Tried a lot no fix. Tried timing. New dist, plugs, wires, dis cap, rotor. Carb is a edelbrock. Not sure on specs. It's cranks fine cold. Tried also new battery cables. It has new battery, starter and starter solenoid. Could the crank bearings be worn? And when it's warm the clearances are too much it binds? Not sure what else to do.

 

Usually, a slow crank when warm, but cranks fine cold, is timing or weak starting system related. I see you have done all the usual suspects.
How large are the cables? How clean are the hookup points?

FWIW, a "new" starter does not mean it is *good*. Particularly if it's a reman unit from a parts store........

 

It's a ac delco starter. Been through plenty of starters. All the same. Wires are 4 gauge. Clean hookup points everywhere. I'm just not understanding the slow crank. It's fine cold. Also has a new 850 cca battery. I can set back the timing and it's not as bad but then I get a bucking at higher rpm. I got it set at 10 btdc. Or whatever is recommended. Should I try a higher octane fuel? Maybe it's detonating or something.

 

Have you tried a heat shield on the starter?
Windings get very resistive when they are hot.

Are you running headers?

 

+1

Either the timing is just too much, the DS2 "start retard" circuit is bad (or not even there) or the starter just gets too hot.

 

Timing is to spec. No headers. Haven't tried a heat shield. Where do I get one? How do I know if the spark retard is working? It is hooked up.

 

Heat shield is something you might have to make yourself.
As for the start retard circuit, Motorcraft module or some cheapo replacement? most non-motorcraft boxes don't have it.....

 

Says motor craft on it. Can I get that wrap stuff?

 

You can even cut apart a shiny juice can to use for diagnosis.

 

Ok I'll try that.

 

Yeh, on the right track, Starter gets hot, Windings "expand" = much more resistance = slow crank. cools down, contracts, spins like a bi$%.
I found a 12v computer fan, set up with a thermostat kept mine "cool enough" where issue was greatly reduced

 

Make sure you have 12v on the white wire going to the module when cranking the engine. This white wire will be fed by a red/blue wire. This is the spark retard wire.

 

Sounds to me that the issue may be more along the lines of a binding pulley. When cold, bearings and mating surfaces are contracted and smaller. When heated, bearings and mated surfaces are expanded, therefore causing a bind. A good way to test this out is to get the truck to operating temp, turn off, try to start to verify discrepancy is preresent,remove the serpentine belt and try to crank. If the vehicle starts like it should, without the slow, heavy rotation ,you know there's a pulley bound up. If not, looks like a possible starter, or even a corroded wire decreasing current flow.

 

Ok, everyone has different ideas and theories of what could be wrong. If you want to verify if it's a timing problem, put a switch on the coil + wire. When it cranks slow, turn the switch off or pull the wire to the coil off. If it cranks fast with the coil disconnected, then timing is your problem.

 

A clamp on ammeter will tell you right away how much the starter is drawing.
Disconnecting the coil is the easiest way to tell if it is timing.