We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re talking valve spring pressure and how it affects valvetrain performance.
C.K.• Somerville, OH
Q: I have a 1967 Ford Bronco. Being the serious gearhead that I am, I want as much power as I can get out of the 302 that’s in it. So far, I’ve added an Edelbrock Performer carb and intake, headers, roller rockers, and a Summit Racing .471-inch lift cam kit. I have a set of Crane “universal fit” dual valve springs–should I install them, too? I’m on a tight budget; is there anything else you could recommend that won’t break the bank?
A: Using universal valve springs is like wearing a pair of universal shoes–not ideal! If you use valve springs with too much pressure, you will wear the lobes off the camshaft. If the springs are not strong enough, your valves will float at higher rpms. The camshaft you’ve installed requires valve springs with an installed height of 1.703 inches, a seat pressure of 95 pounds, and an open pressure of 260 pounds at 1.200-inch height. Try a set of Crane Cams 99833-16 springs.
It sounds like you’ve addressed the incoming air and fuel and have the outgoing exhaust handled. As far as additional upgrades, the next step would be to ensure that the air/fuel charge is properly combusted in the cylinders. For this, we recommend adding an ignition system, such as an MSD 6A ignition, to your truck. Also, your engine would probably benefit from having the distributor advance curve adjusted.