ok--it has just headers on it right now,i put the rebuilt eldelbrock 1406 on it and a new battery---it starts and seems to run fine while idling--i turn it off and then try to crank after it warms up---it may crank, but most of the time it acts like it starts to crank and then grabs almost like something is stopping the motor?----after a few times of this it may crank or i may have to wait awhile and then it will crank(idles fine after that)--if i keep trying too long ,the ground wire from the firewall to the body will get so hot that it will start smoking----may be 2 seperate things?---any help would be appreciated---thanks

 

Old tired battery cables,tired weak battery,weak starter,heat sinking into starter from headers,could be any of the above.
Even light corrosion on either end of the battery cables or battery terminals could be the culprit so I'd start there first with a good cleaning.
Headers heating up starter motors is a common problem,wrapping the headers and or adding a heat shield to the starter can help a lot.

 

Or it might just be a bad solenoid on the starter. Not unusual for Chevy starters to crank slow when the solenoid contacts get bad, and especially when they warm up. If you keep using it that way it will eventually take out the starter too.
Used to be able to pull the solenoid and open it up, then loosen the battery terminal and flip it 180 degrees to new surface, but I think they started making them so you can't now. Now it's replace, not rebuild the solenoid.

 

Yup,went the way of OEM reusable air and oil filters,rebuildable fuel pumps,waterpumps,voltage regulators,vacuum advance units etc.

 

OK--all cables and battery are new--the starter makes sense because the headers are hanging and blowing right beside the starter and it seems to crank fine once allowed to cool down and it sits and idles fine--did also notice alot of black soot in the headers--could be from before,will clean them out alittle and check----why would the ground between the firewall and motor get so hot that it would start smoking?--not enough ground from battery?I have it fastened to the inside of the fenderwell,but it has paint there so maybe not good ground there--just grasping,so i took jumper cables and went from battery to motor,still the starting problem when hot but still not sure about the ground between firewall getting hot yet-----hate to go on forever,but also was wondering if the timing could cause this?----thanks

 

Not quite following you here,are you saying your battery is grounded to the fenderwell?
If so that's not good,it should go to the engine block or something that substantial not a thin piece of sheet metal.
That could be the source of both your problems.

 

Whoa! Now I think Y2K is onto the real problem. The battery and starter are trying to connect when you crank the engine, and only make through the sheetmetal and the ground strap on the firewall. Move your battery neg. side to a good bolt on the block and all will be well!

 

I do think that is the problem with the small wire between the firewall now,but it had been like that forever,i just changed the fenders and put new wires were the old one was--but i will fix that,but still dont think that is the cranking problem when hot because i had the jumper cable going from battery to motor and it still does the no crank when hot---guy i know told me that the timing was too high?--sound right?---i still kinda lean toward the starter getting too hot---thanks

 

Timing advanced too far will make it crank slow but it would do it even with a cold engine.
Cylinders try to fire before they should fighting against the starter.
I'm not sure a jumper added for a ground would be a good substitute for a properly grounded system,get that fixed before you do anything else.

 

It is possible that the years of having the battery connected in the wrong location has caused a high resistance issue that damaged the starter. If you move it to the block and it still doesn't crank well when warm you may need a new starter, or starter and solenoid.