I figure someone here will know the answer to this:
[perfunctory Healey content] We all know our cars have 'flat tappet'
lifter/tappet valve trains, while many of their contemporaries had
hydraulic or roller cams and tappets. It's always been a given that
flat, or roller, tappets were superior to hydraulic--for 'performance'
cars anyway--but why? Is it because flat/roller lifters allow finer,
more precise and more consistent valve operation, or because they're
cheaper? Otherwise, hydraulic lifters--which are also used in most
aircraft piston engines--don't require as much fiddling as flat/roller
tappets and presumably are less inclined to wipe cam lobes. It seems
rollers would be the best solution, but still require occasionally
fiddling, and generate lots of 'opinion pieces' as to how best to adjust
them.
What got me to thinking about this: A good friend just bought a gorgeous
BJ7 at Barrett-Jackson, along with a hot rod and a '62/3 'Vette (yes,
she has lots of money, or had lots of money until she bought a Healey
;). When I started it up--took me a while to realize that BJ7s still had
starter buttons--it had a very loud lifter knock. Before I started it, I
noticed there was what appeared to be brass shim stock covering the
rocker under the oil fill cap. I'm afraid: 1) the engine might have a
wiped cam lobe, which creates the loud 'tapping' noise and 2) the rocker
shaft may be worn, so someone put the shim stock over a rocker to
prevent an oil geyser when you open the filler cap with the engine
running. I can't think of a reason why these would be related, but who
knows? Also, when I popped the radiator cap it fell apart in three
pieces (cap, spring, and seal). It looked like it might have been the
original (I have a new one on order for her).
Bob
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