You’ve got questions. We’ve got answers. We work with the Summit Racing tech department to tackle your automotive-related conundrums. This week, we’re talking about aluminum vs. steel roller rockers and rocker ratio in daily-driven, high-mileage fleet vehicles.
Q: I have some questions concerning the use of aluminum roller rockers on a street engine with a stock-type camshaft and valvetrain. We have shop trucks with Chevy small block V8s that routinely see 250,000 miles and do a lot of towing for several thousand miles at a stretch. The engines are 350 cubic-inch crate engine with we modify with headers, an aluminum intake manifold with a four-barrel carburetor, and an MSD HEI distributor with 8mm wires.
I know that the stock stamped steel rocker arms cause friction, which puts additional wear on both the rockers and the valve stems. I also know the roller rockers will reduce this wear considerably, plus we can gain some extra power by upping the rocker ratio from the stock 1.5 to 1.6.
What I don’t know is how long aluminum roller rockers would last in our engines. Are they up to the task? If I go with a 1.6-ratio rocker, would it give us some extra power without weakening the stock valve springs? Would we need screw-in studs, stronger pushrods, and guide plates? If the aluminum rockers will provide some extra power and less valvetrain wear without durability problem, I will definitely use them.
A: We don’t think aluminum roller rocker arms will deliver everything you want.
Used on a daily driven engine with a stock valvetrain, the rockers will last approximately 20,000-30,000 miles with regular oil changes. Since you run your engines for 250,000-plus miles, you would end up replacing aluminum rockers quite often.
As for power, a 1.6-ratio rocker will increase valve lift and power, but won’t affect duration (the time the valves are open) or the engine’s powerband. If you decide to run a 1.6-ratio rocker (aluminum or steel), you should check for coil spring bind.
The minimum clearance between the coils at maximum valve lift should be at least .060 inch.