Karl Benz is typically credited with designing and building the first automobile powered by an internal combustion (IC) engine, but it was almost 80 years earlier, in 1807, that a Swiss by the name of Rivas truly designed and built the first automobile powered by an IC engine. And it ran on hydrogen, no less! Now there are production cars that are capable of telemetry downloads while travelling 200-plus mph. As far as technology has evolved in the last two centuries, there are some basics about engines that just haven’t changed. With four-stroke engines, we have to ingest fuel and air, we have to contain it, we have to ignite the fuel/air mixture, and we have to expel the spent exhaust. Of those four processes, valves and the valve job are involved in three. It comes as no surprise then that the valve job is one of the most critical elements of a well-performing engine.
When the time comes to freshen up the valve job on your engine, or if you are building a new combination, not a lot of time is typically given to the specifics of a valve job. It is most often just billed as “stock” or “competition.” What does that mean? What are the considerations for what type of valve job to get? And what performance benefits can you expect from different valve jobs? Those are some of the questions we have at PHR, and in speaking with different engine builders from around the country, we have received a surprisingly different mix of responses.
The mule for this test was...
The mule for this test was a mostly stock Vortec 350 that had been sitting in an algae-covered four-door Nova for the last seven years. After pulling the pan and heads to check for critters, it was declared sound and ready for service. An MSD 6AL2 and matching Pro Billet distributor were borrowed from a 327, and the headers were typical 1⅝-inch swap meet specials. The custom COMP Cams hydraulic roller (with 226/239 duration at .050 and .521-/.554-inch lift on a 113-degree lobe separation, installed at 109-degree intake centerline) was from an old nitrous 383 small-block, but hey, it fit.
Brothers Rick and Randy Ferbert, who recently competed in the 2011 AMSOIL Engine Masters Challenge with a Bow Tie Vortec-headed 383 small-block Chevy, mentioned during teardown (look for an upcoming feature article on the all-iron small-block) that they put a 50-degree valve job on their engine. That’s traditionally been reserved for high-lift, high-rpm race engines. What gives? A conversation with Pro Stock engine builder Jon Kaase seemed to indicate it might not be worth it. “We tried different valve jobs a few years ago, and really didn’t find much there so we just stick to the same one we always use [on the high lift engines].” Kaase mentioned he ran a 30-degree valve job on the potent Pontiac he entered in the Engine Masters Challenge a few years back, but was unsure whether that was a good or bad thing. “If the seat ID is the same when you got all done below the angles, I don’t know if it’s going to make a real big difference.” For the most part, Kaase recommended a common 45-degree valve job for “normal” lift engines. The fact that the Ferberts had such a steep angle on their small-block with only a .650-inch lift cam got us scratching our collective noggins and wondering how deep we could delve into the geometric world of valve jobs without an advanced engineering degree.
Determined to unearth some valve job secrets, the PHR team located a mild ’96 Chevy Vortec 350 and tested the limits of the flow bench and engine dyno. Food containers were strewn about, and spouses left grumbling while monomania dominated the three-day thrash. The test engine was a basic 9:1 re-ringed truck engine sporting a COMP Cams hydraulic roller cam we had floating around, Vortec heads with a super-basic bowl blend, and a dual-plane intake with a Holley double-pumper. Nothing special, but representative of a common street brawler. The plan was to flow the heads with the factory 45-degree valve job and run it on the dyno at Revolutionary Performance and Machine in White House, Tennessee. After a string of consistent baseline pulls, the heads would get yanked, a 35-degree intake valve job done, flowed, and dyno’d again. Finally, off with the heads for a 50-degree intake valve job, flow test, and another string of dyno pulls. The results were worth the effort!