Did you enlarge the exhaust ports or just polish them ?

If so how did you base your port size ?

Thanks

 

At the risk of being impertinent (since I have World heads), I'll venture an input. This is based on the Standard Abrasives DIY guidelines.

You really don't want to increase the size of the exhaust port much at all if any. You want a slight step up from the port to the exhaust manifold/header port for anti-reversion properties. Clean up the throat & guide, polish everything up, that's about all you need/want to do to the exhaust ports.

If your exhaust port is bigger than your manifold/header port, then make them bigger to match if possible.

FWIW, I found porting the exhausts to be particularly satisfying, especially for a first-timer. The "look" of the job made for a dramatic before/after comparison.