[A26B]

Originally Posted by Hib Halverson

I don't understand what prompted this research?

Has there been instances of the crank plugs "blowing" out?

In view of the GM plug being NLA, I started researching a suitable replacement to stock. In the course of that research, I found no "engineering standard" for drive/cup plug specifications, wall thickness, height, cup diameter, interference fit, etc. I ended up sourcing cup plugs from the UK in a 22mm size. Apart from a "seat of the pants" feel for the drive fit, I was still concerned about the performance of the plug in service, especially considering the critical service it performs.

Prompted by Screm's experience and Phil Wasinger's involvement in Screm's engine build, Phil undertook a comparative analysis test between 3 different plugs, the 22mm plug I sourced from the UK, the OEM GM plug and a Dorman SAE size plug. All three of those plugs differed in wall thickness, cup diameter & cup height. The objective being confirmation of the 22mm plug, especially since the GM plug is NLA.

Phil's work confirmed the 22mm plug suitability for the intended application.

I hope this sheds some light on the importance of the test results.