Drag racers have been searching for tricks to gain horsepower since day one, and there are lots of ways to do it without spending a tremendous amount of time or money. One of the biggest downfalls of the original small-block Chevrolet design was the valvetrain, due to a lack of efficiency—lots of flat surfaces meeting other flat surfaces, leading to unnecessary friction. And even though stamped steel rocker arms were perfectly fine for daily use in your grandmother’s Caprice, they just don’t cut it considering the affordability compared to new roller rocker arms.
Whether you’re dealing with a mostly stock junkyard small-block or a highly modified race engine, rocker arms play a big role in freeing up horsepower and helping reduce friction in the valvetrain. There are numerous options for small-block Chevy roller rocker arms. First is a stamped steel rocker arm with a roller tip, which is the least expensive option. Second is an aluminum or chrome-moly steel rocker arm with the stock 1.5:1 ratio. Finally, you can opt for the same type of aluminum or chrome-moly rocker arm with a higher ratio to effectively increase the maximum valve lift. We have seen many combinations, including staggered rocker arm ratios (exhaust rockers with a higher ratio than the intake rockers or vice versa).
You can easily gain 20 horsepower with a rocker arm swap, but installing them isn’t quite as simple as removing the stock rockers and bolting on new ones. For seasoned car guys, it’s a quick process, but if you’re new to the task of setting valve lash you might want to take some notes before you tackle the project. If you’re dealing with an engine with quite a few miles on it, now would be a good time to replace the flimsy stock pushrods with a set of hardened pushrods. For our 327ci small-block Chevy, we went with a set of Comp Cams High Energy 7809 pushrods, which are 7.266-inches in length and 5/16-inch in diameter. Please note that the 7.266-inch length is designed for use with Comp Cams’ hydraulic roller retrofit camshaft. A standard small-block Chevy with a flat tappet camshaft would use a 7.800-inch pushrod, but many factors, including deck height, head gasket thickness, rocker arm ratio, and more go into determining proper pushrod length.
The rocker arms we chose for our combination are Comp Cams 1601 Ultra Pro Magnum units, featuring a 1.52:1 ratio and 3/8-inch stud fitment. These rocker arms are ideal for a high-performance build that will see plenty of street use, and that’s exactly the intention with our mild 327ci small-block. It does have a Comp Cams hydraulic roller camshaft in place, but the installation process of the new pushrods and rocker arms apply to small-block engines with flat tappet or roller tappet designs. Take a look at the quick and simple process, and check out the sidebar on adjusting valve lash if you’re using hydraulic lifters.
1. For our 327ci small-block Chevy, we’re swapping to a set of Comp Cams 1601 Ultra Pro Magnum roller rocker arms. They feature a 1.52:1 ratio and have a super sturdy design for the ultimate in valvetrain stability. The pushrods are Comp 7809 High Energy pushrods, which measure 7.266 inches—a perfect fit for our hydraulic roller retrofit kit.
2. In most cases, you can swap rocker arms and pushrods with the intake manifold in place, but we had our top end apart for another upgrade, so leaving the intake out of the way made it easier to see what we’re doing. In case you were wondering, the cylinder heads are Dart Pro1 Platinum, with Comp guideplates and 3/8-inch screw-in rocker arm studs.
3. Before we start sliding pushrods into place we need to check our valvetrain geometry, as rocker arm ratio can affect the necessary pushrod length. It’s best to do this with a pushrod checker tool, which is adjustable. Checking the geometry is quick and easy—we start by coloring the valve stem with a marker.
4. Then, it’s time to slide at least one pushrod, or your pushrod checker, into place and install the rocker arm. This works best if the engine is on top dead center on the No. 1 piston, as that means the intake and exhaust lifters are on the base circle of the cam. We adjust the valve lash and spin the engine two full rotations.
