cross-drilled crank bearing question

[haycait911]

a friend has a main bearing set that I'd like to use in my 3.0 rebuild. the center bearing shells have been machined with a groove for a cross-drilled crank. is there any harm in using them with a standard, not cross-drilled crank? doesn't seem to me that it would harm anything, but that's just a guess. any help much appreciated. thanks, Don.

[Flieger]

You will be loosing bearing area and I think you may have an excess of oil coming out of the center journal area and just dripping into the sump with nothing for the extra oil to do. I would just get the normal bearings if it were me. I would not want to mess around and take chances with such a crucial area when new bearings are cheap compared to a new engine.

[Henry Schmidt]

There will be negligible difference if you choose to use the grooved bearing.
The additional oiling in the cross drilled scenario comes from enlarging the oil passage that leads to the bearing itself.
The best application for these bearings would be to cross drill the crank, enlarge the fee passage and reap the benefits of consistent rod bearing oiling.
We cross drill each and every crank we install.

cheers

[kenikh]

On a related note, what if you have a crossdrilled crank, the oil passage mod, a grovved bearing AND a grooved crank main? Marine grooved my crank when I rebuilt it there and although I didn't ask for it, they did it anyway. I already had the bearing grooved, so am wondering if I should get a new bearing.

[Henry Schmidt]

Originally Posted by kenikh

On a related note, what if you have a crossdrilled crank, the oil passage mod, a grovved bearing AND a grooved crank main? Marine grooved my crank when I rebuilt it there and although I didn't ask for it, they did it anyway. I already had the bearing grooved, so am wondering if I should get a new bearing.

Run the bearing and crank combination with no worries. You'll be find.
Remember that if you want the full benftit from cross drilling you should also drill the main oil passage and oil supply hole in the bearing to a larger size.
Cheers

[lite75]

Henry,
Do you prefer a grooved crank or bearing?

[Henry Schmidt]

Grooving the crank eliminates the need for grooving a bearing so when we designed the Supertec SuperCrank we incorporated the groove but I see little benefit for choosing one over the other. I am not an engineer so I leave that analysis to them.
Note on the SuperCrank we fed each rod bearing from the corresponding main bearing allowing for even distribution across the entire crank.

[kenikh]

Originally Posted by Henry Schmidt

Run the bearing and crank combination with no worries. You'll be find.
Remember that if you want the full benftit from cross drilling you should also drill the main oil passage and oil supply hole in the bearing to a larger size.
Cheers

Thanks, Henry. I had always assumed that my Supertec/Burn Bros race prepped 930 oil pump would cover any loss in volume or pressure.

[Walt Fricke]

Henry

To what diameter should I open up my case oil passage to the center main bearing (and, of course, the hole in my already grooved bearing)?

I had not thought of this, so am glad I opened this post (and that you responded).

Walt

[Henry Schmidt]

Originally Posted by Walt Fricke

Henry

To what diameter should I open up my case oil passage to the center main bearing (and, of course, the hole in my already grooved bearing)?

I had not thought of this, so am glad I opened this post (and that you responded).

Walt

We use an extra long 6mm drill bit that is marked with tape at 80mm. This gets you all the way to the main oil galley.
Remember to drill the bearing shell to the same size.

[Walt Fricke]

Thank you.

Is the extra length for clearance for the drill motor (or press)? Maybe a drill bit extension holder would do the trick? I just ordered some extra long drill bits, but not anywhere near this size.

Or do I bite the bullet and get just what you have? I should go look at a case. I have drill bit stops, but I can see that the tape is the right deal when drilling into a concave surface you don't want to mess up.

Walt