GlenL

What work on the heads would you recommend for stock valves?

I'm thinking to port match and clean up the insides leaving a 60-grit surface.

Is that a 48mm? How does a 52mm valve even fit?!

I think someone mentioned needing to go the a 11/32" stem with new guides and new springs. Correct?

slate blue

I'll chime in for my two cents, first the 52 mm valve, it was 11/32" not 11/16'' it is fitted and flow tested in the AussieV8 thread to a 104 mm bore engine and you can view the numbers obtained in that thread.

The 48 mm valve is fitted to a 100 mm bore and is a pretty good size for a 100 mm bore. I think it did 244 cfm @0.500". Now this is important, it did go over 250 cfm with an aftermarket valve that was flatter in design and slighter bigger at 48.5 mm. However we stuck with the Porsche valves as that is what we had and I intend to sell this engine after it is dynoed.

So saying that, I think an aftermarket valve around 47 mm in diameter and using an 11/32" stem could be the trick weapon as the extra diameter allows the porter to clean up the bowl and seat area. They will also be lighter too.

I won't go into stock valves but you can look again at the AussieV8 thread as the head tested in the beginning was ported by my first cylinder head porter. Peter wasn't happy with it but it still offered and improvement over stock.