Fully groves mains

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I've been known to buy two sets of main shells to get full grooves. I also file the oil notch in rod shells that a lot of modern bearings lack. I would rather over oil the cam than wipe it through prolonged idling.
 
I buy em that way, but have only built big and small blocks. Sounds like the /6 ones ain't available? Man, I've had MANY of those Leaning Tower of Powers! Never had to rebuild one... although I killed one, on i-75, darn exhaust manifold was GLOWING Like coals in a smoker..IIRC, oil dipstick....
 
12many said:
Influence of Grooved Main Bearings on Performance
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If you read the article, it states by full grooving it is bad for the main bearing, but good for the rod bearing. In my case/application, I had issues with rod bearing failure (particuly #5). The mains on a slant six, are the same size as a Hemi. Also rotation speed of the crank, has an effect. Once I started doing full groove mains, I had no more bearing issues, and I have turned some my 170CID engines 7,000 rpm. I am not arguing for or against full groove mains. Just stating what worked for me (in slant sixes), for over 40 years.
PS: I also do not believe in high volume oil pumps on the slant six.
PPS: your results may vary
 
What would worry me [ & why I wouldn't do it at home ] is how do you know if you have raised a burr? Cutting, grinding metal, raises the edge. The brg clearance is a little over 0.001" if you are running the customary 0.0025" gap. Any metal protruding above the surface will scratch the crank & I know of no way of the home builder accurately assessing that small amount.
 
Bewy said:
What would worry me [ & why I wouldn't do it at home ] is how do you know if you have raised a burr? Cutting, grinding metal, raises the edge. The brg clearance is a little over 0.001" if you are running the customary 0.0025" gap. Any metal protruding above the surface will scratch the crank & I know of no way of the home builder accurately assessing that small amount.
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The bearing material is much softer than the crank. A vertical burr on a main bearing will not scratch a crank.

Regardless, good machining practices includes de-burring after cutting. Lightly rubbing the two side edges of the cut in groove with a small hand held rasp to make a small chamfer would de-burr the groove.
 
The soft brg material is ultra thin & the steel backing which is cut into is thick & will be raised. Photo copy paper is about 0.004" thick. How do you tell that the 'de-burr' didn't leave raised metal that only has to be 0.001" high to cut into the crank. By eye? By feel? Good luck with that. Wouldn't trust either method to pick up 0.001".
 
Bewy said:
The soft brg material is ultra thin & the steel backing which is cut into is thick & will be raised. Photo copy paper is about 0.004" thick. How do you tell that the 'de-burr' didn't leave raised metal that only has to be 0.001" high to cut into the crank. By eye? By feel? Good luck with that. Wouldn't trust either method to pick up 0.001".
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Crank journals are hardened. The steel backing on main bearings is not, that is so the bearing shell will conform to the crank main bores in the block.
To inspect, add a chamfer. With a chamfer present, there can not be a burr.
 
my68barracuda said:
Crank journals are hardened. The steel backing on main bearings is not, that is so the bearing shell will conform to the crank main bores in the block.
To inspect, add a chamfer. With a chamfer present, there can not be a burr.
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Good discussion guys thanks for the info
 
Bob,
Some BS creeping in here. There is no mention of your crank material, but since you are talking about increased oiling, I assume it is a performance engine & using a forged steel crank. These can be Tufftrided or Nitrided, both extremely thin chemical treatments that are gone if the crank is ground undersize; some have neither treatment & are just plain ole steel...Same with cast iron crank, plain ole CI.
The steel brg shell is as hard as the f/steel or CI. It is a 'springy', hard, steel, because when you insert it, & then remove it, it springs back into shape; mild steel does not do that.
Unless you have some method of accurately checking for raised metal, as I described earlier in this thread, you would be better of not attempting this mod at home.
 
