Nice to be clean and all ... but some of us would like to add a degree of
reliability that isn't there otherwise. Vintage is becoming prohibitive due
to the need for "period" parts. That's all fine and good for those with an
unlimited budget ... for the rest of us, it means that we can't play.
Should we allow roller rockers? ... I don't know, but racing an early '60's
BMC car is challenging at best and painful when the rules say "build it to
1964 specs." When I need 2-3 engines to get through a season at $6-8K each,
I think we've lost the point on amateur racing. If having fun is no longer
a primary objective, then we're on the right track.
-----Original Message-----
From: Brian Evans <brian@uunet.ca>
To: vintage-race@autox.team.net <vintage-race@autox.team.net>
Date: Wednesday, January 20, 1999 2:44 PM
Subject: Re: Roller rocker posting for fellow racer
>
>>
>>A-series engines are perhaps a little different that some others, because
>the head design limits breathing so much. I'll go with the original poster
>that the advantages and disadvantages to an A-series are almost even, in a
>given engine build. A-series engines don't respond well to lots of lift,
>but they do respond to fast acceleration of the valve, and to lots of
>duration at the lift that works (about .350"). Fast acceleration of the
>valve results in lots of side thrust with the A-series rocker geometry, so
>the guides wear fast. So I think that it would be correct to say that
>roller rockers wouldn't give more performance using a fast-ramped cam, and
>would give better guide life than normal rockers. BUT by using a cam that
>has lower acceleration you can have acceptable guide life with normal
>rockers ( and yes, even better life with roller rockers) at the expense of
>performance. And that's the whole point of not using newer technology.
Not
>allowing the roller rockers for the vast majority of racers is moot - they
>don't take full advantage of what they can do under the rules for either
>performance OR reliability, so who cares? We don't, and shouldn't allow
>them simply because they weren't available in the period AND because they
do
>have increased performance potential for all engines.
>>
>>Remember that there's always a performance/reliability ratio that decides
>what we do to get faster. Colin Chapman used to say that he wanted his cars
>to fail on the cool-down lap, then he knew that he'd gotten the equation
right.
>>
>>Cheers, Brian
>>
>>
>>
>>At 01:09 PM 1/20/99 -0500, you wrote:
>>>
>>>In a message dated 1/20/99 12:07:39 AM, PaceCars@aol.com wrote:
>>>
>>><<Roller rockers are not a performance advantage for A series motors.
What
>>>roller rockers do is give you longer valve guide life, due to less side
thrust
>>>on the valves. Roller rockers are noticeably heavier than non-rollers,
so if
>>>you want to run high revs, non-rollers are probably superior.>>
>>>-- that may be true IF there are no other changes to the motor. As I
>>>understand it (and I am no expert on BMC motors) the roller rockers allow
the
>>>use of other parts which can greatly enhance performance.
>>>
>>> <<Many of the fast guys in SCCA run non-rollers (Comptune sells his own
>>>version of non-rollers) due to less valve train mass. >>
>>>-- and how often do these "fast guys" rebuild the motor. I've heard they
run
>>>such radical specifications and high rpm that they install new crank
bearings
>>>every other session. I suppose if someone in vintage wanted to do that
with a
>>>non-roller motor and vintage legal parts (whatever that means these
days), I
>>>could not complain. I also would not envy anyone doing 3 or 4 engine
rebuilds
>>>every weekend as part of normal maintenance!
>>>
>>> Sorry, I will not be convinced that roller rockers do not improve
performance
>>>by allowing higher rpm and more aggressive cams and other performance
parts.
>>>
>>> Cheers, Doug Meis
>>> (Of course it's easy for me bitch about roller rockers when I've got
overhead
>>>cams AND a roller crankshaft)
>>>
>>>
>>
>
>
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