I have got 43 th head gaskets on my 489 if I drop them to 23 how much compression would I gain my car is 9.7.1 I'm looking for more power I got the big 335 afr heads with flat tops in her, I got it in a 68 chevelle. My buddy got a 69 camera with less power but he can out run me by 2 or 3 links mind dynoed at 649 Hp 591 tq. He said his camero is just as heavy idk