Cam bearing position

[George vega]

I read an article where they were installing cam bearings at a 4 Oclock position instead of lining up the holes. Is that correct or is it certain types of bearings only?

[blykins]

It's for any cam bearing that has a groove behind it. 

You can go the 4:00 route, or you can install them the traditional way, with the hole lining up with the hole in the main saddle.  Millions of FE's out there with the holes lined up.

[scott foxwell]

[Ranch]

AERA/AERSCO
AERA Technical Services Departmart
500 Coventry Lane, Suite 180 Crystal Lake IL 60014
Phone 888/324-2372 Fax 888/329-2372
TECHNICAL BULLETIN
July 2002
TB 1996
Optimum Placement of Camshaft Bearing
Oil Feed Hole Location
The AERA Technical Committee offers the following important information on optimum placement of camshaft bearing oil feed hole location during installation.
This information should be considered any time camshaft bearing replacement is being done.
Maximum camshaft support will be realized by installing the cam bearing oil feed hole to the optimum clock location. Blocks and heads using a 360° oil groove located behind the bearing oil feed, allow one to move the clock position of the cam bearing oil feed hole. This way you can adjust the clock position during cam bearing installation to make sure that the optimum location for the best hydrodynamic wedge is selected. Locating and installing the cam bearing to take advantage of this hydrodynamic wedge will supply the maximum support for the camshaft during engine operation. The direction of camshaft rotation and the engine oil entry point into the bearing control the placement of the hydrodynamic wedge.
Note: If the oil feed passage in the block or head is just a hole without a 360° groove, the bearing oil hole must line up with the oil feed passage in the block or head. In some instances, the bearing oil feed hole in the cam bearing also lines up with a groove cut in the camshaft journal. In those instances, the location of the bearing oil feed hole in the bearing is also very critical fore and aft and may not match up 100% with the hole in the block or head.
The illustration in Figure 1 below shows the optimum engine oil feed hole location for a camshaft that is turning clockwise as viewed from the front of the engine.
Note: If the camshaft being used is driven with a gear-to-gear arrangement, or is a reverse rotation engine with a chain drive, the cam bearing oil feed hole will require repositioning to the opposite lower side. This is due to the fact that the camshaft is turning in the opposite direction as noted above.
The AERA Technical Committee

Sorry can't seem to post the diagram but it shows most any place cept 5 thru to 9 o'clock position being the worst and about 12to3 being the better.   Hope that helps

I see Scott was able to post my old diagram "picture" worth a thousand words,  Good job Scott

[jayb]

It was always interesting to me that the factory lined the holes up, at least on the undisturbed engines I've taken apart.  I built them that way for many years and never had an issue, but always milder engines.  I had a guy call me recently who experienced cam bearing failure on a fairly strong roller cam engine, a 428 if I recall correctly.  His bearings were installed at 4:00, which should have been fine, but his bearings were all worn at the bottom, like not enough oil was present.  I suspect he had a cam journal alignment issue, but hard to say for sure.

I was consulting with Bill Conley on the design of my bushed SOHC rockers and Bill had me put the oiling hole for the bushing at the 12:00 position.  Based on the diagram above, that's the right spot...

[scott foxwell]

It was always interesting to me that the factory lined the holes up, at least on the undisturbed engines I've taken apart.  I built them that way for many years and never had an issue, but always milder engines.  I had a guy call me recently who experienced cam bearing failure on a fairly strong roller cam engine, a 428 if I recall correctly.  His bearings were installed at 4:00, which should have been fine, but his bearings were all worn at the bottom, like not enough oil was present.  I suspect he had a cam journal alignment issue, but hard to say for sure.

I was consulting with Bill Conley on the design of my bushed SOHC rockers and Bill had me put the oiling hole for the bushing at the 12:00 position.  Based on the diagram above, that's the right spot...

A lot of things can cause that but most cam bearing wear is from dry start up. One reason I like to use coated cam bearings when they're available. I don't doubt that low idle oil pressure and heavy springs are also a factor.
One nice thing about the FE cam journal is the groove. You can also drill an extra hole in the bearing which doesn't hurt. One at 12:00 and one at 4:00.

[Barry_R]

About 99% of aftermarket and OE cam bearings are made from some variation of Babbitt, which by nature is a fairly low load bearing material as far as bearings go.  But very forgiving.  At F-M we had some special high load materials used in NASCAR specials and in the 1268M, but I suspect those alloys disappeared when F-M abandoned cam bearing manufacturing and went to Duarabond as a supplier.

Pretty much every side oiler has to have the oil feed holes aligned with the bottom in order to feed the heads - and those engines are most likely to have the highest load cam packages. 

Full round bearings such as cam bearings do not develop the same hydrodynamic wedge as does a bearing with eccentricity, and darn near nobody ever seems to check cam bearing clearances.

All these things coupled together means that I am often amazed that we do not see more cam bearing failure than we do.  They must fall under the category of "good enough is good enough" for most builds.

Working with currently available alloys, I think Robert Pond had the right idea in making the cam bearing wider - if only the journal on the cam was wider too in order to spread out the load.

[scott foxwell]

Where there is no groove in the journal, it's very easy to groove the back of a cam bearing.

[blykins]

Again, I just think it's one of those things that aren't necessary.  Every aftermarket FE block out there uses a typical S/O cam bearing layout.  They will take some *extreme* valve spring pressure without hurting the bearings, with the main feed hole being in line with the hole in the main saddle. 

[scott foxwell]

Again, I just think it's one of those things that aren't necessary.  Every aftermarket FE block out there uses a typical S/O cam bearing layout.  They will take some *extreme* valve spring pressure without hurting the bearings, with the main feed hole being in line with the hole in the main saddle.

If I didn't do everything that "wasn't necessary", I'd be out of a job.

[blykins]

Gotta know where to draw the line.  Otherwise you'll end up with a 450 hp engine with an aftermarket block, billet crank, custom Callies rods, dry sump, .937" lifters....................................

After a while you learn what makes a difference and what doesn't.  Most of the "oil mods" are from the 60's where the mindsight was, "If small is good, big is gooder...."  That's how we ended up with Tunnel Port intake port dimensions, Cleveland 4V intake port dimensions, and all the block holes drilled out until the block cracked.

[George vega]

Thanks for the info. Alot of good information here.

[My427stang]

I am with Brent here.  I'll add though, I'd love to see a better representation of the load axis, because it's likely  1) a continuously moving range, not an arrow.  and 2) a function of lifter bore angle AND lobe shape.  My hunch is portions of the opening ramp have more violent pressure than the direction of the pushrod.   So, not a fixed location for every engine

Of course you could use average load axis by finding the center, but then you really are only being precise in installation, probably not function   I am not an engineer, but seems to me on any engine with opposed banks, that picture of the "best place" would have the load and optimum oil hole in the very least rocking back and forth like a metronome and probably not clocked to true north.