Im contemplating taking a 572 that made big power and dropping compression just enough to run pump fuel on the street and maybe using a timing retarder and separate tank with good fuel.
But my question is is I drop the compression just for pump gas only how much power loss would you think I would see?

Edit to add info
572 with small dish piston
Victor heads ported and the combustion chamber has been opened up to the big bore size unshrouding the intake valve a lot!
275/283
715/675
Indy intake dominator
Made 930/840 at 6400rpm

Looking at the pistons and the chamber it doesn't look like a lot of compression because a lot of material was removed in the chamber.
Haven't CCed the heads yet but I'm thinking it can't be much over pump gas compression now.

What is the ratio now?

I don't know but looking at that big combustion chamber and a dish in the piston i can't imagine more than 12:1. Like I said haven't checked the chamber yet so that's just a guess comparing stock chamber to this one.

And what fuel made 930Hp?

C12