Is it advisable to install one on an A series motor or can I install a small filter onto the tappet cover instead?
Thanks Matty

It depends if you race the car or not.

Generally, I don't think you need a catch can.. except on Turbo'd cars, or full-on race cars, like the ones that used to do 13,000rpm down conrod straight with the A12.

I've never seen oil in the filter unit of a standard A12. This means that no oil comes out of the valve cover breather. So I'd try my best to adhere to environmental laws, and I'd pipe the valve cover breather back to the airbox. If you run webers with socks, instead of a box, then a small filter is fine.

Chris

A small filter is fine and shouldn't affect emissions output (though it might be against the emissions law where you are). Just make sure your PCV valve is connected

If your street engine is heavily worn, you'll get oil in the filter but otherwise it should be OK.

There was some talk about using a hose with a bend, so that any oil thrown up by the rocker assembly would hit the hose and run back down ... just try it and see what happens.

i think if your motor is screaming at 13,000rpm you probally will see a conrod anway

If you decide to race it, it is not a question if you should or should not...you have to.