1977 225 , 2barrel, auto, adjusted valves, new timing gear, and all wires, resistors, coils, alt, starter, etc. This engine is stock and looks like a show engine with everything replaced including carb and all attachments like choke pull off etc. It runs great when started; with power and idles good. Actually runs good for about twenty minutes (in fl) and then it starts to stumble all over the place. Will barely run. Everything has been replaced and no-one knows what is wrong. pleeeeeeeeeeeeeeeeese help. Many Thanks, John

Check for vacuum leaks. Make sure the carb is tightend down, manifold to head bolts are torqued correctly, if its a BBD check the throttle shaft for wear. Then inspect and replace any suspect vacuum lines. Easiest way ive found to hunt for vacuum leaks is to spend a little time squirting around under the hood with some WD-40. Good luck

-Aaron

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The "Silver Bullet"
87 Ram D150

Vacuum leak is a good call.
It could also be a plugged idle circuit. (yes, even in a new ot rebuilt carb.)

Here is the test, get the engine warm and to the pint where it is running bad, now remove the air cleaner and slowly close the choke flap by hand to see if the idle smooths-out, if it does, the idle circuit is running lean.
This can also be caused by a stuck PCV valve so also check that.
DD

Also check for a cracked distributer cap (it may be new, but I've seen it happen), or possibly vaper lock.

I have also problems when engine is warm up. The mixture is getting lean. I would like to know, if it is possible that coil, pickup coil or ECU is not workin properly when warmed up?

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Sorry, my english is not very good