Runs good when cool outside but runs rough when weather warms and gets hot ,its a 350 chevy motor

Does it run rough at hot idle ? How many miles ? Any recent work done on engine ?

I don't really know the answer, however, I would like to share my story with you, in case this happens to be the case with you. My older Volvo had all kinds of problems but only when warm and when it was wet outside. I had a mechanic that was throwing parts at it until my dad told me to go to an electrical specialist. He found out that the ground to the chasis of the car was not good, and in fact, when it was hot, it actually got red hot. The water aggravates electrical shorts. A bad ground is more common than most people think.

I hope that helps.

Leaking intake manifold (vacuum )

it often happens in the winter, naturally, the cold weather will have some effect on all the car's system, especially the battery and cooling system.
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Easy to get a MST-3

Sounds like fuel pump in tank is going. Should be 34 psi with engine running. If you are below that, the pump can't keep up pressure in hot weather.

water pump cud be failin--plugs wire probly hav inside wear as well as distributer-inspect--du a scan of vehicle for any codes

Could be a problem with your intake air temp sensor or your coolant temp sensor. The most likely would be the coolant temp sensor. It may be reading cold and will make it run good as the engine is cold but as it warms it is not adjusting the air fuel ration to the proper levels making it run rough hot

Hello,

I would also be compelled to suspect the lack of Fuel, towards from the Engine, normally the Carburetor combines fuel and air, into a highly volatile mixture. So when its hot, I would think it evaporates so quickly before it reaches the engine. Try to tighten any pipes, or look for leaks around the Carburetor.

You need to find oput what you loose when the truck shuts off, all you need is Air, Fuel , and spark to run one of the three are droppuig out when it stalls and will not run. Chech the carb for gas it sounds like you have a weak fuel pump.

For starters have the radiator and coolant system flushed which may help cool the engine better. But when it gets too hot, motor oil loses it's viscosity ( thickness and lubrication properties ) and gets thinner. Especially in hot weather you should make sure you have good oil and make sure you dont run it low on oil. On the flip side make sure that it's not overfilled because this will blow out the seals and you'll have much bigger problems than no power. Hope it helps!