Packard Forum Index » V-8 (1955-56)

Quote:
<p>
Jack, do you have a special jig to reface the rocker tips since the radius on the tip must be maintained. On some of the worn tips I have, a considerable amount of material would have to be removed. This would probably remove the surface hardening which would accelerate follow-on tip wear.
</p>
<p>Craig</p>

Thoughts and observations on valve train wear and adjustments:

1. Of the dozens of Packard V8s I've torn down, only one had terminal cam lobe and lifter wear. On most of the others, the cam and lifters could have been cleaned and re-used as per the bad old days shadetree rings-and-valve regrind rebuilds.

2. The Packard V8 valve train was designed with an acceptable assembled measurement of .050"-.210", or .160" of hydraulic lifter travel. No conceivable combination of normal wear and reconditioning would exceed this range of automatic compensation, if the work is done correctly.

3. "Stemming" is using a special micrometer to measure the distance from the valve spring retainer lower face to the head spring seat pocket. The measurements are compared to standard spec. Any over-length is removed by grinding the valve stem tip, thus adjusting the height of the valve stem to a to compensate for refacing of used valves, cutting used seats or new hard seats. This is a standard operation in any quality valve and head work and keeps the valve train length identical, spring pressure identical and both close to original design.

4. Rocker arm tips are one of the most serious wear points on a Packard V8. The tips should be refaced as a standard procedure on any Packard V8 rebuild. The amount of stock removed from the rocker tips will be compensated by that milled from the head gasket surface. Again, milling the head is a standard function of a valve job. Thus, the valve train length remains close to original design.

5. Most Packard V8 lifter noise is caused not by wear of the lifter face itself, but the cumulative loss of oil pressure from wear of rocker arms bores, lifter bores, cam, main and rod bearings and the oil pump itself.

thnx, jack vines

We need to distinguish between adjustable valve lash (mechanical lifter adjustment [hydraulic lifters make such systems "zero lash"]), and adjustments sometimes necessary after grinding valves and faces, milling heads and decking blocks, etc. to get the velve to static lifter dimension back into the range of accomodation of the hydraulic plunger. Though this is a common procedure on the L-head engines with hydraulic lifters, it is also occasionally required on hydraulic lifter-equipped OHV engines as well.

TRue. But most engines prior to the HP revolution of 1955 were only good for about 40K to 50K miles until required rings and a valve grind anyway and most likely bearings or shimming. In the ford plymouth and chevy class the transmissions/clutch were only good for maybe only 40K to 50K miles and it's not like they were driving those cars at SUSTAINED interstate speeds or any kindof conditions resembling modern demand, not even of the late 50's.

Sure, even 6 cylinder AMC up thru the early 80's that i know of had no valve lash adjustment and the head had to be removed to change the lifters, another BAD design for service convenience.

But what are we talking here???? F, Chev and plymouth or Packard built by "Master Engine Builders"????

What about engines in the same class as the Packard V8 of the mid 50's????? What about Lincoln, Chysler Imperial, Cadillac/Buick V8's and the like???? Did they have adjustable valve lash????

owen, that is definately true for smaller L heads, including lawnmowers which have NO adjustments and solid lifters. you get your adjustments in by valve seat grinding or grinding the stem.

Isn't it pretty analagous to the L-head engines with hydraulic lifters; when the seats were ground deeply enough you had to grind a bit off the valve stems to bring the system back into the range of accomodation of the lifters? Not that I've ever done a V8, but I'd think that's a standard part of the service procedure.

Somewhere about 60K to 70K miles the lifters will get noisy in any engine due to wear, dirt etc. Especialy of the pre-1980's era. Replace the lifters????? WHY??? because they are worn???? They usualy wear at the base that rubs the cam. On the engines with adjustable push rods or rockers one can simply give the adjuster nut a quick 1/4 turn and noise problem solved for another 20k to 30k miles until the bottom of the lifter wears thru.

It's not like Packard was offering engines for the commoners of the world. They were supposed to be offering quality, long life and service.

Build a new or newly rebuilt engine and ship it out with a 3 year or 30K mile warranty is one thing. Run one 150K miles and squeeze another 50k out it is another.

To a great extent u're rite. I'm tempted to retract my statemnt. I suppose the best answer to your question is another question:

Why does the service manual on p23 of engine section define a valve lash check procedure???? Incidently, it gives NO correction procedure either. No over or under length pushrods listed in the parts cataloug???? I believe Ford offered such over and under length pushrods for their engines.

Quote:

What problems have we encountered which would have been solved by adjustable rocker arms?

FWIW, few-to-none of the OHV engines designed since Packard offered valve adjustment. Of those few who did, some, such as the small block Ford, in its' later redesign went to fixed valve train. The experience was most mechanics and owners did more harm than good with adjustments.

thnx, jack vines

No adjustment. HOWEVER this assumes correct lifters are in the engine. There are 2wo different MoPar lifters that will FIT the lifter hole but only ONE of the MoPar lifters will work correctly. The other MoPar lifter has a push rod seat that sets too high.

SO, assuming that the lifters are Packard lifters or the correct MoPar lifter then NO adjustement is neded. IF the tall MoPar lifter is unwittingly used then it is quite possible that they either will not pump up or may just hang the valves slightly open.

Look in the service manual. There is a procedure outlining the anount of collapse that each lifter should have. About 2/10" minimum if i recall correctly.

ULTIMATELY tho. There is NO adjustment for the PAckard V8 valve lash. Definately a poor engineering decision on the part of the "Master Engine Builders" of Packard.