not different from 350-400......what kinda carb you have on it and whats all done to the motor and what kinda dist. you have......does it roll-over good when hot or does it go fast then slow down a little then fast again.......

have you checked the starter on it ?

How many batteries, what CCA, and what gauge and length battery cables?

Check the firing order to make sure its wired correctly.

Of all the 400s I have ran, one thing is common; they all run hot hot hot and the crank /rods swell. That may be your hard turning issue when it is warm. The engine my need rebuilt . Check the timing chain as well, it may be stetched. The old link chains were known for it. I usually  ran a good high grade oil, with slick 50 or Prolong. It seemed to help. Get the beggest dam radiator you can shoe horn into the car and a good electric fan, so it will be pulling in air no matter how fast the engine is turning. Pro mods are heavy so you have alot of work on that engine out there  anyway, besides the ramjammin around and pushing other cars around. That is what I would try.  

I tried to tell you on the old wecrash.....it's the starter,when it gets hot,it gets weak......how many new parts have you bought before?

new parts only mean their new,it does not mean their good.....the more new parts you buy,the more you will find this out!

400`S DO NOT "RUN HOT" THATS A MYTH. IF THEY ARE SUCH JUNK WHY DID CHEVROLET BUILD MILLIONS AND MILLIONS OF THEM FROM 1970 THRU EVEN THE LATE 80`S?  YOU HAVE OTHER ISSUES BESIDES THAT ITS A 400. BUY A GOOD STARTER, STOP PUTTING BAND AIDS ON THE ISSUE. MAKE SURE YOUR HEI IS FUNCTIOING CORRECTLY, CHECK FOR YOUR CAP/COIL GROUND, REPLACE THE MODULE.... AND BUY A 1000 CCA BATTERY AND RUN HUGE BATTERY CABLES........

Id definately try a different Distributor then. You chould check the timing chain by taking the distributor cap off and turning the crank backwards and forwards with a big ratchet or by hand, and see how much delay there is in the movement of the rotor button.

i had a freind running a chevy 350 ran great at first then when it got hot it wouldnt start it turned over real slow and everything we changed the distributor and it ran great.How much does one of these gear reducted starter actually do never have used one always wondered? and where could you find one at?

Ebay, Summit, Jegs, GM dealer, or Speedway motors.

Try this,  get motor hot, not stupid hot but hot enough that you know it will be hard starting.  now crank motor over WITHOUT igniton on. If it still turns over hard, its NOT timing or distributor problems. the 400 cylinders are  ''siamese'', meaning there is no room for water between them. they have what is called a ''steam hole'' in the heads that allows water to flow thru.  Some mechanics believe these hole are useless and other believe they are helpfull. I believe one of these holes getting plugged can cause a cylinder to get hotter than others.  IMO you may need to check for water flow thru these steam holes.

Not related to the hard start condition but as far as the steam holes go...there are 2 between each pair of cylinders. One below and 1 above...common sense told me before he died (see joke thread) the one below each pair would let pockets of air and steam escape...the one above I can't see a good purpose for.

As far as the hard start goes I have always had my ignition setup on a seperate switch so I could get one spinning then hit the ignition..really hot or not it helps if you run alot of advance as the starter isn't fighting the spark to get the damn thing running.

i dont mean to brag or anything but i got a 350 that i rebuild last year and used hyperteptic pistons in it and i got it up to 250ish degrees and it started like 3 seconds of turning over, it turned over not fast but normal maybe a tad slower, now is this just getting lucky or do the rebuild and pistons help?