen in 4 days?
viewtopic.php?f=8&t=10792