What should I consider when switching to a high compression head?

[Hurvinek]

Hi y'all

Thank you very much for your respond.
I will try the hc head in the Van, it may give a little pit more power, at least I hope so.
All the others are running systems and will therfore be untouched.

Oliver

[AustinWood]

We fitted a High compression head to the original engine in our 1929 car. It added about 5mph to the cruising speed but the engine note was harsher. We did not change anything on the carburettor or ignition, but we have manual advance/retard controls. We do have a Phoenix crank so that was safe.
After a while we went back to the low compression.
I have now fitted another engine, based around mainly 1933 components. This has the HC head and runs very well. Very slightly harsher maybe but definitely better performance. Altogether good.
It's worth a try because it is easy to switch back if you don't like it.
It is a good idea to check that the valves aren't hitting the head. Put the head in place with no gasket, no spark plugs and not bolted down. Hold the head down with one hand and spin the engine withe the other. If the valves are coming too close you'll feel the head moving on the engine.