5. After removing the rocker arm, we can take a look at the pattern left by the roller tip. The idea is for the roller to be centered on the valve stem, so our pushrod length is spot on for our combination. Be sure that the valve that you’re testing has a lifter that is pumped up, as a spongy lifter may affect the results of your geometry test.
6. We used Comp Cams Valve Train Assembly Spray on the valve stems and also sprayed the pushrod ends and friction areas on the rocker arms. Just like any new engine part, lubrication is important on initial startup.
7. Setting valve lash while the engine is cold is not ideal but it will get you in the ballpark and allow you to come back and fine-tune the valve lash after the engine has come up to temperature. Most hydraulic lifters are pre-loaded one-half turn past zero lash, which is the point where the rocker arm begins to apply pressure to the pushrod.
8. Using locking rocker arm nuts, we spun our 5/8-inch wrench one half turn to achieve the proper valve lash. Then we tightened the locking Allen head fastener. The sequence in which valve lash is adjusted can be confusing, but the idea is to adjust the valve lash when the lifter is on the base circle of the camshaft.
9. A remote starter button really comes in handy when it’s time to adjust valve lash, as you can bump the engine around without having to reach inside the car or turn the engine over by hand. One side is installed and adjusted, so now we can tackle the other side of the engine.
10. We hated to cover up our brand-new roller rocker arms, but if you’re going to cover up the good stuff, you might as well get some cool valve covers. Comp Cams makes these tall aluminum valve covers with a black, textured finish. They were a perfect fit for our hopped up small-block, which now has a stable and efficient valvetrain.
Adjusting Valve Lash
Valve lash adjustment is something that nearly all types of Chevrolet engines require when rebuilding or refreshing the valvetrain. It’s not as simple as tightening a bolt until it reaches a certain torque value—it requires a bit more finesse and a lot more time. Whether you’re running a solid lift or hydraulic camshaft and lifters, proper valve lash is very important to the wellbeing of your engine. Valve lash on solid lifter applications is adjusted by tightening the rocker arm nut until reaching a certain tolerance (using a feeler gauge) between the rocker arm tip and valve stem. Hydraulic lifter engines are often adjusted one-half turn past zero lash to preload the lifters. Zero lash is the point at which the rocker arm begins putting pressure on the pushrod while the lifter is on the base circle of the camshaft. There are some other opinions on how far past zero lash you should go, but in general, most camshaft companies advise one-half turn.
Valve lash adjustment offers the best results when performed at operating temperature. Old-school guys tell stories about adjusting valve lash while the engine is running, but that makes a mess and it’s a little tough with a locking rocker arm nut. Adjusting valve lash on a cold engine has drawbacks as the lifters may be a little soft, but you have to start somewhere. We like to do a baseline adjustment and then go back and fine-tune it after the engine has been brought up to operating temperature.
Valve lash can only be adjusted when the lifter is on the base circle of the camshaft. To achieve this, watch the valves open and close as you rotate the engine. When the exhaust valve is just beginning to open, you can adjust the intake valve on that cylinder. Then, rotate the engine more and adjust the exhaust valve on that cylinder once the intake valve you just adjusted is nearly closed. Do this routine for all eight cylinders and you’re ready to button it up and fire the engine.
There’s a short cut to adjusting valve lash on a cold engine, as long as you’re planning to go back and dial it in at operating temperature. First, rotate the engine to top dead center, being sure that it is on the compression stroke for the number one cylinder. You can easily check this by popping the distributor cap off and ensuring that the rotor is pointing to the front of the car instead of the rear. With the No. 1 cylinder at top dead center, you can adjust the exhaust valves for cylinders 1, 3, 4 and 8. You may also adjust the intake valves for cylinders 1, 2, 5, and 7. Spin the engine one full rotation, so that the No. 6 cylinder is at top dead center on the compression stroke. Then, you may adjust the exhaust valves for cylinders 2, 5, 6 and 7. Finally, adjust the intake valves for cylinders 3, 4, 6 and 8 and you’re done.