I have just finished putting the top end of the engine on (400 CI HO 68)
I put a new msd dist,accel coil,wires,holly street avenger carb,ederbrock intake,etc...
I set the timing by ear and the engine was running fine for about 20 min then it just stopped running like no fuel or elect problem.
It seemed when the engine or something got hot it quit.I was told that when I hooked the accel 4200 coil up, I ran 12 volts straight to it from my ignition and I need a regulater to lower the volts down to 8.5;is this true that my coil heated up and quit?
Do I need to put an inline voltage regulator in to lower the voltage?
I also put a 192 degree thermastat in it ,is that to hot?What temp thermo should i run in this engine?
The fuel pump seemed to be working fine but I will put the new one in I bought just in case.
Is there anything I can check for this problem? thanks for your time.  

You said MSD distributor, is it full electronic or is it still a point's distributor?  Using a different brand coil from distibutor isn't necessarily a problem but are they matched up?  Is that coil designed for a points or electronic ignition distributor?  If the coil is designed for a point's distributor and you have a full 12V running to it then you will burn the coil up.  Factory '68 coil power wire is about 8.5V so unless you modified it that's what it should have.  If it is unmodified and you hooked an electronic distributor and coil to it then it would run alright, but as it got hotter it wouldn't have the power to keep up with the ignition.  And if my electrical knowledge is right, for a 12V system to make the same power at 8.5V it would need to draw more AMPs which would tend to heat things up.  If the coil and distributor are mis-matched I'm not sure what the results would be.  

The 192*F thermostat should be fine unless the engine pings, if it does then I'd progressively step it down. (make sure timing is right where it should be first so you know it shouldn't be pinging from the timing being too advanced)  

Pretty much have the same thoughts as SilverBuick.  

I guess one more piece of information that would be useful is how did it die?  Did it sputter, choke, and then die?  Or was it like turning the key off?  Did it start running different at any point during the 20 minutes?  Another piece that would be useful...does it start now?  

True, after all I did run out of gas while doing a cam break in   and didn't believe it.  

TheSilverBuick:
True, after all I did run out of gas while doing a cam break in   and didn't believe it.

LOL...me too.