Crack in Jack shaft block webbing

[gtrbg]

Due to a problem with my Datsun 5 speed while racing I just picked up a extra 5 speed, some misc parts and a U20 motor (looks like early 1968 with pre-smog heads (no air injector ports)). Engine spins so not seized and the heads and cam looks ok. Will need to get the block magnifluxed at some point if worthwhile but did notice a crack on the front bearing housing for the jack shaft that spins the distributor. See picture. Know they can pin, epoxy or sometimes weld cracks. Wondering if anyone has had experience trying to fix this? Not sure how much pressure is on the Jack shaft? Wonder it it got cracked from driving the split bearing in since crack is by the bearing split? If block is salvageable would like to do so to have an extra motor if not the rest of the parts look ok as spares in case I damage my existing motor.

[JT68]

You will want another block. Too bad. Pin/Epoxy/braze will do nothing. That is a stress crack, so a weld will fail as well-possibly make it even more likely to fail-and will distort the bore too. I don't know anyone who would build an engine around that block unless it was the last one in the world..... as the stress crack progresses, the bearing will lose it's press, spin, seize and blow up the front of the motor doing lots of additional (head) damage. Stop while you are ahead- transfer any good components to a fresh block. (and mag that one well) It's always a bummer to see a crack like that, but better that you did! j

[gtrbg]

Ok. Seems like sound advice. Possibly stupid question but do I need to find another U20 block or another type of Datsun block work?

[JT68]

If you are staying with U20, only a U20 block will work.

[Bwk2000]

I’ve seen examples of cold metal stitching used to effectively repair cracks/rust damage on blocks & heads. Not sure I would invest $$$ in attempting to repair a ‘any block will do’ example though - A numbers matching 1970 Chevelle SS, sure