Don Terrill’s Speed-Talk

I was told by a reputable engine block builder that he recommended i use 3/4 groove main bearings to insure plenty of oil flow to rod bearings. I notice that clevite dont even make that bearing. I see where king and acl offer that bearing. Ive never used anything but clevite bearings in all my motors with no problem so i wonder if its just hype or what?

badbug3 wrote: ↑Tue Nov 19, 2019 2:47 pm I was told by a reputable engine block builder that he recommended i use 3/4 groove main bearings to insure plenty of oil flow to rod bearings. I notice that clevite dont even make that bearing. I see where king and acl offer that bearing. Ive never used anything but clevite bearings in all my motors with no problem so i wonder if its just hype or what?

Pure hype, and comes from a low understanding of oiling systems and how they work.

MythBusters

I prefer the 3/4 on my SBC's from a mental perspective but I have run both with nitrous and have never seen wear on either.

Some main bearings today are not even HALF groove but, only 160 degrees of the upper.

3/4 groove....... as compared to what?

modok wrote: ↑Tue Nov 19, 2019 7:56 pm 3/4 groove....... as compared to what?

Full circumference groove.

i've seen some inline 6 builders prefer 360 vs 180 to ensure rod bearing oil supply. I'm interested in the myth behind it

Ok, so....270 groove bearing in a v8? that's wierd


clevite studied it, and concluded 220 degrees of groove was best compromise. I agree.
If 220 degrees isn't enough for you, go full groove.
The 3/4 groove thing does not make sense for a v8, IMO

BTW show me a bearing with 3/4 groove.
probably 2/3 groove if you measure it

Will the be for circle track or Boat useage?

A groove might feed oil to the drilling in the journal for more degrees of rotation but it reduces the load bearing capacity of a bearing considerably. Think of how a bald tyre so easily loses contact with a wet road, then you put grooves in it and it cuts through the water and makes contact with the road again. Just the ticket for tyres; bad news for bearings.

I think the load bearing logic is why “they” nowadays groove a little less than 180 degrees of the bearing shell and all of it in the upper shell.

Are there some special considerations with BBC that would make grooving more than the top shell a smart idea?

People are down on cross drilling the mains, too, but for a low rpm engine it may not be such a stupid idea, it only causes issues with high rpms by my logic.

There are times when a full groove bearing is needed. To just say is stupid or not needed in a blanket statesman is foolish.

If the oiling system is inefficient then a full groove bearing will put some oil to the rods all the time.

ClassAct wrote: ↑Wed Nov 20, 2019 1:51 pm There are times when a full groove bearing is needed. To just say is stupid or not needed in a blanket statesman is foolish.

If the oiling system is inefficient then a full groove bearing will put some oil to the rods all the time.

Agreed, particularly when the crank oil timing is incorrect, it can bandaid the issue.