How To Trick Out Your Stock Cylinder Heads

Most aftermarket performance valves are made from stainless steel, but Massingill says calling them stainless is the same as calling the stuff on the ground dirt. There is a wide variety of stainless steel alloys used to make valves. The best alloys, like Inconel, are stronger and can take more heat without deforming. They are priced accordingly. Most manufacturers have different levels of valves, ranging from budget to race, and the prices can be as low as $25.00 or more than $200.00 for a set of eight. Massingill recommends buying the best valves you can afford.

Milling
If you've got heads with relatively large combustion chambers, you can have them machined in an attempt to raise the compression ratio. Discuss this option thoroughly with your builder, though. You don't want to take off so much material that you'll have to machine the intake manifold mounting flange or need to buy nonstandard pushrods to get everything to fit. Massingill tells us milling the heads by as little as 0.030 inch can result in a performance gain.

Studs And Rocker Arms
Stock small-block Chevys have 7/16-inch pressed-in studs, and these are often replaced with 3/8-inch screw-in studs. Of course, you'll have to install new rocker arms to match the bigger studs to prevent them from being pulled out by the rocker arm. This is not a bad thing, however, because stock, stamped-steel rocker arms flex, and tests have shown they often do not deliver the ratio they are supposed to. If a stock rocker arm ratio is 1.5:1, it will open the valve 1.5 times the amount of lift provided by the cam lobe. In reality, some stock rocker arms have been shown to only deliver a ratio of around 1.44:1.

Comp Cams and Summit Racing sell a set of stamped rockers with roller tips for less than $160.00. They are much stronger than stock, and according to our sources are as strong as the flashy aluminum pieces and lack only the roller bearing fulcrums. Some builders vary the ratios from intake to exhaust, too. Adding a bigger-ratio rocker to the exhaust valves can often help out heads with weak exhaust ports by opening the valves a little faster.

Springs
Spring choice is a trial-and-error process and is affected by a number of factors, including the weight of the valves, retainers, and keepers; the type of lifters you're using; and the shape of the cam lobe and how quickly it opens and closes the valves. Massingill says it's better to run spring pressure that's a little too high than pressures that are too low. Though too much spring pressure can flatten a cam lobe, too little pressure robs all your high-rpm power. The valves will float because the springs aren't strong enough to make them close fully at high engine speeds. An experienced engine builder will be able to recommend springs that are good for your combination. However, if you have access to a dyno and feel like experimenting, Massingill says to keep adding spring pressure until valve float goes away.

By John McGann

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