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PackardV8 01-22-2013 08:34:48 205.188.116.19 Report to Moderator	Perhaps not that it matters in terms of repop pistons but what does the service manual say about piston installation front/rear???? Do the OEM pistons with no pin offset have any marks or notches to indicate front????? It mite be advisable to look at the oil ring groove (of OEM) to determine if there are any holes in the groove to one side or the other of the piston. As for my comment above about engine balancing i should have specified engines of FOUR or more cylinders and NOT in a radial configuration such as some airplane engines. Note that the Z120 has no counterweights. I have several V8 passenger car cranks here and V12. When placed COMPLETELY BARE on leveled knife edges the cranks will hold their position no matter how they are stopped on the knife edges. Piston and/or rod has no effect on crank balance (except 1 and 2 cylinder engines and radials). [Reply]   [No Email]
Jason S. 01-22-2013 10:46:26 174.228.64.200 Report to Moderator	Re: 134 piston direction? in reply to PackardV8, 01-22-2013 08:34:48   I"ve got a 5.0 liter Ford engine I put together and had to have it balanced. I went from stock TRW forged pistons to Mahle forged pistons. The Mahles were about 60 grams lighter per piston, but they were a matched set and weighed within one gram of each other. I even verified it because the engine builder I used at that time said as long as the Mahles each weighed the same it won"t make any difference in the balance of the motor. I put it back together and above 2200 rpm"s it would shake you out of the car. I changed flywheels, pressure plate, harmonic balancer..nothing changed it. I tore it back down and took the rotating assembly to my current machine shop. He laughed and said with that kind of weight difference of course it would vibrate. He balanced it for me and I put it back together and it is smooth as silk now. It madea believer out of me on balancing. Which OEM replacement pistons have to be within 10% of the original pistons weight or they aren"t supposed to be sold as OEM replacements. [Reply]  [No Email]