Hi! One of my friends has an 83 ford f100 with a 300 6, it seems to run rough, the number 5 hole runs about 75-80 lbs of compression, the others run 175-180, I think it needs a head gasket, but is it normal for this engine to run so much compression? It's a stick engine, never rebuilt. Thanks in advance

 

175lb is healthy but obviously the 75lb cylinder is bad. Run a wet and dry compression test to know if your rings are good. After that, run a vacuum test to know if your valves are good.

 

175 does seem a bit high. Generally, a good, healthy engine is around 150 - 160. I've heard of compression going up from carbon buildup inside the cylinders.

Definitely pour a little oil down the spark plug hole and try the compression test again. If it's the same, it's either the valves (or possibly the head gasket). If it goes way up, you know the rings are bad and it's going to need some work.