Full Groove Mains are out?

Full Groove Mains are out?

Joined: December 16th, 2003, 1:59 am

January 18th, 2012, 7:46 pm #1

recently i've seen a couple comments regarding full groove mains being 'old tech' or just not stylish lately... i did a quick search but didn't find the referenced MME Mark comments, possibly on another forum?

i just don't get why shutting off the oil flow to the rod bearings 50% of the time can be considered a Good Idea ?

when i picture the scene 4th dimensionally i'm seeing the oil columns in the crank drillings Pulsing rather than flowing smooth & constant. any time you interupt something it takes time & energy to re-establish, so the ON time of the oil column may be significantly less than 50% ?

the original Recipe for the Cleveland included full groove main bearings, at least on the higher output rated versions. possible the 2V's maybe even the base 4V's came with 1/2 grooves?

but it don't make no sense to me, rod bearings need oil man





there'll be phantoms, there'll be fires on the road... and the white man dancing
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Joined: October 1st, 2004, 8:05 pm

January 18th, 2012, 9:31 pm #2

The text below is from a tech bulletin by Mahle/Clevite

What they are saying is that a half groove main bearing (only the upper shell is grooved) is better
for the life of the lower main bearing shell. Duh. What they don't mention whatsoever is how this
impacts the life of the connecting rod bearings.

______________________________________________________________________

Influence of Grooving on Main Bearing Performance

Various forms of main bearing grooving have been used over the years. We are frequently
asked what difference grooving makes.

First, its essential to understand that bearings depend on a film of oil to keep them separated
from the shaft surface. This oil film is developed by shaft rotation. As the shaft rotates it pulls
oil into the loaded area of the bearing and rides up on this film much like a tire hydroplaning on
wet pavement. Grooving in a bearing acts like tread in a tire to break up the oil film. While you
want your tires to grip the road, you dont want your bearings to grip the shaft, so grooving is
bad for maintaining an oil film. The primary reason for having any grooving in a main bearing is to
provide oil to the connecting rods. Without rod bearings to feed, a simple oil hole would be
sufficient to lubricate a main bearing.

Many early engines used full grooved bearings and some even used multiple grooves. Those
choices were based on what engineers knew at the time. As engine and bearing technology
developed, the negative effect of grooving was recognized and bearing grooving was removed
from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on.
This provides a greater safety margin and improved bearing life. Upper main shells, which see
lower loads than the lowers, and hence dont apply the same load to the oil film, have retained a
groove to supply the connecting rods with oil.

In an effort to develop the best possible main bearing designs for High Performance engines,
weve investigated the effects of main bearing grooving on bearing performance. The graphs on
the next page illustrate that a simple 180° groove in the upper main shell is still the best overall
design.

While a slightly shorter groove of 140° provides a marginal gain, most of the benefit is to the
upper shell, which doesnt need improvement. On the other hand, extending the groove into the
lower half, even as little as 20° at each parting line (220° in total), takes away from upper
bearing performance without providing any benefit to the lower half. Its also interesting to note
that as groove length increases so do Horsepower Loss and Peak Oil Film Pressure which is
transmitted directly to the bearing.

Bearing Grooving Tech Bulletin



-G
____________________________________________________________

Pantera Photos | 351C Historic Information | 351C Technical Information

If you use a 351C 4V powered vehicle for a grocery getter ... the eggs aren't going to make it home!
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Joined: September 30th, 2009, 7:08 pm

January 18th, 2012, 10:19 pm #3

So does the part of the lower bearing opposite the groove wear faster than the rest of the bearing? I'm assuming if the wear was enough to impact bearing life, they'd have to groove the entire bearing, but it never hurts to ask....
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Joined: January 10th, 2002, 5:53 pm

January 19th, 2012, 2:28 am #4

recently i've seen a couple comments regarding full groove mains being 'old tech' or just not stylish lately... i did a quick search but didn't find the referenced MME Mark comments, possibly on another forum?

i just don't get why shutting off the oil flow to the rod bearings 50% of the time can be considered a Good Idea ?

when i picture the scene 4th dimensionally i'm seeing the oil columns in the crank drillings Pulsing rather than flowing smooth & constant. any time you interupt something it takes time & energy to re-establish, so the ON time of the oil column may be significantly less than 50% ?

the original Recipe for the Cleveland included full groove main bearings, at least on the higher output rated versions. possible the 2V's maybe even the base 4V's came with 1/2 grooves?

but it don't make no sense to me, rod bearings need oil man





there'll be phantoms, there'll be fires on the road... and the white man dancing
He used to work for FM. A wideer bearing has more suport for the oil film that sulds up the crank. I've not seen any issues with the half groove bearings during street or racing use.

