Olds 307 and 403
Well-known member
What cfm is the Holley carb? It will probably be way rich as is and the square to spread bore adapter as mentioned. He will need stock replacement pushrods for a 85 to 90 Olds 307 Vin Y. They are different as that motor has the taller roller lifters. Surprised a flat tappet doesn't go flat using the roller lifters.