So, I think if you have a raised edge from the cut, it may have the propensity to squish both in and outside of the groove. This could be a problem when the mains are torqued. The babbit can accumulate and get dragged around by where the oil hole is. I had an LS motor in a yukon that was seized, when I took it apart, there had to have been a 1/8 groove in the bearing, and a chunk that had grown considerably, ultimately stopping the crank from rotating. I still have the bearing, can probably find a picture. But anyway, to mitigate this problem, you can always make a bearing scraper out of an old file. Grind down and sharpen the 3 sides of the file about an inch, and scrape the burrs. I usually use this on new cam installs. Put it in, turn it, see where it’s tight(marks on bearing) and scrape each part until it moves freely. You could probably use a knife. I was advised to not try and use scotch bright pads on bearing material to remove burrs
 
Bewy said:
Bob,
Some BS creeping in here. There is no mention of your crank material, but since you are talking about increased oiling, I assume it is a performance engine & using a forged steel crank. These can be Tufftrided or Nitrided, both extremely thin chemical treatments that are gone if the crank is ground undersize; some have neither treatment & are just plain ole steel...Same with cast iron crank, plain ole CI.
The steel brg shell is as hard as the f/steel or CI. It is a 'springy', hard, steel, because when you insert it, & then remove it, it springs back into shape; mild steel does not do that.
Unless you have some method of accurately checking for raised metal, as I described earlier in this thread, you would be better of not attempting this mod at home.
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The crank journals wether a steel crank or a cast crank are induction hardened.
An outline of the process is:
1) crank journals and mains are cut to size + a few thousands using normal cutting tools
2) the pins and mains are induction hardened, basically a heat and quench.
3) the pins and mains are then ground to size.
The reason they are ground is they are too hard to be cut with normal cutting tools.
The backing steel on plain bearings is dead soft. The backing steel is soft so it conforms to the round shape of the block bearing bridge-main cap or the big end of the rod.
If one wants to verify this, take a sharp hand file, place it on a edge and using hand pressure run the file across a crank main or rod journal. The file will zing across the surface because the surface is hard.
Using the same file and the same pressure, run the file across the steel backing of a plain bearing half round. The file will cut into the steel backing because the surface is soft steel.
Note: on crankshafts, only the machined surfaces and nearby radius of the pins and mains are induction hardened, the counter weights and machined flanges are not hardened.
it is true that nitride and tuftride treatments are thin, but those treatments are typically used on HD crank applications and not automotive applications, even automotive preformance cranks don’t always get those treatments.
Ask your local crankshaft shop if they send all crankshafts out for nitriding or tuftriding after the journals and mains are cut undersized. The answer will be only if the customer pays for it.
That is because the tuftride - nitride adds additional hardness to the very top of the already hard induction hardened zone. The induction hardened zone goes into the crank .060 to .080 thousands, that is why one can have .010, .020 ground from a crank main or pin and not have to re harden the main or journal.
 
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My 68,
Don't know how many times you have to hear it but slipper brg shells are NOT dead soft. They are made of a springy type of hard steel. Squeeze a shell & it release, it springs back out. Squeezing the same thickness of mild or soft steel & it will bend.
The reason cranks are ground is not because they are 'too hard' for cutting tools. They are ground [ like cam lobes are ] because the smooth fine finish reqd can only be achieved by grinding, then linishing.
A file will also scratch/leave a mark on a crank journal.
 
Leaving a mark or a scratch is not the same as producing filings and removing metal.
I am not surprised that you do not know that cam lobes are hardened. Or that you are unaware that the toughness-hardness of the material being cut determines the metal shaping process. There are several turning, milling and burnishing methods that could be used to get a smooth cam lobe shape on soft metal, but cam lobes are ground because they are hardened.

I see no reason to continue to banter with you. One does not need know how things are made to be an automotive enthusiast, but it does limit your ability to participate in a discussion.
 
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68,
Where did I mention that cam lobes are not hardened? In fact I referenced the hardness of cam lobes in post #19.
 
I really appreciate all the good information. I have a brand-new Molnar crank I’m not sure what they use as far as heat treating. I’m upgrading the oiling system some with a larger suction tube. I’ve massaged around the oil pump inlet and main cap I’ll probably leave the bearings alone. RPM over 6000 will be rare 6500 max. I’ve got a modified pan with sump and baffles. Engine is stroked 340, 395 CID
 
A fingernail can catch a burr as small as .0003 in my experience.
Improper cutting can displace material in a way that's not a burr, but is still a problem. Plastigage would reveal this kind of issue.
So, Plastigage and fingernail test. Done..
 
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