Hi, I am going to be building a Cox Black Widow III. I've been looking at Cox International and I found a crankcase that I would like to use. My dad told me to be careful because come crankcases could mess up the engine. long story short, I want to buy this crankcase (Below left) and do this basically. (Below right) Would it be okay to do this.

Yes you can use that crankcase to make a customized Cox engine.  Folks have been mixing and matching Cox engine parts since just about when they first started selling more than one type of engine. For performance though, some people have stated that the CNC machined crankcase is better than the cast crankcase. But the different color crankcases they have available for Cox engines does let one come up with some pretty neat looking engines though.

In the OLD days when Cox was Cox, the engines were assembled in a climate controlled room. Everything was matched. Today's engines are not matched and parts will interchange much better. But will never run as well as the oldies.

Run a "TD" cylinder and head. Run lots of Nitro. Use fuel with at least 20% oil, part castor. You can buy pure castor oil and add it to lower oil content fuels. If you're very careful, you can drill the carb venturi out a bit. Have fun!

AV8TOR

Thank you guys so much, I am really looking forward to making this engine now. Y'all have been so much help!

Have fun man. That's what it's all about! Post pics and let us know how it turns out.

AV8TOR