Spring Fling

Weighing the individual components quickly identifies the advantage that the conical spring has over the standard single spring. As our sidebar illustrates, the top half of the conical spring is 57 percent lighter than its PN 911 counterpart.

Roller camshafts tend to tax valvesprings because of fast acceleration rates. This, combined with load spikes from valvetrain deflection can really put the hurt on a valvespring if it is not carefully matched to the rest of the valvetrain.

Testing a valvespring in a load tester like this digital machine will accurately test the spring's load capacity, but it tells us nothing of the spring's characteristics in dynamic situations. As our dyno test indicates, the beehive springs' reduced mass may be worth more than it appears in terms of valve control.

Most enthusiasts purchase aftermarket cylinder heads already assembled mainly for convenience. Unfortunately, the valvesprings on these heads may be somewhat generic and not up to controlling the valvetrain in your performance engine, especially when it comes to the latest generation of roller cams on the market. You may want to consider purchasing the heads bare, investing in higher-quality components and assembling the heads yourself.

One of the biggest valve float culprits is a heavy intake valve. It's not unusual for a big-block to run a 2.19- to 2.30-inch intake valve. It's possible to save a little weight with an 1 1/32-inch (0.343) stem instead of a 3/8-inch (0.375) diameter, but a stainless steel Rat valve is still between 130 and 160 grams, while a 2.08-inch stainless small-block valve weighs much less at around 115 grams.

We used a GM Performance Parts 454 H.O. Rat motor as our test mule mainly because big-blocks are notorious for suffering from valve float due to their large, heavy valves, high 1.7:1 rocker ratios, and long pushrods. Just by changing to the conical spring, the engine picked up both low-speed torque and top-end power.