For roller tipped rockers without guide plates there is some mention of a need for clearance in the pushrod hole on SBC heads when using 1.6 ratio rockers. I bought both 1.5 and 1.6 ratio sets. I am hoping for less heat with the roller tips because there is tremendous scuffing friction with the stock rockers. At present I am going to use the 1.5 ratio rockers mainly to run a cooler engine, but how can I check for pushrod binding with the 1.6 ratio rockers? If there is side rubbing of the pushrods with the 1.6 rockers, what is acceptable or should there just be no contact with the edge of the hole to be sure I won't bend a pushrod? I should have clearanced the holes when the heads were rebuilt. I have a very low lift cam with only 0.390 intake and 0.410 exhaust and hoped to add lift with the 1.6 rockers but since I have read that the stock rockers are often close to 1.4 ratio, using the 1.5 ratio rockers should give a slight increase in lift with less danger of bending a pushrod. I am sorry to keep asking questions about my engine which I have not started yet but I am working on the car every day and will eventually get to the engine where I plan to start out using the 1.5 roller tipped rockers from Speedway. (Today I installed the rear bumper, adjusted the stalk Model-A taillights and started installation of the LED turn signals.)

Don Shillady
retired Scientist/teen rodder