Hi guys, I am putting a 305 together in a pinch. It needed pistons, and I have a set of pistons and rods ready to go but they are around 30 grams heavier than stock (for the entire rod/piston/pin/rings assembly). These replacement pistons are actually used std bore 305 pistons from a 1983 engine. They are going in a 1987 TPI engine. I know I will lose half a point of compression but I don't care at this point. Would the 1983 engine with the heavier pistons have had the crank balanced differently from the 1987 engine with the lighter pistons? I am pressed for time and this engine will see low rpm daily driver type use only, so I am tempted to just use the slightly heavier pistons. The heavier pistons are within a few grams of each other for the set of 8, but heavier than the correct ones for this 305 engine. Balancing the rotating assembly is absolutely not an option, I could get a set of the correct pistons for much cheaper, but I'd rather use these since I already have them.

 

If the crank were balanced to the reciprocating mass as an assembly, it would be balanced differently. In a street engine, it might not matter. Is a used 350 crank an option?