> What are the limitations on RPM, (or anything else I should worry about) with a Hyd roller.
To my knowledge, my buddy Marc Arnold had one of the fastest normally
aspirated, fuel-injected, hydraulic roller-cammed 5.0L-based Fox body
Mustangs in the country. He's a guinea pig for Anderson Ford Motorsports
and ran a series of AFM's "Hi Rev" hydraulic roller lobes and turning
nearly 9000 RPM through the traps with a hydraulic roller cam and
lifters (real hydraulic lifters, not modified internally to be solid).
The car started out as new street car and evolved into a 9 second drag
race only vehicle. He started out using steel valves and Ford OEM lifters
and dog bones, then moved to Crane link bar lifters and later to titanium
valves before moving on to a solid roller cam.
When he switched to the solid roller cam, I borrowed a set of his one season
old Crane link bar lifters to mock up an engine and some of the lifter bodies
were scored. Marc mentioned the seats in the heads were also showing some
wear indicating some valvetrain bounce when he ventured into the 9000 RPM
region. IIRC, he has some dyno data showing a pretty ratty curve after
about 8800 RPM. Everything was tested on Anderson's dynojet and Marc has
documented some of his engine combos and dyno pulls here: http://the-arnolds.net/Cobra/index.htm
> Crane gives a rev range out to 7200rpm on the large HR's. But most other
> companies only show about 6500rpm.
In general, hydraulic roller lifters need some help to turn a lot of
RPM. Heavy valves and large rocker ratios only makes things harder but
there are several things that can help extend the RPM range:
1. Better lifters (e.g. Crane link bars)
2. Limited travel lifters
3. Special hydraulic roller oil
4. Better springs and lighter retainers (beehives with nickel
5. Lighter valves (titanium or Ferrea hollow stem steel)
6. High RPM lobe profiles
Anderson did a bunch of testing to find hydraulic roller lobes that are
stable at higher RPM and Marc ran a bunch of different cams in his engine.
Some cam grinders will note which lobes are suitable for higher RPM.
For instance, Bullet lists their master lobes by three letter prefix.
The second letter is either T for torque/low RPM limit or R indicating
the lobe is suitable for high RPM and/or high ratio rocker arms.