Re: 1925 Packard information

Posted by Owen_Dyneto On 2009/5/10 14:03:13

My ancient AC spark plug catalog show two different thread size plugs used in Packard 1924 thru 1931:

For 7/8 NPT thread, AC 78
For 18 mm, AC 86.
Gap on either, 0.025 inch.

You'll have to work out the conversion #s to modern plugs once you ascertain the thread size.

As to oil, I'd be tempted to stick the viscosity that Packard recommended originally, at least as a starting point. There's often a temptation to use heavier oils on older engines, and while it may quiet things down a bit and perhaps increase pressure, the downside is that it's poorer at transfering heat which is an important consideration especially with babbitt poured bearings. Whatever oil you use, before you put any significant time on the engine, drop the oil pan and clean it and the pump intake screen at a minimum.