BB chevy main bearings ?

[greg fulk]

1/2 groove or 3/4...upper only or upper & lower groove? .060 over 396 crank is .020 under car is street strip maybe pure stock IHRA (that would be down the road though)What would be best to use?

[Alan Roehrich]

I use coated King 270 degree groove main bearings. Hundreds of passes later, my bearings, rod and main, look like new. I use King rod bearings, too. H.M. Elliott does all of my coating, although I buy my DuraBond cam bearings already coated.

[Mike Taylor 3601]

1/2 or 3/4 either should be fine 3/4 groove will oil rod a little longer than half. Full groove will oil rod all the time,which is same thing cross drilling crank will do.
Mike Taylor 3601

[CFMCNC]

Full grooved will deplete the hydrodynamic oil wedge between the shaft and bearing surface.Bill C.

[Reed Granrt]

Originally Posted by CFMCNC

Full grooved will deplete the hydrodynamic oil wedge between the shaft and bearing surface.Bill C.

This is a double edge sword. One will help the rods and one will help the mains.
The more groove you put in the main bearing, the more you oil the rod but ALSO the more groove you run, the more hydrodynamic wedge you take from the mains. Contrary to what most people think, the loss of the wedge may not hurt the main bearing but the crankshaft no longer rides in the center of the wedge that you work so hard to develop. Loosing the wedge will cause the crank to move upwards in the bearing and should/could result in more friction in running in the main bearing. The increase in friction should/could cause elevated oil temps. You may never see the elevated temp from such a short run, but needless to say it is there. If you are having no rod bearing issues, then go down on the groove as this will help establish the wedge better. I dont know this to be true but sure sounds good any how. HeHe
reed

[BlueOval Ralph]

If cross drilling and rod drilling is not done at the correct angle for the stroke it ( the cross drilling) will shut oilling to the rods at about 7600 and above.

Originally Posted by Mike Taylor 3601

1/2 or 3/4 either should be fine 3/4 groove will oil rod a little longer than half. Full groove will oil rod all the time,which is same thing cross drilling crank will do.
Mike Taylor 3601

[Reed Granrt]

Originally Posted by BlueOval Ralph

If cross drilling and rod drilling is not done at the correct angle for the stroke it ( the cross drilling) will shut oilling to the rods at about 7600 and above.

Hey yall, please dont think I feel I am a know it all on this subject BUT I wont to express/show an observation.. B O Ralph--I feel that this is one reason that there has been many companies to no longer provide cross drilling, the other reason is that it weakens the crank. Most cracks or breaks start from bad radius or hole. With today oils, if you can establish the wedge, it will remain for one revolution until the oil hole reappears. If you have a groove, you never really got a wedge on the main. The reduction in friction comes from the crank riding on the oil molecules and not on the film. Yes you may loose the wedge but you "hopefully" will ride on the film, but riding on the film is not as friction-less as riding in the middle of the wedge. On the firing stroke, I feel you want the mains and the rods to be in the wedge and not on just film. There is only 3 areas in a motor that you can utilize a wedge---rod bearings, main bearings, and cam bearings. Every place else is on a film. Proper use of the wedge will make it almost friction-less(most synthetics), but a film only lessens the load. This is why synthetics, in this instance, is less friction. The oil molecules are like marbles. Man made synthetics have all marbles the same size. Most mineral base oils have all different size marbles, therefore the crank runs on different size marbles and is point contact loaded (it only rides on the large marbles).
I said enough. Got to work see yall
reed