Dick T wrote,
----------------------
>When you state that regrinding the lifter base to obtain the "concave"
>affect, this is not correct. Due to being positoned off-center from
the
>cam lobe, the lifter is expected to be rotated by the cam lobe. This
>results in the lifter receiving equal wear all around it's base but
also
>gives the lifter a "concave" wear pattern which we would NOT want to
>intentionally put back onto the lifter.
For whatever reason that it may seem, new lifters excluding flat
tappet lifters, have a slight concave surface to them.
Crower cams specifies that it should be a minimum of 2 thousanths
of an inch high in the center relative to the outsides.
This amount of concavity could be considered "invisible", but
for whatever reason, it is there, and with a straight edge across
a new set, you will see it too.
>The cam lobe is ground dead flat (not rounded in any way) and we need a
>dead flat lifter to carry the extreme pressures present all the way
across
>the cam lobe evenly. After long use, the lifter and lobe will of
course
>have worn into a slightly curved shape but they MUST start out flat
when
>new .
This is true, but it is also interesting trivia to know that most
regrinders put an intentional angle on the cam lobe making the cam
slightly non-perpendiculare to the lifter.
This info also comes alla Crower.
Tomorrow, I'll bring in my cam litterature from Crower, and Crane.
Then I'll quote the literature verbatum, and maybe have an
explicable reason for thier madness.
>I found it also interesting that you "never saw Alpine lifters without
>pits". Well of course we all have seen pits but I would say that most
>lifters I have seen were without pits and could be refaced and made
>serviceable again. Hmmm...wonder where all the badly pitted Alpine
lifters
>have gone to?
Well obviously they are going to me!
But seriously, perhaps the previous owners of the motor that I have
built
floated the valves or something, but the fact remains that I have a box
full of pitted lifters (24 or so).
On a similar note, in my current motor, I put a good hot cam in it
earlier this year. The old lifters came out, which only had 2000 or so
miles. 2 of the 8 lifters were pitted, and one had a concentric groove
worn into the bottom of the lifter. the remaining lifters looked great.
>Due to where this exists it would not be seen by the eye but by the use
of
>some machinists "blueing" called Prussian Blue paste, we can apply the
blue
>to degreased parts, assemble them and note the area of contact.
Its pretty obvious where the contact point is on the broken in pieces,
its all across the ball and cup, because the whole thing is shiny as
and smooth as a mirror.
The point here is that depending upon the way that the parts break
in together, the parts can and do end up with slight differences in
their interface with connecting parts with respect to other parts.
These minor differences break in eventually, but as they do,
the lash goes up.
I used new lifters, with used pushrods, and a new set of
rockers. The motor has had the valves adjusted 3 times,
and it looks like I am gonna have to do it again soon.
Each time I adjust it, the adjustments get smaller, but it
is always to lake up the lash, not the other waw around.
>Re. the cost of case hardening lifter base if major regrind was done
and
>too much metal had to be removed....The lifter is cast iron, not steel
and
>all that needs to be done is to buy some gunsmiths hardening powder and
the
>one I use is called Casinet from Brownells catalog.
>The lifter base is simply heated to a red glow with a torch and the
powder
>applied . It provides a high carbon case hardening of unknown depth but
>then we don't need more than a few thou. So I feel this is so cheap
that
>anyone could afford a couple bucks for the powder and this makes
>rehardening lifter bases not as costly, as you suggested.
No comment here, I tried to get some parts hardened a while back,
and considered hardening some of the new, but broken in lifters
I removed from the motor.
The cost was $150 for 8 rockers and 5 lifters.
>one I use is called Casinet from Brownells catalog.
If this stuff really works, it sounds like it could be really usefull.
BTW, I didnt know you could harden cast iron.
Jarrid
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 09:55:59 CDT