Slow hot crank

[Jppr26]

So I need some help, truck is a stock 87' custom deluxe with a 350, and when it cold it cranks hard and fast, takes about 3 seconds to fire but is running fine.

When it's hot, it cranks like the batery is about dead, but fires up.

Truck has a manual transmission, stock exhaust for now, new battery, alternator, starter w/heat shield. The truck did this with the last starter as well

 

[chengny]

So I need some help, truck is a stock 87' custom deluxe with a 350, and when it cold it cranks hard and fast, takes about 3 seconds to fire but is running fine.

When it's hot, it cranks like the batery is about dead, but fires up.

Truck has a manual transmission, stock exhaust for now, new battery, alternator, starter w/heat shield. The truck did this with the last starter as well

This condition is often the result of overly advanced timing. It can get so bad that you get kickback while cranking and run-on after shut down. Try retarding the timing a bit. Rotate the distributor CW in tiny increments and see if it alleviates the issue.

 

[Jppr26]

This condition is often the result of overly advanced timing. It can get so bad that you get kickback while cranking and run-on after shut down. Try retarding the timing a bit. Rotate the distributor CW in tiny increments and see if it alleviates the issue.

Timing is set to 0 per the factory sticker under the hood with the esc wire unplugged

 

[chengny]

Timing is set to 0 per the factory sticker under the hood with the esc wire unplugged

Sorry missed the year - and, yeah with EST there's not a lot you can do with timing. Just break the TAN/BLK lead and set timing as per the sticker.

Maybe it has to do with heat under the hood causing a reduction in current carrying capacity somewhere in the starter motor circuit. You might consider installing a new set of battery cables - sounds like you've covered most everything else. There isn't much involved in the starter motor circuit. As long as you have a good power supply from the battery positive to the solenoid, a known good starter/solenoid and a good ground path from the engine back to the battery negative...a 350 should spin right over.

When it's hot - and you get a slow crank - does it run well after it fires up?

 

[Waylon]

I had the same issue with a 79 GMC with a stout 350 and headers. I assumed it was a heat issue so I built a heat shield over the starter. That didn't work so I added an external solenoid on the fender well. I also added new double ground cables from the battery, one to the frame and one to the engine. None of that helped. What it wound up being was the positive cable. The cable physically looked like new. I guess it had corrosion somewhere I couldn't see. So, I did a lot of work and spent some cash on stuff I didn't need just to find out it was as easy and simple as a positive cable.

 

[bucket]

Don't overlook the basics. That's also the sign of a junk battery. An old style charging system tester is helpful here. The kind that puts an actual load on the system, rather than the new type that just puts a tiny load on the system and then gives you a reading based off of a calculation.

 

[Jppr26]

I haven't spent alot of time on the cables, walks thinking maybe a heat issue, but my ground cable is about 2 feet long, just what was on the truck when I got it.
I'll check the battery cables that may be the culprit, just wanted to get some ideas of other issues to check