Crankshaft Cup Plug Test

[Jagdpanzer]

The question of how much faith we should have in our press in crankshaft cup plugs has been bugging me for awhile. I looked around but could not find any engineering information on the mechanical properties of cup plug pressure holding capabilities so I conducted the following pressure test to find out.

Here is the test fixture I turned out on the lathe from 4140 chrome molly steel material to use with the hydraulic shop press:



A 22mm tall sidewall cup plug supplied by Jerry's Gaskets pressed in the 22mm bore of the test fixture with Loctite 620 applied according to FSM instructions:



Set up on the shop press and pumped up to 300 psi test pressure:



Jerry's plug laughed at 300 psi for two hours so I switched to a 1000 psi pressure gauge and pumped it up to the to the full 1000 psi. Amazingly it still held!!.




Loctite 620 is some tough stuff. Take a look at force it took to press the plug out afterwards:



Conclusion: Anyone using Jerry's 22mm tall wall cup plugs properly installed can be fully confident those plugs are in to stay.

Up next is the Dorman 555-119 cup plug which cross references over to the GM 10067639 OEM plug