1967 Falcon 4 door 351C-4V
1970 Mustang 351C-2V
http://raceabilene.com/kelly/hotrod
Owner built, owner abused.
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Joined: July 12th, 2008, 1:55 pm

January 19th, 2012, 10:18 am #5

The text below is from a tech bulletin by Mahle/Clevite

What they are saying is that a half groove main bearing (only the upper shell is grooved) is better
for the life of the lower main bearing shell. Duh. What they don't mention whatsoever is how this
impacts the life of the connecting rod bearings.

______________________________________________________________________

Influence of Grooving on Main Bearing Performance

Various forms of main bearing grooving have been used over the years. We are frequently
asked what difference grooving makes.

First, its essential to understand that bearings depend on a film of oil to keep them separated
from the shaft surface. This oil film is developed by shaft rotation. As the shaft rotates it pulls
oil into the loaded area of the bearing and rides up on this film much like a tire hydroplaning on
wet pavement. Grooving in a bearing acts like tread in a tire to break up the oil film. While you
want your tires to grip the road, you dont want your bearings to grip the shaft, so grooving is
bad for maintaining an oil film. The primary reason for having any grooving in a main bearing is to
provide oil to the connecting rods. Without rod bearings to feed, a simple oil hole would be
sufficient to lubricate a main bearing.

Many early engines used full grooved bearings and some even used multiple grooves. Those
choices were based on what engineers knew at the time. As engine and bearing technology
developed, the negative effect of grooving was recognized and bearing grooving was removed
from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on.
This provides a greater safety margin and improved bearing life. Upper main shells, which see
lower loads than the lowers, and hence dont apply the same load to the oil film, have retained a
groove to supply the connecting rods with oil.

In an effort to develop the best possible main bearing designs for High Performance engines,
weve investigated the effects of main bearing grooving on bearing performance. The graphs on
the next page illustrate that a simple 180° groove in the upper main shell is still the best overall
design.

While a slightly shorter groove of 140° provides a marginal gain, most of the benefit is to the
upper shell, which doesnt need improvement. On the other hand, extending the groove into the
lower half, even as little as 20° at each parting line (220° in total), takes away from upper
bearing performance without providing any benefit to the lower half. Its also interesting to note
that as groove length increases so do Horsepower Loss and Peak Oil Film Pressure which is
transmitted directly to the bearing.

Bearing Grooving Tech Bulletin



-G
____________________________________________________________

Pantera Photos | 351C Historic Information | 351C Technical Information

If you use a 351C 4V powered vehicle for a grocery getter ... the eggs aren't going to make it home!
Somebody better tell King! Their high performance Allecular main bearings are grooved well down into the lower shell. Hmmm.
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Joined: February 19th, 2005, 5:39 pm

January 23rd, 2012, 2:29 am #6

He used to work for FM. A wideer bearing has more suport for the oil film that sulds up the crank. I've not seen any issues with the half groove bearings during street or racing use.

1967 Falcon 4 door 351C-4V
1970 Mustang 351C-2V
http://raceabilene.com/kelly/hotrod
Owner built, owner abused.
I think this is the thread you're looking for about fully grooved bearings. I use 3/4 groove myself.
Mike
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Joined: December 5th, 2004, 11:36 pm

January 23rd, 2012, 2:56 am #7

Hey, just pulling down my 2V drag engine for a freshen.......its done 2 full seasons in an 11.0 sec combo. Its old school and low budget, stock rods, stock crank, heavy pistons. I run two upper shells to create a fully grooved main in every engine that sees north of 7000 rpm. Stock volume pump and 3 + thou clearance on both mains and rods.

Photos are of the lower halves of this engine, wear for 2 seasons looks great. Big ends are the same condition.

[/IMG]


[/IMG]


The limiter in this is set at 7600 and its been there plenty of times.

Runs a home made sump and windage tray, one thing I've noticed is some "cleaner" patches on the underside of the intake that line up with the oil drain backs (enlarged) in the valley. They suggest to me a lot of windage and no doubt some hp loss as a result.

This time around its getting lifter bushings and I think plain halves in the bottom........will be an interesting excercise but might have to wait a year or 2 for results!

