383 stroker elderbrock 800 cfm carb, mechanical fuel pump, rpm air gap intake, rpm heads ported to match intake, all new parts, motor was bought as a turn key crate motor and runs perferct at idleand revs fine in park. when put under a load, the carb starts to bust up bad, the carb was tuned for this motor. figured it was running to lean, try to richin it up and dropped three plugs. new plugs and cant get the carb close enough to start the car so we can tune it, maybe power valve any opinions?

The Edelbrock carbs don't have a power valve. They use spring loaded pistons to control the enrichment of the mixture at low vacuum. You might try lighter springs under the piston. What happens to your timing when you put the tranny in drive? How much does the rpm drop when you drop it into gear? Is your converter compatible with the engine?

Sounds like timing to me too.

i havent done anything with the timing, it is still at 12 dergrees, maybe a vacum leak. i dont know really starting to bother me

Make sure the floats didn't get banged around. Those carbs are very sensitive to float levels.