Reply To: I may be going over to the dark side……

[Gregory Long]

To James Chase: Thank you for an engineering explanation for the Rube Goldberg lifter designs in the Packard engines. It kinda-sorta makes sense, but I’m still amazed at the extent and degree of ‘going overboard’ that Packard went with this design.

An example is in the V12 ‘silencers’ The V12 roller has TWO layers of roller bearings. The roller design from the middle out: the central shaft is first, a set of rollers ride on this shaft, then a thin roller, like a piece of precision steel tubing goes over the inner rollers. Then on the outside of this thin roller is a second layer of roller bearings. And finally the outer thicker roller that rides on the cam lobe.

So each roller assembly has two layers of roller bearings. Each layer of roller bearings must be ground to very precise tolerances, and the rollers, rings and shaft have to be a high quality hardened steel. This is an amazing degree of over-kill, that probably caused and created a lot of maintenance and repair, instead of creating longevity. I know that the silencer assemblies for the V12 are a big stumbling block for engine rebuilders.. Most make a single new brass bushing to replace the double layer of roller bearings. The rust, wear and excess tolerances in the worn out roller bearings are pretty much a given for a Packard engine rebuild.

The Packard 8 has ‘only’ a single roller bearing in each lifter roller.

NOW in contrast, the Pierce Series 80/81 does have a direct acting roller riding on the cam lobe, and there is some side thrust on the lifter and lifter guide assembly. But the lifter guide assemblies are simple cast iron items, that usually need replacement due to breakage rather than due to wear. The breakage is done by someone loosening or tightening the lock nuts on the lifter adjusting screws, which will break the roller slot guides off the assembly.

Breakage, not wear has prompted a PAS member to reproduce the lifter guide assemblies.

I’ve only seen a few lifter guide assemblies that are too worn to go back into service, but I’ve never seen a Packard that didn’t need a full replacement of the lifter rollers and bearings.

The Series 80/81 rollers are a hard steel roller riding on a hard steel pins. The pins are drilled for an oil passageway, and cross drilled at the roller to let the oil onto the roller/pin oil space. The only problem occurs with infrequent oil changes and the oil drilling gets clogged with sludge.

Our Pierce camshafts don’t seem to suffer any excess wear from the rollers. Only from rust broken lifter guide assemblies letting the roller turn sideways.

I definitely like the simplicity of the Pierce designs.

The 8 and V12 Pierce engines have such generous camshaft lobe width, that if the engine is not allowed to sit and rust, the cam and flat tappet lifters usually don’t have excess wear. And ZDDP was not needed then nor is is needed now, the valve spring pressures are quite low in our low rpm engines so the high pressure anti-wear characteristics of ZDDP are not needed.

Greg Long