Jim Smart
March 1, 2007
Photos By: Benton Jackson

Camshaft Tech Talk

When Blair brought Marvin his 427W in a basket, he also brought an aggressive hydraulic-roller race cam from Schneider Racing Cams. This is an off-the-shelf bumpstick ready for racing. Blair wants to use his '66 Mustang fastback on the street as well as the track, though. Here are his cam specs:



Schneider Racing Cams Grind No. 284-RH
Running Specifications
Running Duration:284/284 degrees
Lobe Centers:112 degrees
Lobe Lift:.340/.340 inch
Valve Lift:.544/.544 inch
Peak Torque:3,500-5,000 rpm
Specifications At .050-inch tappet height
Intake Open:2 degrees BTDC
Intake Closed:42 degrees ABDC
Intake Centerline:110 degrees ATDC
Exhaust Open:46 degrees BBDC
Exhaust Closed:-2 degrees BTDC
Exhaust Centerline:114 degrees BTDC
Duration at.050 inch:224/224 degrees
Cam installed 2 1/2 degrees retarded (to enhance horsepower)

Duration and lift will prove the most challenging for Blair. When you're shopping for a cam, duration, lift, and lobe centers are the main concern. A lobe center of 112 degrees isn't the issue here-duration and lift are. Because duration is 284/284, which is rather lengthy, this will affect both idle quality and manifold vacuum. The same can be said for valve lift, which also robs vacuum and idle quality. Duration has a direct bearing on valve overlap (the period when both valves are off their seats). Overlap helps power on the high end, but hurts idle and manifold vacuum down low. These elements are what will make Blair's Mustang restomod a chore to drive on the street, yet incredible when it's time to go road racing. Our message here is simple: You cannot have both superior street and race qualities in the same engine.

What Is a Dry-Sump Oiling System?

This is what a typical dry-sump oiling system looks like. Shown here is a three-stage pump (actually three pumps-one for pressure and two for scavenging). You can have as many stages as you want, depending on how much scavenging you need. Generally, there is one stage for pressure and at least one stage for scavenging. In this application, we have one pressure stage (capped) and two scavenging stages. The scavenge ratio is 4:1, which means it has the capacity to return way more oil than it receives. This means more power because an efficient scavenging system will reduce crankcase pressure.

A dry-sump oiling system does away with your engine's conventional oil pan and internal pump, replacing them with a beltdriven external pump system and low-profile oil pan. Dry-sump oiling systems are designed specifically for racing even though they may be used in street applications. They are used in racing to ensure a constant supply of oil under high lateral g-forces and hard acceleration, which is crucial to engine survival at high rpm.

Because racing engines demand a continuous supply of oil under pressure at high rpm, a dry-sump system is designed to keep them well supplied. Conventional wet-sump oiling systems can develop oil supply problems at high revs, cavitating the oil pump and causing an oiling system to areate (suck air), causing major engine damage in nanoseconds. At high rpm, an engine's internal oil pump can empty a deep-sump racing oil pan, rendering moving parts dry in short order. At high rpm, all of the pan's oil winds up at the top of the engine, filling valve covers and the lifter valley completely-robbing important moving parts of pressurized lubrication. The dry-sump oiling system gives us more control of where the oil is. A dry sump gets oil back to the reservoir (oil tank) as quickly as it leaves.

A dry-sump oiling system consists of an external multistage, a beltdriven pump, cog-belt drive pulleys, high-pressure hoses and fittings, and a special dry-sump oil pan. The pan is designed to channel oil back to the pump and reservoir. When we speak of pump stages, we're talking individual pumps (stages) designed to move oil. Typically, there is one pump to provide oil under pressure to give us an oil wedge between moving parts. Then, we have at least one scavenge pump stage to collect oil and return it quickly to a reservoir. We can scavenge oil where a deep sump pan would normally be. We may also scavenge oil at the lifter valley and even high up at the valve covers. Much depends on the kind of driving we're going to be doing.

Reunited and It Feels So Good

Here is Blair Jennings at an SCCA Trans Am race at Riverside, California in 1970. That's the Grabber Blue Boss 302 campaigned by Jefferson Enterprises, powered by an MCE-built Boss 302.

Blair met Marvin long ago when he was in adolescence. At the time, Marvin was building race-winning Boss 302 engines for SCCA Trans-Am competi-tion. The Grabber Blue '70 Boss 302 Mustang campaigned by Jefferson Enterprises went after big game with a Boss 302 engine built by Marvin's Competition Engines (MCE). Blair's father looked to Marvin for his expertise-and he got it, using powerful small-blocks from MCE Engines.

As the fever of intense Trans-Am competition faded and faces changed, Marvin moved on, and so did Blair and his father. It would be more than 30 years before Marvin and Blair saw one another again. More than a year ago, Blair brought his engine to Marvin for a second generation of Jennings engines built by Marvin's Competition Engines.