Cooling Head question

[Rolex]

Who knows the difference between the Savage X F4.6 and the K4.6, and how would I know which one I have?
I've already spent over $20 in postage sending back heads that I'm told will fit.

This is now the one I'm wondering about, but I don't want to lay out any more return postage.

http://www.2coolrc.com/images/6boltsmalls.jpg

Nova F4.6
Nova Racing
Nova Savage X F4.6 Cooling Head
HPI Savage X F4.6 (.28) (Note: Does not Fit Original Savage X 4.1 or Savage K4.6 Engine)
$43.95

 

[Candyman]

I know the original K4.6 has a silver crankcase. As best I can tell, the F4.6 has a black crankcase. Also, the F4.6 head is perfectly round. The head on the K4.6 and K4.6 HO has these sorta flat parts milled down the head.

 

[Rolex]

Great info, Candyman.
Mine had the black block and the round head, so I'll go back to my search.