98 Z71 Vortec 5.7

I'm new here so be gentle! I have a 98 Z71 Vortec 5.7 I just installed the 2nd new starter, a new battery, cleaned all the connections and it still doesnt want to turn over worth a flip when it is hot. It cranks like new when cold though. It started this about a year ago, I'm not a newbie to wrenching at all, but my little "huntin" truck has eaten my lunch! any ideas/suggestions would really be appreciated.

I'm new here so be gentle! I have a 98 Z71 Vortec 5.7 I just installed the 2nd new starter, a new battery, cleaned all the connections and it still doesnt want to turn over worth a flip when it is hot. It cranks like new when cold though. It started this about a year ago, I'm not a newbie to wrenching at all, but my little "huntin" truck has eaten my lunch! any ideas/suggestions would really be appreciated.

Brand new or rebuilt or used?
IF BATTERY IS GOOD AND UP TO FULL VOLTAGE AND CABELS GOOD.

Slow turn over hot is starter pulling to many amps or dragging.

Is charging system and battery up to par?

HAVE YOU CHECKED AMP DRAW ON STARTER WHEN HOT?

Both starters have been brand new, the cables are good, the battery has load tested great twice. The Alternator is charging fine. its almost like a vapor lock, or a timing issue. the thing that throws me is how well it starts when it has cooled off just a little. It starts before you can let off of the key. but drive it around town for a half hour, shut it off and it struggles to turn over about 3 rounds and then cranks. its the same nearly every time. 3 sloooow revolutions and it starts. lately though it has started not wanting to turn over at all on the first try when it has been driven for an hour or so in the heat. Its got me baffled!

Busted Distributor Gear Tooth.

Both starters have been brand new, the cables are good, the battery has load tested great twice. The Alternator is charging fine. its almost like a vapor lock, or a timing issue. the thing that throws me is how well it starts when it has cooled off just a little. It starts before you can let off of the key. but drive it around town for a half hour, shut it off and it struggles to turn over about 3 rounds and then cranks. its the same nearly every time. 3 sloooow revolutions and it starts. lately though it has started not wanting to turn over at all on the first try when it has been driven for an hour or so in the heat. Its got me baffled!

check the clearance between the flywheel and the starter drive teeth ..need 1/8 inch ...It is possible the heat is changing this ..

while your doing this ,,,check the flywheel for damage as when the starter teeth are too close you will see the effect on the flywheel teeth...

have you checked for clogged cats. or a worn cam. both will make back pressure when the truck is hot.

I did check for chewed up teeth and shavings on the starter I just took off but it looked like it was meshing correctly. I have been leaning towards a timing issue but I thought a broken tooth on the dist gear would be a pain hot or cold? I do know of several local trucks 97,98 models that have had the distributors creep on them for some strange reason, but again What would hot or cold have to do with it? I have read a lot of threads here concerning timing but they all seem to revolve around the trucks spinning and not starting, or running bad when they do. If mine makes two or three rounds it starts and runs great! I was hoping that there was some little something that was going on that was common to these trucks.

Dist does not control timing on them.

If starter is dragging hot and starts good cold.

Run a starter amp draw test on it first thing and check battery with a load tester and amp out put and cables ground and positive.

How many amps is starter pulling when hot and cold?

I did check for chewed up teeth and shavings on the starter I just took off but it looked like it was meshing correctly. I have been leaning towards a timing issue but I thought a broken tooth on the dist gear would be a pain hot or cold? I do know of several local trucks 97,98 models that have had the distributors creep on them for some strange reason, but again What would hot or cold have to do with it? I have read a lot of threads here concerning timing but they all seem to revolve around the trucks spinning and not starting, or running bad when they do. If mine makes two or three rounds it starts and runs great! I was hoping that there was some little something that was going on that was common to these trucks.

since the gap of the flywheel/starter gear is correct , this would be in most cases with a new starter/battery a cable issue...as mentioned the current flow to the starter should be checked to see if it draws less current when hot ..this would mean a bad wire/connector issue which is common on these older vehicles...also using a voltmeter when hot disable the ignition and crank the engine to see if at the starter you get a good 10volts or more..at the big lug..

could be the battery connectors pos/neg ground connections etc...

Headed out now to get it hot and test the starter for amp draw. I am also going to replace the cables altogether. It still has the original side post cables on it, so there may be a bad place that I cant see. I remember now a work truck I have, having a badly corroded spot inside the sheathing on one of the cables about a foot away from the battery connection.No way to tell it until we took it off. I really appreciate the help and will let you know what I come up with.