> I've been scouring this list for some time now and have found that it
> contains very little information (if any!) relating to hydraulic roller
cams
> that can be used with the Buick/Rover alloy V8 (or its derivatives). This
> seems a little strange (if they are, in fact available), as I would
suspect
> that this is definately an area that would be of concern to the
performance
> enhancement for these engines - especially the bigger capacity variants of
> these motors that are close to 5.0L.
Hydraulic roller cams and lifters have drawbacks as well. Besides
cost (typically 3+ times as much for an aftermarket conversion kit), they
are considerably heavier and require stiffer valve springs. The heavier
weight
implies a lower rev limit. Above a certain spring rate, hydraulic roller
lifters
will pump up (oil gets squeezed out). In a 351C (with heavy 2.19"/1.71"
diameter valves), available hydraulic roller lifters limit at around 6200
rpm.
Hydraulic flat tappets can go to 7000 rpm.
> all this adding up to improved performance. The Australian Commodore V6
> (Buick variant) is one such engine which benefits enormously from the
> advantages of an OEM hydraulic roller camshaft - having an almost flat
> torque curve throughout the entire rev range, resulting in a very
tractable
> engine.
OEM's went to hydraulic roller lifters/cams primarily for warranty and
emissions
reasons. There's no cam break-in period required and very long cam life.
Performance isn't necessarily any better. The cam profiles used by OEM's
are
usually not any more aggressive than flat tappet cams. The flat torque
curve you
mention is probably more due to EFI intake manifolding and computer modeling
(better match of all components).
>A high capacity Buick/Rover V8 however, has very good low end torque
> but dissapointing top-end power due to standard heads inability to flow
> sufficiently for the increased engine capacity. A hydraulic roller cam
could
> compensate for this by increasing the flow but not necessarily the cam
> duration, resulting in a flexable engine throughout the operational rev
> range with good idle characteristics. Sound too good to be true? Believe
it!
Since the stock heads reach peak flow at a relatively low lift, any extra
lift
generated by a hydraulic roller cam would be largely wasted.
> ......and finally to my questions: Is there a hydraulic roller cam
available
> for the Buick/Rover V8? Who is the supplier and at what cost? Can one of
> these cams be fitted to this motor or are the modifications required to
the
> block too extensive (i.e. lifter gallery oil passages)?
Not that I'm aware. I have some information (old magazine article) on a
solid roller set up, though. Do the latest Rover V8's still use flat tappet
cams? Another avenue to investigate would be mushroom lifters.
Dan Jones
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