As the title says, I just bought a used set of C rotors and their weights are 4372.5g & 4357.2 g.
Is this normal?

The rotors, I was told, came from the same motor and appear to be in exellent condition. Both rotors, when weighed, were clean, and had nothing else but rotor bearings installed.

In the past I have had rotors with the same letter code within 1 gram of each other.

 

It is not abnormal to have a spread, I just weighed three C weight FD rotors , 2 @ 4330 and 1 @ 4340

Now yours seem to be on the higher side like a B weight, as I have D weight rotors at 4320 for example.

 

Do you think I will run into any issues runing the pair as is?

 

Depends on what you are trying to build, if you are going for high RPM, high power, then you might want to get them balanced. Ideally you want them as close as possible, that being said I have opened countless remans with A-B, B-C, C-D, etc. combos which function without issue for most typical applications.

 

Gotcha!! These will be going into a 500rwhp build but not reving reving past 8400 rpm.
Do you know of anyone successfully adding or removing small amounts of metal to the rotors just equalize weight? Without the expensive balancing equipment that is.

 

If your building this engine for 500hp, send them out to be done, honestly, don't cheapen out, you do it yourself there is slim to no chance you'll get them right

 

Well then for that level, you are mixing and matching rotors and counterweights, you really need to have the assembly balanced.

 

Thanks guys