Re: valve job update

[jlandry@domain.elided (John A. Landry)]

In a brilliant stroke of genius, Kurt McDowell <gmcd@domain.elided> blurted
out:

>He says I should put in new original sixe mains in on the crankshaft without
>machinineing it to get the oil pressure up. This sound pretty dangourus to me.

This is not a completely bad suggestion with a few a few very important
precautions are observed.  First, let me say that the mains are not the
only cause of the oil pressure dropping on a high mileage engine.  Don't
forget you have a bunch of bearing surfaces (six?) on the camshaft and
eight connecting rods spitting out oil.  So this procedure may not help all
that much.  That being said, you just don't want to go slapping in new main
bearings without taking some measurements first.  As a minimum, you should
mic the crankshaft journals to see if they are within acceptable factory
tolerance specs for size and out-of-round condition.  Then, if you do find
them acceptable, you should be sure and verify the crank journal to new
bearing surface gap with Plastigage.  Too much gap means low oil pressure,
too little can mean insufficient lubrication.

>He also thinks I might as well replace my rings while im in there.
>If I do that, Then I have to worry about the rings seating properly.
>I dont burn any oil except at start-up.

Again, you just don't put in rings without getting the preliminaries out of
the way.  In order to put in new rings, you have to pull the pistons.  This
*will* require you to ream the ridges out of the cylinders.  Then you need
to take careful measurements of each cylinder to check for wear, out of
round, and taper.  If by some miracle the cylinders still fall within
factory tolerance limits (and I seriously doubt it), then you'd need to
break the glaze on each cylinder with a hone.  Then you can fit new rings
to the cylinder walls and then install them on the pistons, etc.

Sheez... by this time you've darn near rebuilt the engine, so why not go
all the way???

>My oil presssures not bad, Its about 5 or ten psi  at hot idle (depending
>onn how fast its idleing) and its at about 30psi on the highway. I'm using
>10-40oil.

Personally Grant, I wouldn't waste my money on trying to do the things you
mentioned unless I were going all the way with a full blown "pull the
motor" rebuild.  You'll be back having to mess with it again in a few
years.  Fixing one part of an old engine can cause unexpected problems in
another area.  For example, just doing a valve job on an old engine can
lead to *increased* oil consumption as the valves now seal better creating
more suction and blow-by around worn piston rings.

>Also I rember sombody saying that if you
>replace the lifters, then you must replace the cam. is this true? TIA

Absolutely correct!  You run a *great* risk of quickly wearing out a new
set of lifters by using an old cam and vice-versa.  The cam will have
certain odd wear patterns on the lobes which will not properly mate with
the new faces of the lifters.  The lifters will likely not properly rotate
either, which leads to rapid wear of both it and the cam lobe.  You could
wind up in a much worse situation in a few thousand miles than you started
with.

Just my $0.02, and I'm sure others will chime in too.

Take care,

John L.
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