M42 Thrust Bearing Upgrade

[Rustee21]

I have been searching around a while now and can’t seem to find an upgraded m42 bearing set or just thrust bearing that would have 360 oil groove. All of them seem to have just little notches on the bottom half of the main bearings. I have read that you can use m50 bearings. I see how these resolve the 180 thrust surface to fill 360 but I don’t see it fixing the oiling issue. Please help!!! Am I just misunderstanding something?

[bmwman91]

To the best of my recollection, the "issue" was that the stock setup only had a 180° thrust surface. Unless this is a race engine, I do not think that the oiling groove is a concern. Even with the kind of poor stock setup, it mainly becomes an issue if you start the car with the clutch pedal depressed...full pressure plate force on the half shell with zero oil pressure is not good. There is zero good reason to start these cars with the clutch depressed.

Anyway, you can see about calling up Metric Mechanic since they know all about this, and I am sure that they would be more than happy to sell you a set. They detail this on page 10 in the linked PDF. You'd need to modify your main caps though.
https://metricmechanic.com/wp-conten...ne-Booklet.pdf

[Rustee21]

Yeah they use the m20 which is why they need to machine the end caps. Curious why the didint just go with the m50. I’ll give them a call and pick their brain. Thanks!

[wazzu70]

New bearing sets for the M42 have a 360 thrust bearing. Its just an M50 kit with less shells.

I don’t think there is really an issue with the M42 oiling groove. Manufacturers use less groove to reduce friction. If there was a real concern about not lubing the mains they wouldn't have reduced the groove and “updated” kits would be available. Its not worth worrying about IMO.

if you are concerned get the coated bearings. The coating helps retain oil and in cases of low oiling it can save your bacon.

[ForcedFirebird]

M42 bearings originally came with a single thrust shell (only the block side had a thrust, 3mm tang), but now when you order m42 bearings, they just send you m50 and you discard the rest - that in itself gives you an upgrade of the thrust. Early m20 has a 360° groove and 3mm tangs on top and bottom shells. Late m20 and all later engines up to the m54 (s54 has larger journals) have a single 3mm tab on the block and two 2mm tabs on the main bearing cap. I have never seen an oil groove in a shell with the two 2mm tangs, only the shells with a single 3mm (so, inherently early m20's all have 360° oiling).

[varg]

New bearing sets for the M42 have a 360 thrust bearing. Its just an M50 kit with less shells.

I don’t think there is really an issue with the M42 oiling groove. Manufacturers use less groove to reduce friction. If there was a real concern about not lubing the mains they wouldn't have reduced the groove and “updated” kits would be available. Its not worth worrying about IMO.

if you are concerned get the coated bearings. The coating helps retain oil and in cases of low oiling it can save your bacon.

I think the concern with the oiling groove is for the rod bearings not the mains. The logic is that a 360° main bearing groove keeps oil going to the rod bearing feed hole the whole time instead of being shut off for 90° of crank rotation, same logic behind crank mains being drilled on both sides in some applications. Whether this is necessary or even beneficial or not is debatable, that's just the argument. The bottom shell not having a groove improves its load bearing capability, since there is more bearing surface. Whether this groove or hole business is necessary when plenty of high revving car engines don't have it is the source of debate, K20s and F20s don't have 360° grooves or double drilled main journals, some of the motorcycle cranks I've seen had one or the other.