Date:         Fri, 8 Nov 1996 23:32:10 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         mholser@Adobe.COM (Malcolm Holser)
Subject:      Flat lifters

I stand corrected, that the VW lifters should be very slightly convex
when new.  Life is always a learning experience -- try to learn something
new each day.  I was (very politely) informed that they should have about
a 1-meter radius.  That's big, but it should be noticable.

All the ones I ever pulled from my engines aren't convex -- they're concave.

I *never* reuse lifters -- must have 50 of the dead things lying about
getting rusty.  Can't burn 'em like old cases...

If I ever do another typeI, it'll have hydraulic lifters.  New ones.

Besides being cheap, and making you actually look at your engine occasionally,
I recall that the *other* advantage of solid lifters was that at high rpm
(and high oil pressures) the hydraulics would "pump up", actually encouraging
the early floating of the valves.  High performance engines used solid lifters
to lessen the valvetrain moving mass and avoid the pump-up.  Does this still
happen?  Almost all of the race stuff seems to be hydraulic now, too, although
some *expensive* ones are solid (we're talking 'merikan V8 stuff).  And they
offer "variable duration" lifters from various sources.  What do these do,
and how do they work?

I also noted that some are advertised with "precision ground radius bottoms".
Chargrin.

Ok, a last question for you technophiles:  I still think that the offset of
the lifter on the cam rotates the lifter (I will believe that the radius does
too, either instead of or also) -- the point is the silly things rotate -- so
what happens with roller lifters?  They can't be allowed to rotate.  Do they
just wear fast (you know, racers don't really care...)?  How about roller 
rocker arms?  Do they still rotate the valves?  Any of this stuff make it into
VW's? (duh -- everthing makes it into VWs)

My airplane exhaust valves have mechanical rotators where the rocker sits,
very fancy.  Even without the fancy bits, though, these are $300 a pop.
Vanbondo take note: don't start restoring a plane! 

malcolm