Fevre

Just bought a forged 3.75 crank (383) and it is intended for 5.7" rods, my question is if I get a 6.0 rod that weighs close to the 5.7 rod can I use it? Is there more to it than just weight? I understand that usually a 6.0 rod is going to weigh more than a 5.7 but I see a varience in weights in the 5.7 so I am not sure if there are other factors are involved.

Thanks

Clink69

Not sure about the weight but you will have more clearancing to do... but in any case 6.0" is the way to go, it will rev easier...

clem zahrobsky

the rod weights more but the piston will be lighter because it will be shorter. the ratio is 2 to 1,1 gram more weight on the long rod you save 2 grams on the piston. :chevy

Fevre

So as long as I get a piston/rod combo that is close to the bob weights it should be no problem? Please correct me if I am wrong on this, I want to know what I am talking about when I go to the shop to have it balanced and tell them exactly what I want. I have not bought the rods/pistons yet but I do have a set from when my first stroker moter went :U . 5.7 rods that need resizing and 10/1 comp pistons. I think I might even be able to get the cast crank welded and reground to use in a test motor for a FI sytem.

Thanks again guys

Pete79L82

No, you can not just use the total weight of the rod. When balancing you have to use the weight of the big end of the rod and the total weight of the rod/piston/wrist pin/ring package. To supply only the total weight will get you close. If that is satisfactory to you, then it is good enough. But to do it right you must have the rods, pistons and rings that will be in the motor. Advertised weights of rods and pistons can be off as much as 10 grams which will make the effort of balancing usless if you do not have the actual parts used in the motor. You can get away with that on a low RPM motor and never have a problem but it will show up very quickly as RPM goes up.

Fevre

Pete

Sorry I left out the rings and pins in my desc, I plan on giving the shop the whole rotating assembly so they have everything to balance.