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Talking Variable Valve Timing With Billy Godbold, COMP Cams

Billy Godbold has been at COMP Cams for more than 15 years and has been in charge of COMP’s camshaft design and profile development for more than 13 of those years.

Godbold's responsibilities include developing camshaft profiles for leading racing series, including NASCAR series, CART, IRL, NHRA, 24-hour endurance series, sport compacts, motorcycle, ATV, go-cart and almost every other conceivable type of 4-stroke engine application.

Godbold was raised around machinery and engines on a rural farm in Mississippi. Growing up, his two passions were science and going faster. While receiving his B.S. in Physics at Rhodes College in Memphis, TN, he decided to make one of these passions his career and the other his hobby.

Godbold was awarded a Ph.D. tract graduate fellowship at Florida State University. After receiving his M.S. in Physics from FSU while working with the Nuclear Physics Group, he moved back to Memphis and started working for Competition Cams, Inc. as a technician. He soon decided that going faster was the career he wanted and science was a tool and a hobby.

Engine Builder magazine recently discussed the latest trends and developments in variable valve timing technology with COMP Cams’ Billy Godbold.

• Explain how variable valve timing technology has changed over the years:

Variable valve timing started as expensive add-ons on non-domestic (small) engines to improve performance. The movement toward this technology is something we have been elbow deep in since the Honda VTEC engines became popular in the mid-1990s.

The “new” part is that now simple variable valve timing systems are prevalent on most domestic V8 engines and can be very beneficial for performance. Clearly the prominence of “cam phaser” engines that allow the computer to advance or retard the camshaft or camshafts has brought variable valve timing front-and-center in the automotive aftermarket.

• Where are we currently, with technology that's applicable to engine builders?

Much like with electronic ignition and electronic fuel injection in the past, the good OEM systems becoming readily available has dramatically improved the accessibility of variable valve timing to engine builders. Converting a non-VVT engine to VVT would be very expensive for a one-off application. However, taking advantage of these systems where they already exist is something we should not fear.

• Are there particular “problem” engines? Conversely, are there some that are just right?

The popular domestic engines, such as the GM L92 and L99, Ford 3V and 5.0L Coyote and Hemi 5.7L and 6.4L all have very user friendly camshaft advance and retard (“Phaser”) systems.  These should be the easiest to use for most engine builders.  It is quite common for performance engine builders to either advance or retard camshafts to optimize the power curve of a given engine.  These phaser systems allow the engine builder to tune the camshaft advance/retard setting as a function of RPM and other inputs.

• Can engines without VVT be retrofitted? What's involved?

It is difficult to apply these systems to engines without the required oil passages for the systems. It is possible to retrofit, but you would want a block with all of the requisite passages. Hence, going back to a 1980s engine would be quite difficult.

• Some “old school” performance guys have been reluctant to embrace the technology. What do they want in its place, why do they make the change and what are the potential (or actual) drawbacks?

For most of these engines, we offer either timing sets or phaser “locks” to fix the cam position. Fixing the cam position may work great in narrow RPM band race applications, but gives up quite a bit over a 5,000+ RPM operating range. The hardest part of any variable cam position system (when it comes to aftermarket cams) is being certain of proper piston to valve clearance at the motion extremes. One reason to lock the camshafts in race applications is to run the biggest cam possible without clearance issues.

• What don’t people understand about this technology?

I believe the most common misunderstanding has to do with the response time and accuracy of these systems.  We have been amazed at how accurately these systems can position the camshafts, even when higher engine speeds or higher valve train loads are applied.

• Is this an OE thing only? What does the aftermarket offer in terms of VVT?

At this point, I believe the aftermarket first needs to become comfortable optimizing parts for the OEM systems.  After some time gaining acceptance, then we can begin working on “from scratch” aftermarket systems. That was likely the same course followed on electronic ignition and fuel injection systems that the aftermarket later had access to and developed.