Wide VS narrow rod bearings

[Mike T]

Let me start by apologizing to Brian (bison) for stealing this photo from one of his recent threads.... I didn't want to start a new discussion within his thread.

In the photo you can see how the narrow bearing rides on the journal leaving only a little extra room close to the fillets. When using the wide version bearing this area would most likely be covered creating a somewhat larger surface area and in theory this would be a good thing.

I know a lot of guys prefer wide bearings but I've always considered the possibility of the wide bearing hanging past the surface area of the journal when used on a stock rolled fillet crank. The little extra surface area sounds good but it seems like the bearing may tend to "dish " for a lack of a better term.

Any options on this?

 

[markrussell0927]

Everyone that I know uses the wider bearings in their rebuilds. My opinion on the matter is there is a lot of stock engines with over 100,000 miles and still being driven hard. The stock rod bearings are gonna do the trick just fine, but after holding both sets in my hand I elected to go with the wider ones. They aren't much wider just enough to help displace the stress put on the rods because of our engines design.

 

[Mike T]

I don't have a wide bearing in front of me to measure but if the bearing filled the entire rod saddle to the chamfer it would seem like the bearing would overhang the fillet?

 

[markrussell0927]

I'm almost positive they won't overhang the fillet. I will have my engine in front of me sometime next week for assembly I can post pics and help u further if someone else doesn't chime in. I believe the factory rod bearing doesn't fit the journal all the way that's why the wider ones are desired. I think the wider bearing fits the journal perfectly. If you zoom in on the pic you posted you can see the bearing to journal clearance on the upper portion and it does look smaller than the journal

 

[Mike T]

That would be great if you could post your findings. There may be no downside even if the do hang over but this is something that I've been curios about.

 

[markrussell0927]

This is an old pic from super chevy that compares the two side by side

 

[WPP-Bill]

The rolled radius will vary from one journal to the next, but the bearing surface is approximately .675-.700 wide on the stock cranks I've looked at. A wide journal bearing comes in at .735 wide, leaving an overhang of .035 - .060. Hope that gives you some numbers to work with Mike.

 

[Mike T]

The rolled radius will vary from one journal to the next, but the bearing surface is approximately .675-.700 wide on the stock cranks I've looked at. A wide journal bearing comes in at .735 wide, leaving an overhang of .035 - .060. Hope that gives you some numbers to work with Mike.

Yes this is very good info....this confirms what I suspected. Thank you.

 

[markrussell0927]

Got my engine back today and will post pics of the 2 rod bearings on the crank.