I'm breaking the old rule of "if it aint broke dont fix it" and running a full groove main has worked very well for me in the past. Will be interesting to see if it shows any improvement at the track.
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Joined: April 18th, 2008, 5:09 pm

January 23rd, 2012, 6:27 am #8

The text below is from a tech bulletin by Mahle/Clevite

What they are saying is that a half groove main bearing (only the upper shell is grooved) is better
for the life of the lower main bearing shell. Duh. What they don't mention whatsoever is how this
impacts the life of the connecting rod bearings.

______________________________________________________________________

Influence of Grooving on Main Bearing Performance

Various forms of main bearing grooving have been used over the years. We are frequently
asked what difference grooving makes.

First, its essential to understand that bearings depend on a film of oil to keep them separated
from the shaft surface. This oil film is developed by shaft rotation. As the shaft rotates it pulls
oil into the loaded area of the bearing and rides up on this film much like a tire hydroplaning on
wet pavement. Grooving in a bearing acts like tread in a tire to break up the oil film. While you
want your tires to grip the road, you dont want your bearings to grip the shaft, so grooving is
bad for maintaining an oil film. The primary reason for having any grooving in a main bearing is to
provide oil to the connecting rods. Without rod bearings to feed, a simple oil hole would be
sufficient to lubricate a main bearing.

Many early engines used full grooved bearings and some even used multiple grooves. Those
choices were based on what engineers knew at the time. As engine and bearing technology
developed, the negative effect of grooving was recognized and bearing grooving was removed
from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on.
This provides a greater safety margin and improved bearing life. Upper main shells, which see
lower loads than the lowers, and hence dont apply the same load to the oil film, have retained a
groove to supply the connecting rods with oil.

In an effort to develop the best possible main bearing designs for High Performance engines,
weve investigated the effects of main bearing grooving on bearing performance. The graphs on
the next page illustrate that a simple 180° groove in the upper main shell is still the best overall
design.

While a slightly shorter groove of 140° provides a marginal gain, most of the benefit is to the
upper shell, which doesnt need improvement. On the other hand, extending the groove into the
lower half, even as little as 20° at each parting line (220° in total), takes away from upper
bearing performance without providing any benefit to the lower half. Its also interesting to note
that as groove length increases so do Horsepower Loss and Peak Oil Film Pressure which is
transmitted directly to the bearing.

Bearing Grooving Tech Bulletin



-G
____________________________________________________________

Pantera Photos | 351C Historic Information | 351C Technical Information

If you use a 351C 4V powered vehicle for a grocery getter ... the eggs aren't going to make it home!
Suggest when you spec' grooved main bearings other than stock, you also tell your bearing suppliers whether you are running Ford-width con rods or SBCs as are commonly supplied with Ford stroker cranks. Real-racers found eons ago that the diameters and widths of the SBC rod bearing had better reliability at high rpm than Fords, even though both rod bearings are within a few percent in terms of surface area. The smaller dia, but wider Chev rod bearings lived longer under 'heavy duty use' than the larger diameter but narrower Ford rod bearings; something about oil spreading and load carrying. Presumably this would be another thing to consider in choosing which main bearing groove length you'd use in a high effort, high dollar engine.
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Joined: February 19th, 2005, 5:39 pm

January 23rd, 2012, 6:22 pm #9

Hey, just pulling down my 2V drag engine for a freshen.......its done 2 full seasons in an 11.0 sec combo. Its old school and low budget, stock rods, stock crank, heavy pistons. I run two upper shells to create a fully grooved main in every engine that sees north of 7000 rpm. Stock volume pump and 3 + thou clearance on both mains and rods.

Photos are of the lower halves of this engine, wear for 2 seasons looks great. Big ends are the same condition.

[/IMG]


[/IMG]


The limiter in this is set at 7600 and its been there plenty of times.

Runs a home made sump and windage tray, one thing I've noticed is some "cleaner" patches on the underside of the intake that line up with the oil drain backs (enlarged) in the valley. They suggest to me a lot of windage and no doubt some hp loss as a result.

This time around its getting lifter bushings and I think plain halves in the bottom........will be an interesting excercise but might have to wait a year or 2 for results!

I'm breaking the old rule of "if it aint broke dont fix it" and running a full groove main has worked very well for me in the past. Will be interesting to see if it shows any improvement at the track.
I would not go over .003" IMO. I like 3/4 groove with .0025" - .003".
Mike
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