When doing the timing belt and replacing the sprocket seals, is it necessary to drain engineoil?

 

Necessary? No...

 

...but probably a good idea? wouldn't the oil spill out???

 

For the timing belt change, no, it'd not spill out... And while I am not sure about which "sproket seals" you are reffering to, the oil stays in the oil pan and shouldn't spill out if any work is done above its level. But, since you are at it and getting dirty, if it at all needs the change, well, then do it!

 

thanks for the reply,

I speak of the engine oil seals, cam, layshaft, crank.