External oil pumps/roller cams/bronze gears

[wilf leek]

Jamo - you asked about hydraulic roller cams. As you know, I run a hydraulic roller in my (admittedly tiny) engine:

These are more likely to have longer lifter roller bearing life because:

1: They limit revs - the lifters are heavier than solid rollers plus you have the hydraulic pump-up issue.

2: Because they limit revs, any good engine builder would then put correspondingly weaker valve springs in - it is high revs that dictate high valve spring strengths to maintain control of the valve train. Lower spring weights means less stress on the lifter roller bearing.

3: Because of their self adjusting and zero-lash nature, the lifter roller doesn't see any impact hammering. (unless you rev the thing past the valve-float point). It is happier that way.

So, only go that route if you are happy with say, around 6000rpm tops. I know that someone will pop up and say that their hydraulic roller cam revs to 7500, but I would suspect that is a rare case.

I went the hydraulic roller route because I did not want to rev my engine past 6k, I wanted it to live a long time without going totally bonkers over it's internal components. I also don't like cam-break-in - it can be a real problem keeping an engine cool during that period once it is in the car.
Under-hood clearance issues on my car dictated a dual-plane inlet manifold, no point in building the rest of the engine to go much past 5500-6000. So I specced it accordingly.

Plus I like not having to adjust lash, ever.

JMH(AB)O