Widest Rod Bearing For Stock Crank?

[9SECVSIX]

Federal 3755APA and Federal 3760A have been discontinued, what's available in .721" width these days?

 

[buickGN3:16]

hopefully earl will jump in but i think he said get bearrings for a 3.8 buick lesabre when i was asking this question. They are wider


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[earlbrown]

'95 Buick Park Ave with a 3800.

Those bearings haven't been discontinued they just had a part number change. (and I can NEVER remember the new part number)

 

[TexasT]

What is the advantage of a wider bearing? Seems it would have more drag, but I guess it gives more surface area to distribute force on the crank.

TIA
Rich

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[buickGN3:16]

sorry earl, i was close !


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[earlbrown]

The wider bearing is so much wider as it is the correct size. If you open up a virgin engine the stock bearing doesn't even cover the width of the rod or the journal.

Yes, there probably is a slight amount of vicious friction added due to holding more oil in the hydrodynamic wedge.... but putting in skinnier bearings isn't the best way to free up horsepower. Plus you can offset the marginal addition of drag with thinner oil to maintain the same pressure.

When loading something so small with so many thousands of pounds of pressure I'll take the 12%~15% more load area any day of the week.

 

[TexasT]

Cool, thanks good to know.
Are the rockauto clevite .721 good and if so which ones as there are two choices. If not are the ones above necessary or are other brands just as good?

http://www.rockauto.com/catalog/moreinfo.php?pk=2990280&cc=1019832

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[earlbrown]

They look like they copied the Federal Mogul A-series the OP asked about.

Personally I'll never put my hands on any clevite bearings again and I'm very happy with my FM A-series.

 

[David Husek]

The bearing numbers are 6760A for sealed power, CB1443P or A for clevite, CR6664AM for king, 6B1443P or A for ACL. The acl P will be an extremely hard to find. If using a steel crankshaft, use sealed power 6-7120CH.

 

[9SECVSIX]

The bearing numbers are 6760A for sealed power, CB1443P or A for clevite, CR6664AM for king, 6B1443P or A for ACL. The acl P will be an extremely hard to find. If using a steel crankshaft, use sealed power 6-7120CH.

Thanks! David. Do you know if the CB 1443P comes in a .001" undersize?

 

[3rdgeniroc]

Clevite 1398H is another option for the stock crank. Comes in standard, .001 and .010

 

[9SECVSIX]

Clevite 1398H is another option for the stock crank. Comes in standard, .001 and .010

that's what I always use on steel cranks but I thought they were to hard for the soft cast crank, JMO. Isn't that a wide journal bearing also?

 

[SS/GN]

( If using a steel crankshaft, use sealed power 6-7120CH.) Dave this # looks to be a standard width 87 3.8 design. I also noticed that Webers recommends the stock 87 width bearing with all cranks. I guess my question is does the wider bearing really offer a benefit. Thanks for the input.

 

[earlbrown]

Of course it offers a benefit. During ignition the rod pushes against the crankshaft and the only thing that keeps the two from hitting is oil.

Lets say there's 100PSI between the two (nice even number) and you increase your loaded bearing area 15%.... the result is a proportional increase in protection. PSI is 'pounds per square inch'. Any time you increase your square inches, you can either tolerate more load safely, handle the same load with less oil pressure... or a combination of the two.

The other benefit is moving the edges of the load closer to the sides of the journal. That will remove some of the rods tendency to try and bend the crank in the middle of the journal. Image our crank journals are 10 feet wide and the rod is 1/2" pushing right in the middle. It will take X amount of force to bend it.

Now image the 10 foot crank journal has a 9.75' wide rod/bearing pushing down on it. It will much much harder to bend that same journal.

 

[David Husek]

Thanks! David. Do you know if the CB 1443P comes in a .001" undersize?

Yes they are available in .001 size.

 

[David Husek]

( If using a steel crankshaft, use sealed power 6-7120CH.) Dave this # looks to be a standard width 87 3.8 design. I also noticed that Webers recommends the stock 87 width bearing with all cranks. I guess my question is does the wider bearing really offer a benefit. Thanks for the input.

The stock rod bearings width work well, they have been used for years with no problems and many builders use the stock width rod bearing.

Increasing bearing surface is always good insurance. Our motors are off-center, which means the rods are not in the center of the cylinder bore, they are offset. So there is always a side load on the rod bearing. This is noted when tearing down stock motors; the rod bearings will show uneven wear. The wider bearing will help with this load. Most of the stage motors built run wide journal cranks which are .040 wider than stock rod journals. The bearings used for the wide journal rods are cb1398H.

By adding bushed rods so the wristpin is full floating helps with the side load and it increases bearing surface. I usually don’t see much uneven wear with bushed rods.

 

[Tim Cucci]

Of course it offers a benefit. During ignition the rod pushes against the crankshaft and the only thing that keeps the two from hitting is oil.

Lets say there's 100PSI between the two (nice even number) and you increase your loaded bearing area 15%.... the result is a proportional increase in protection. PSI is 'pounds per square inch'. Any time you increase your square inches, you can either tolerate more load safely, handle the same load with less oil pressure... or a combination of the two.

The other benefit is moving the edges of the load closer to the sides of the journal. That will remove some of the rods tendency to try and bend the crank in the middle of the journal. Image our crank journals are 10 feet wide and the rod is 1/2" pushing right in the middle. It will take X amount of force to bend it.

Now image the 10 foot crank journal has a 9.75' wide rod/bearing pushing down on it. It will much much harder to bend that same journal.

Perfect Example!
So does using the wider bearings require chamfer on stock rods and stock standard crankshafts? And if so why?

 

[earlbrown]

They do not. 100% drop in with stock cranks and rods.


I re-read what I posted and thought I was drunk when I wrote it as I had no recollection of doing it.

...then I noticed it was from 2013. lol

 

[Tim Cucci]

Sorry to go so far back but I am getting prepped and and doing research. Ordrering parts for my spare block soon to be put together from an assortment of gathered parts. Stock crank and rods with .020 JE pistons. Getting it all together for mockup and balance. I need bearings and rings. I really appreciate the knowledge and expertise here.

 

[Reggie West]

You can get the Clevite bearings from Summit still.