Hot Rockers

Crane's Slick 1.6 Stamped Rockers

Jeff Smith Jul 1, 2002 0 Comment(s)
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Have you ever noticed that some engines just seem to run better and make more power than others? Often, it can be attributed to what might be considered an insignificant detail. Take the lowly stamped-steel rocker arm. In the grand scheme of things, stamped rockers get no respect and certainly never bask in the limelight. But we recently learned something intriguing about Crane's tried-and-true stamped-steel, long-slot, 1.6:1 rocker arms that surprised us. Everybody knows that more rocker ratio will increase valve lift. Theory says if you replace a stock 1.5:1 rocker arm with a 1.6:1 rocker, valve lift will increase throughout the lift curve. Let's take a small-block cam with a max valve lift of 0.450 inch with a 1.5:1 rocker arm. Install a 1.6:1 rocker and the max valve lift jumps to 0.480 inch. That's a healthy 0.030-inch increase in valve lift. But there are overlapping schemes working here that deserve to be investigated.

First of all, rocker arms rarely maintain the same ratio throughout the entire valve-lift curve because the rocker arm moves in an arc as it generates lift. Roller rockers do a good job of maintaining their stated rocker ratio throughout the entire lift curve, but the same is not always true of stock-stamped factory or budget stock replacement rocker arms. These pieces often test far short of their rated rocker ratio. To prove this point, we tested several supposedly 1.5:1 small-block rocker arms and discovered rocker ratios between 1.30:1 and 1.49:1. We also found that the ratios changed throughout the lift curve, increasing the ratio as lift increased. This reduced ratio means lost valve lift and potentially lost torque and horsepower. The difference is not 50 hp, but it is significant.

The opposite of the weak stock rockers are the Crane Nitro Carb stamped-steel, long-slot, 1.6:1 rocker arms. At first we were skeptical that a stamped rocker could maintain that ratio. However, when we tested several Crane rockers, we discovered that they exceeded the 1.60 ratio in almost every case. Study the accompanying chart and you can see that the Crane rockers actually deliver far more than their advertised ratio throughout the entire lift curve.

We tested several stock rockers that had come off of a late-'60s small-block and were shocked at the low rocker ratios we measured. After checking six rockers, only one reached 1.55:1 while the rest never exceeded 1.49:1. Each rocker tested lowest at low valve lifts and then increased the ratio as the rocker approached maximum lobe lift of 0.300 inch. In all fairness, we also tested several late-model factory-guided rockers and these pieces tested better, with ratios from 1.45:1 to 1.52:1.

We found something interesting when we compared these weak lift curves to the Crane stamped steel 1.6:1 rocker. As you can see from the chart, the Crane is a true 1.6 rocker that offers a curve from 1.62 up to 1.66:1. Compare the valve lift at 0.300-inch lobe lift and the >> Crane delivers 0.020 inch more valve lift at 0.100-inch cam lift, 0.030 inch more at 0.200-inch cam lift, and 0.032 inch more valve lift at 0.300-inch cam lift. As a point of reference, we used the best stock rocker to compare to the Crane in this example. However, using one of the worst stock rockers, the Crane 1.6 delivered 0.030-inch more valve lift at 0.100-inch cam lift (0.162- versus 0.132-inch valve lift).

Will bolting on a set of Crane's 1.6:1 long-slot stamped rockers transform your sled into a rocket? Probably not. Even though the increased valve lift could be as much as 0.045 inch, which is definitely significant, that's not the same thing as bolting in a bigger cam because the cam with the larger lift also offers increased duration, which makes a big difference in peak horsepower. But increasing valve lift will generate the kind of midrange torque that you can feel in the seat of your pants.

To further sweeten the deal, these Crane 1.6:1 steel rockers are pleasantly affordable. Researching prices in the Summit catalog, we found a set of Crane 1.6:1 long-slot stamped rockers for a reasonable $115 versus $172 for a set of Crane Energizer aluminum roller rockers. Where else are you gonna get more lift for less money?

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This little rocker arm may not look like much, but it certainly does its job. The Crane 1.6:1 long-slot stamped rocker is not only affordable, but it also measures an impressive 1.66:1 ratio at max valve lift.

All rocker arms travel through an arc as they move from zero to maximum lift. Minimizing the lateral movement of the rocker tip in relationship to the valve will improve the rocker ratio. Proper pushrod length also minimizes rocker geometry problems.

Testing the Crane 1.6:1 long-slot rockers gave us the rocker ratios that are in the accompanying chart. Here, we are using a pair of dial indicators to measure both pushrod (cam lift) and valve lift. Given these two values, we calculated the rocker ratio at each lift.

At first we tried measuring cam lift from the pushrod cup, but the indicator kept slipping outward, which multiplied the lift numbers.

Tim Moore then welded a small shelf on the pushrod, which stabilized the cam-lift measurements.

Durability with stamped rockers is often questionable. One simple improvement to any stamped rocker is to grind the stamping flash from the top of the pushrod oiling hole. Use a die grinder or an abrasive wheel to remove this sharp edge that could cause a stress crack that would eventually lead to a broken rocker arm in the pushrod cup area.

When installing new rocker arms, always coat the pivot ball and the bottom of the rocker area with moly lube. This will protect the rocker with sufficient lube until the engine oil takes over. We always add engine oil to the rocker ball area as well right before the engine fires.

The Crane stamped 1.6 rocker (right) offers a noticeably longer slot to prevent binding on the rocker stud compared to the stock. The rocker on the left is a late-model guided style that should not be used with guide plates since this will cause binding.

Crane Gold Race aluminum rockers are the best roller rockers Crane makes and are available for small-blocks with ratios from 1.5 to 1.7 and are strong and durable.

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