-----Original Message-----
From: Jones, Daniel C <Daniel.Jones@MW.Boeing.com>
To: Aluminum V8 List (Buick/Rover) <buick-rover-v8@autox.team.net>
Cc: mgb-v8@autox.team.net <mgb-v8@autox.team.net>
Date: Friday, 25 February 2000 6:44
Subject: RE: Hydraulic roller camshafts
>> 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.
Sure - but I'm talking about a street motor here used for everyday driving;
not a speed boat or drag car engine. The long stroke (3.4 - 3.5") of a 5.0L
engine would make these revs fairly prohibitive anyway.
>
>> 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.
Flat tappet cams are alot cheaper to produce by manufactures than roller
cams. There's a lot more cost involved in a roller setup due to the
component parts being more complex. There's not a lot that can go wrong with
a good flat tappet cam setup so, I doubt that manufactures would switch to a
roller cam for warranty reasons.I would expect that emissions had more to do
with it than anything else you mention.
>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).
Manufactures use these (roller) cams because the motor can breathe as well
as a motor that uses an aggresive (flat tappet cam) profile) while still
maintaining the smooth idle and road manners of a motor that uses a stock
profile cam.
>
>>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.
The extra lift would allow time for the cylinder to fill more completely
over a longer time period (at max flow) and would certainly not be 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.
Yes - they still use flat tappet cams as far as I am aware.
>
>Dan Jones
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