I went to look at a little truck today. It has a blow by, burns a little oil, but it is dripping down onto the drive shaft? I think and burning off, makes the truck smoke a bit. Anyway, it also is making a little noise under the hood. It is not top of the motor, but on the bottom. The rocker arms have been checked and are fine. It knocks though. Could it be a piston? This is a 1981 Nissan pick up. The guy is only asking $250 for the truck. It runs, rides smooth, drives great, but there is the noise...what are the possibilities? I need a worst case scenario of what it might cost to fix, and an estimation of whether it'd be worth it to get it, fix it up, and drive it till the wheels fall off. It's not too bad looking of a truck, minimal rust, few dents...but just hoping for it to be a knock around, hauling feed, scrap metal, aluminum cans to the recycler, goats to sale barn type truck. If I blow the motor on the way home, I can get close to what I paid back just to junk it. Soooo, what say you mechanics of BYC? Buy it and chance it? OR don't waste my time on it?