Re: V12 Engine rebuild advice

Posted by Tim Cole On 2012/4/18 17:44:40

Dear rikki:

The reason I would balk at reusing old rod bearing shells is the issue of bearing crush. From a theoretical standpoint just unbolting rod bearings for inspection shouldn't be done because it can upset the crush fit of a bearing.

Anyway, it was my understanding that the EGGE merchandise always was the spun process.

I haven't spoken to Dale in quite awhile, but he was doing a run of Packard 12 motors. His bearings fit original rods and I don't think he is involved in connecting rod reconditioning. If you really don't want the babbited rods then the next move is to have your rods set up for a modern insert. What that entails is having your rods welded and machined so that the side clearance matches a modern engine the same way as a V-8. I'm not sure if they can resize the hole. The plan may become to fit inserts to your rods and then rebuild the crank.

Now purists will cry about not having babbited thrust surfaces on the connecting rod, but there are sound engineering principles involved in doing away with that and one of them involves why the Packard Company was having problems with rod bearing failure in the V-12. A narrower bearing is actually superior.

It depends on what you plan to do with the car. The laundry list can get pretty long and if your goal is occasional use under moderate service (45-50 mph) then that is a lot different than driving the thing from New York to Paris. One thing to put before this rod bearing stuff is having your oil pump bushings redone. They can suck air and cause oil foaming. Also if your cylinder heads have been milled to many times that is another issue. Yet another is the fact that these motor blocks are erroded and may not tolerate severe usage so spending a fortune on rod bearings may be a waste of money.

The future for the Packard 12 is that one day the water jackets will begin to seep coolant into the crankcase. So enjoy them while you can.