Packard Forum Index » Pre-War (1899-1942)

Feeler gauge between the valve tip and adjusting screw on one of these just didn't feel right.

Tip of the valve looked like it was disappearing into the adjusting screw.

The top of the adjusting screw was worn 1/8" deep!

Never seen this much wear, poor heat treating job on the screw, lower hardness?

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Looking closely at the surface finish of the screw and locknut, they appear to be substitute (non OEM) parts, perhaps just hardware store quality. You can do a quickie hardness test with a file.

PS - question, if the supposition is that the depression in the screw was formed by the pounding of the valve stem, where did the displaced metal go?

Is the thread special or could the screw on the right be something like a grade 2 from a hardware store.

Pm me your address and we will send you the bolt and nut, all same 28-39
big 8's.

Thanks
James From
Kanter Auto Products

I appreciate the feedback and offer. I did have a few spares so I could swap it out.

I'm going to bring them to work and take a few hardness strikes. The machine at work can read HRA, B and C hardness scales.

If I can borrow the XRF, I can also analyze elemental composition. For those not familiar with the XRF, it is a hand held device you hold against the part and the device displays the elemental composition of the part.

https://www.bruker.com/products/x-ray- ... d-xrf/metal-analysis.html

Will report back on findings.

I believe the thread is a standard 3/8-24 UNF.

Good point, looks like there is a difference in finish. Low quality, non Packard part?

Bottom of the offending tappet looked OK, so load wasn't excessive.

Where did the metal go, it wore away? Abrasive wear vs. cold forming.

Three hardness tests on both showed no significant difference.
Based on the similarity between the measurements I believe the worn bolt is an OEM part.

The bottom of the tappet with the worn bolt was worn concave and the OAL was shorter.

A few addition close up pictures show the wear on the top of the bolt head.

Hardness (HRA)
Not Worn Worn
56.32 52.23
54.44 59.61
58.21 57.78

Bolt Head Across Flats
.562 .562

Bolt Head Length
.204 .205

Tappet Body Length
2.443 2.435

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