Tell me why?
I just picked up an 86 grand prix. It's supposed to be all stock. When I pulled the valve covers off the casting numbers of the heads are 462624 which was 350 only heads. I got the intake number which is a 305/350 intake. I can't imagine someone putting the 624 heads on due to the combustion cc difference. I can't get to the block casting number either. Very weird. Maybe i'll be lucky and someone put in a 350.