Inliners International Forums General Discussion Engines Mopar rod bearing 3967

Going through my part boxes and I came across a box of six nice rod bearings in Mopar part boxes, 3967 B 001. So I am guessing .001 under. I am not sure how I came to acquire them but any chance someone knows what these bearings are for? Would like to find a home for them as all I have are inline Chevy motors.

I don't know about the ones you have but if I remember correctly the Hudson rod swap into a GMC requires the narrowing of the rods and the use of Mopar rod bearings.

For those not familiar with a prior thread: a 292 (Gen-3) L6 connecting rod can be used to offset grind a 235/261 crank throw by reducing the journal diameter eccentrically from 2.311" (stock) to 2.100" (292), giving approximately 3/16" more stroke.
The same technique can be used on the G.M.C. 2.311" crank throw, reduced to the Hudson & Chrysler 25" L6 2.125" pin size.
In both cases the new rod length greatly affect the piston's compression distance and final deck height, the 6.76" 292 rod is shorter than the 6.8125" original (total change with 3/16" stroke added: -.04125"), the Hudson at 8.125" is far is longer than the original 7.000" (total change with 3/16" stroke added: +1.219").
The Chrysler rod was made in 3 lengths: 7.750", 7.875", & 8.000". Also possible: Pontiac 239" L6 at 7.5625".

So on the GMC with a Hudson rod you need to grind down to the Hudson 2.125 pin size. We can assume your GMC crank isnt perfect, so say you have a 2.300 dia to work with. To get to a 2.125 you can offset grind to (2.300-2.125)/2 = 0.0875 extra stroke. SO you go from a 7" to 8.125" rod gaining 1.125 plus the 0.0875" stroke gives 1.2125" higher pin height. Original Comperession height of 2.359 gets reduced to 1.1465...starting to look like a modern piston.

offset grind to (2.300-2.125) = 0.175 extra stroke

Great information , thanks. What is the wrist pin size on the Hudson rod? With a 4" bore (302) would any off the shelf pistons come close even with not doing the off set grind? Bore the piston to fit the rod or bush the rod?

Beater, the Hudson pin is still big at 31/32" or 0.9688, so needs modification. I have made my own bushings and bushed down to a SBC 0.927 pin, which is more than strong enough and lighter as well. I have pistons made by Traum and narrowed the rods myself. 850gr lighter per cylinder assembly
[img]https://photos.app.goo.gl/F9VUbFX3SAzgBcnJ8[/img] [img:left]https://photos.app.goo.gl/wSYjJmMpV2fXB8SR8[/img] [img]https://photos.app.goo.gl/YETMemeYyvc4YMFp8[/img]

That is really good information. Great pictures. Thanks for keeping this going!