It all depends on the year and the heads on the block. Early 150's in the late 70's had compression in the 110 range. Later models of the crossflow were more like 95 ish. The 60 degree loopers were quite a bit higher. So, please help us out here with a model or year, crossflow or looper. Likely the compression may come up somewhat if the carbs are supplying fuel/oil during the cranking of the engine. Maybe a few lbs, maybe 5. That would get the 90 lbs cyls up to maybe 95. The problem will always be the 65 lb cylinder. Even at 70 lbs, it's below the normal accepted tolerance of 10% between cylinders. So, you could be looking at a teardown and overhaul to get this block back into normal running condition. So the question is: are you ready to purchase this with a potential overhaul staring you in the face.
