According to Westech's Steve Brule, the camshaft chosen for the dyno test featured a large amount of duration-too much for the application due to the engine's limited compression. With a pump gas-compatible engine such as this, the increased duration actually allows cylinder pressure to be reduced, slightly lowering peak power.
"This type of engine (540-cid Mark V) can handle a lot of lift, but too much duration is a detriment," says Brule. "The excessive duration, however slight, actually bleeds off intake charge. It negatively affects the volumetric efficiency and increases the exhaust gas temperatures. But the higher lift is not a problem; in fact, it gets the valve moving slightly quicker, helping fill the cylinder more fully, making more power. As long as you don't have valve to piston problems, lift is only a positive thing."
The camshaft selection process has long been a black art by both pro and novice engine builders, leaving lots of room for interpretation. How do you know you have purchased exactly the right camshaft for your engine? In the past there has been only one way-to trust in the expertise of those who are believed to be experts. Today, real experts are easy to find, such as those answering the phone at the COMP Cams Cam Help hotline. Unfortunately, many builders don't make the call and rely on their friends and pseudo experts to advise them. With engine building requiring not only cubic inches, but also cubic dollars to build big power, it's safe to believe there are now two very reliable sources for camshaft advice-Cam Help and CamQuest 6
Mark V Quick Spotter Guide:
* One-piece oil pan gasket
* 10-bolt timing cover with gasket (the Mark VI uses a six-bolt cover with an O-ring)
* Includes oil cooler option in the galleys for a remote oil cooler
The Keith Black hypereutectic...
The Keith Black hypereutectic pressure cast-aluminum pistons were dressed with Akerly & Childs piston rings and set at 10.25:1 compression.
Gear Head's 4.500-inch spring...
Gear Head's 4.500-inch spring compressor was oiled up, and the Keith Black pistons were tapped in place.
The Scat 6.385-inch connecting...
The Scat 6.385-inch connecting rods feature ARP bolts.
Each rod cap nut was torqued...
Each rod cap nut was torqued to 85 lb-ft before installation. The crankshaft is an Eagle-forged unit with a 4.250-inch stroke.
The COMP Cams timing chain...
The COMP Cams timing chain lower gear can be installed three different ways, allowing for significant flexibility in engine timing. We put our gear on straight.
Don't forget the camshaft...
Don't forget the camshaft button, which removes endplay in the camshaft.