On 2002-04-16 21:36, Nastystang wrote:
reduced wear on valves, rockers, guides.
This part is totally untrue.
The extremely fast acceleration rates and high lifts of roller (and their required mega stiff valve springs) put incredible loads on the whole valvetrain. Valves, rockers and guides don't live as long as they would with a flat tappet cam. Solid not only jerk the valve off the seat, they also slam it back down... which has a way of wearing a valve job out pronto. Rollers are made of steel instead of iron, like flat tappet cams. Therefore, they are incompatible with the iron gears of most distributers. With these cams, sacrificial bronze gears are used. These wear quickly, and must be changed about as often as the oil... As an option, some cams are available with pressed on iron gears.
Solid roller lifters don't have that long of a lifespan with extended use. They wear out, and if they turn sideways, there go the cam lobes. It's common practice to install screens in the lifter valley to catch any roller parts that happen to get spilled in event of failure. On Fords, the cam is just driven by a small pin that hooks it to a top timing gear. Since the forces required to drive big rollers (and their stiff springs) is immense, the pins often break... when this happens, the valves stop moving and get hammered by the pistons, killing the engine. Some will 'double pin' the cams to avoid this.
Solid rollers are for top level racing. Stick with Hydraulic rollers and flat tappets for extended use.
Some 'street' solid rollers aren't quite as aggressive as the others, but aren't quite as effective either.
Good Luck!
_________________
Mike Burch, 66 mustang real street
302 4-speed 289 heads, 10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
<font size=-1>[ This Message was edited by: n2omike on 4/17/02 9:57am ]</font>