I have an 81 K10 4.1L I've been driving as a beater and am getting ready to restore to original. It recently developed power loss under load and black smokes like a 6.2 diesel under more than half throttle. The symptoms developed suddenly while driving at 50 or so and have continued. Any help on where to start looking would be appreciated! Thanks in advance...

 

I don't know about black smoke pull your plugs and check compression see what you got. If compression is good you may have a blown gasket in either heads or intake but probably not. How many miles are on it, maybe its just really worn out and in need of a rebuild. BTW what is a 4.1? Is that supposed to be 4.3?

 

black smoke=overfueling...maybe the power valve in the carb

 

Thanks all, I'm going to take another look at her this weekend. It's got 92,000 original on it and the 4.1L is the old inline 6 with the 2 barrel on it. The truck's at my other place 80 miles away so I only get to look at it certain weekends. Thanks again for the help! I'll post back what I find.