Technical Iron / Aluminum Piston Question

Awhile back I purchased a set of NOS Iron pistons for my 48 IHC truck. I paid quite a bit for these, due to the fact they are about impossible to find. Come to find out the pistons that came out of my engine were Aluminum, which is what the factory manual says also. The manual makes no mention of Iron for any years of the truck as far as I can tell. Wondering if these will work in my engine? Will they throw off the balance? Really would like to use them if at all possible. Thanks in advance

 

Not to insult you, but you’re not confusing iron vs forged? I’m sure someone made iron pistons, I’ve just not come across them.

 

If it's a straight six engine, then the weight of the pistons doesn't really affect balance, as long as they are all the same weight as each other. The engine design is one that is naturally balanced.

btw Iron pistons were very common, Chevy had them thru 1953 in some engines

 

It is a straight six. That certainly makes sense from a balance standpoint. Thanks for the reply.

 

The engine will be smoother than any you’ve ever had if your valves and tune up are good. Make sure your machinist knows the clearance for cast iron. My dad bought a new 216 short block from Harry Mann Chevrolet for his shop truck and was by far the smoothest/quietest engine we ever had.

 

That makes me feel much better! It will be a complete rebuild. The motor sat for many years and was stuck when I got it.

 

It probably wouldn't hurt to weigh all the individual pistons/rods/etc and see how closely matched they are. Old time manufacturing methods often caused component weights to vary significantly. The idea is that the weight of one assembly counter balances the weight of the opposing assembly. That works good when all components are essentially the same weight. When they aren't fairly similar, then you can still create vibration. Aircraft engines that have opposed cylinders are known for often producing vibration. Many builders now strive to balance their components before assembly in an effort to smooth them out some. Its something that can be done easily and cheaply at home with a small digital scale.

 

Cast iron piston was the standard originally. We had to move to aluminum pistons as engine performance increased, the heavier cast iron is unsuitable for high rpm and aluminum is better at transfering heat. I'm guessing suitable aluminum alloys had to be developed too, to handle wear, have a suitable thermal expansion and so on.