IML: different lifter reasons

["mike and linda sutton" <mikanlin62@xxxxxxxxxxx>]

Back when these engines were new, there was a running change in the lifter 
dimension for either the height overall or the plunger, I dont remember 
exactly what and when it was.  When I was in the parts arena we always 
showed two different lifters and two different push rods for the RB engines, 
I think it was 67 and earlier for one, 68 and later for the other.  Since 
you are installing a new cam you will of course get new lifters.  IF .. and 
this is an IF.....the lifter length is radically different from what was in 
the engine before, then the pushrod length may or may not be right for the 
combination.  This has nothing to do with the cam lift and duration specs, 
its purely a function of the pushrod and lifter combination being used.

You have to think of it this way, a hydraulic lifter is just basically a 
little oil pressure fed hydraulic cylinder that has the ability to 
automatically and exactly compensate for whatever valve lash is needed, no 
excessive clearance and no tight valves.  The little plunger in the lifter 
has only a certain amount of range it can travel thru, as I recall its 
somewhere around maybe 1/4 to 3/8 of an inch...I havent had to take a lifter 
apart in years and its something you seldom have to deal with.  The problem 
results if the pushrod being used with a particular lifter is too short and 
the little plunger isnt being pushed down in the lifter bore OR if the 
pushrod is way too long and the little plunger is pushed down and bottomed 
in the lifter.  IDEALLY the plunger should be about halfway down the lifter.

Most of the time this is never an issue, and seldom during a normal cam and 
lifter swap is it a problem.  The only real world practical thing one can do 
is after the cam and lifters are installed,  check one pushrod by installing 
a rocker arm and shaft on one side and see how much the lifter plunger goes 
down into the bore, then manually turn it thru a rotation and see what its 
doing.  By the way,  it is extremely easy to drop a lifter or a pushrod down 
the engine gallery after the cam is in place...and no, Im not going into 
detail about how I know this.  Magnets generally wont get them back out 
either.

A couple  other things...some people pre oil their lifters to get oil into 
the plungers, some just let the engine oil pressure do it during the first 
second or two of running and they will clatter a little bit.  I prefer to 
use a drill and a oil pump shaft extension and actually get oil under 
pressure to everything before I fire it up the first time, but thats just 
me.  Some people will just pull the plugs and crank the engine a bit until 
they see some oil pressure on the gauge.  Whatever you do, when the engine 
runs BE SURE to follow the cam makers directions on break in, if you let it 
idle before that cam is broken in youre not doing it any favors.  Make sure 
you put whatever break in lube  they specify on all the cam lobes and 
lifters.

Another new thing, apparently from some info on Allpar and other sources, 
the new modern ultra high tech oils out there have exhibited a tendancy to 
not provide proper anti wear properties on cams and lifters such as the 
aftermarket cams or cams with higher than stock spring rates.  This has been 
discussed on the MML as well, the reason appears to be the amount of zinc 
additives in the oil are rather low for emissions purposes.  Several people 
have posted to Allpar and the MML about using break in lubes such as the one 
GM offers, or just using oils such as the Delo 400 or Rotella multi weights 
that many current diesels use.  Just food for thought.

Mikey
62 Crown Coupe 


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