when are 3/4 grooved main bearings needed for bbc ?

[tuffxf]

Exactly, well worded!☺

[russxr67]

Exactly, well worded!☺

Ha, you know what I’m talking about!

[Warp Speed]

In what case would a full groove be warranted, and how is it gonna fix a poor design?
What oil "timing issue" is it going to fix?

[mt-engines]

In what case would a full groove be warranted, and how is it gonna fix a poor design?
What oil "timing issue" is it going to fix?

i cant imagine it helping at startup to have to fill a crevace with oil before it gets to the bearing surface.

[rebelrouser]

I have seen this done and it seemed to work, how about grooving the bearing saddle in the block and cap, and then drilling a couple more small oiling holes in the main bearing? Similar to how a cam bearing is made in a SBC.
I run the 3/4 groove mains in my 440 mopar, and it always wears the bearings well, so I never messed with success.

[MELWAY]

In what case would a full groove be warranted, and how is it gonna fix a poor design?
What oil "timing issue" is it going to fix?

Ever played with stock ford cleveland cranks?

[Little Mouse]

Those damn idiot chrysler engineers, why in the hell did they not make there main bearings different on the 426 hemi that showed the other manufacturers how to run at 7600 rpm for several hours in nascar and win, not just blow up engines.

[Little Mouse]

Those damn idiot chrysler engineers, why in the hell did they not make there main bearings different with the 426 hemi that showed the other manufacturers how to run at 7600 rpm for several hours in nascar and win, not just blow up engines.

[Krooser]

I've seen guys complain about the SBM having bad oil timing issues, too. But mostly way over 7,000 rpms.

Comments?

[Warp Speed]

In what case would a full groove be warranted, and how is it gonna fix a poor design?
What oil "timing issue" is it going to fix?

Ever played with stock ford cleveland cranks?

Why the hell would I, or anyone for that matter really?!?
You can always fit this type of thing to some inefficient pos from yesteryear, but I would like to think we're all a little wiser these days!
Why do you think an LS can feed the rod bearings well, while flowing about half of the oil that you would have to to keep a Cleveland alive on a good day?
You see, longer bearing grooves being a positive, is kinda like people thinking that a tapered pushrod is stronger than a straight of the same max diameter. It seems plausible, but in reality, it is far from the truth!

[Warp Speed]

Those damn idiot chrysler engineers, why in the hell did they not make there main bearings different on the 426 hemi that showed the other manufacturers how to run at 7600 rpm for several hours in nascar and win, not just blow up engines.

I hope your not praising the fully grooved main bearing era! Lol

[MELWAY]

In what case would a full groove be warranted, and how is it gonna fix a poor design?
What oil "timing issue" is it going to fix?

Ever played with stock ford cleveland cranks?

Why the hell would I, or anyone for that matter really?!?
You can always fit this type of thing to some inefficient pos from yesteryear, but I would like to think we're all a little wiser these days!
Why do you think an LS can feed the rod bearings well, while flowing about half of the oil that you would have to to keep a Cleveland alive on a good day?
You see, longer bearing grooves being a positive, is kinda like people thinking that a tapered pushrod is stronger than a straight of the same max diameter. It seems plausible, but in reality, it is far from the truth!

I thought as much. But some blue oval die hards. Like to play with old stuff and I know of some that extra groove has helped a poor crank design

[GARY C]

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.

From what I can gather about how the main oil hole interacts with the 3/4 groove bearing it would be like cross drilling the crank, If it gives a steady flow of oil and pressure to the rods as oppose to a pulsing flow and pressure from opening and closing the oil passage at that transition I can't see where it would have a down side?... The load surface will clearly deal with at least a 300 shot of nitrous from near idle off the line on a foot break car and be in perfect condition after a season at around 1000 total hp moving a 3200 lb car.

[ptuomov]

Can someone explain to me, like to a fifth grader, what oiling problems can fully grooved main bearings fix? Too small crank oil passages, too large rod bearing clearances, mains not cross drilled in a low rpm application, or what?

[modok]

A full groove does reduce the load capacity of the bearing, for sure,.....but there are many cases when that's just fine.

A lot of big sixes and maybe this ford also, they have made the main bearing diameter very large to stiffen the crank, and bearing area is more than needed.

ALSO at much higher rpm, the upper shell may be just as heavily loaded as the bottom shell, so.... at that point, the only reason the upper shell has the groove is so it lines up with the feed hole, which, probably isn't in the ideal location either if you really want to think about it.