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OK, glad you "got it", it's really important. There is zero clearance when the lifter is pressurized with engine oil. I frankly forget what clearance there would be (with cam lobe down) without oil pressure, but I'd expect it would also be zero with an small (and depending on where you where in the 0.030 to 0.070 range) compression of the hydraulic section spring.

Here are a couple images of the gauge block method described above. There is a more detailed explanation of how it can be made and alternative method (described in the 1940 supplemental Manual) for checking depth described in my project thread.

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Just to avoid confusion in the future, note that though the principle and method of use are the same, the gauge blocks for the 356 engine and the 327/359 engine are different.

The 327/359 gauge is a simple cylinder and rests in the base of the bore of the cam follower; the 356 gauge has a lip and rests on the top of the follower.

Dear JD:

I've done dozens of these jobs and never used Tool
J-25whatever.

To obtain proper lifter preload the following procedure is pretty much universal for all zero lash motors including the Kettering V-8.

a) Remove the valves keeping them in numbered order.
b) Remove the hydraulic tappets keeping them in numbered order
c) Using solvent and lint free rags carfeully clean and remove all oil from the tappet bodies. These must be dry and free from any oil.
d) Clean the tappets in solvent as well.
e) Upon assembly the specified preload can now be obtained via valve stem grinding.
f) Upon final assembly the lifter bores can be primed for silence upon intial start up.

It is essential for optimum results that the grinding be carried out using equipment in good condition and personnel who understand the principles of boundary contact between metal surfaces.


Good luck.

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Tim, Thanks for an excellent explanation of the alternative method to using the plug gauge. By the way... where were you two years ago when my valve job was done?

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I can't tell you how many times I've read the '41 Preliminary Shop Manual, which has the same information on this subject as the '40, and completely missed the part about using the compressed lifter as the basis for setting clearance.

I guess it doesn't matter, I have a plug gauge now and it is more convenient (you don't have to hold the lifter in the compressed position with a screwdriver) and possibly more accurate.

And again, I start my day out learning something new about Packards.

Edit: It's interesting to me that in the 1946-1950 Shop Manual, the reference to using the compressed lifter has been dropped and only the plug gauge is mentioned as the basis for setting clearance.

Tim Cole writes:
"It is essential for optimum results that the grinding be carried out using equipment in good condition and personnel who understand the principles of boundary contact between metal surfaces."

That advice is the most important advice that can ever be given about any valve job on ANY engine. If the valve grinding is farmed out to a service provider then GOOD LUCK finding one that will follow Tim Coles advice whether the service provider is qualified or not. I've just been thru it too many damned times. This is especialy true on valves that have 'unusual' seat angles. I won't bore anyone anymore with details or reasons as to why that is true.

Just follow Tim Coles advice. BE SURE TO check the fit of the valves before assembly. ABSOLUTELY under NO CONDITIONS should the service provider of the valve grinding deliver the heads to the customer as assembled!!!

I believe that it neither is a mistake to use a gauge to check the basic setting (at least I can't see the mistake) nor to clean everything before follow up, accurate reassembling and measuring. Even the best hydraulic valve clearance, the priciest grinding instrument and the cleanest sealing surface don't make up for a wrong basic setting.

Dave (JD), I hope you will forgive me my objection, perhaps I didn't quite understand. Cleaning, using suitable tools and measuring aren't alternative methods. The same goes for the basically freedom from maintenance and the necessity for a correct basic setting. They depend on each other. It may looks like hairsplitting but the mentioned 0.030 inches are more than seven hairbreadths.

BTW, to convert hairbreadths into inches and vice versa use the below mentioned link. Unfortunately the link contains an apostrophe and therefore I can't embed it. Copy and paste it into your browsers address bar.

http://www.convertunits.com/from/hair's+breadth/to/inch

Here is the link:

<a href="http://www.convertunits.com/from/hair's+breadth/to/inch" target="_blank"> Hairbreadth to Inch Conversion</a>