crankpin diameters

[lucasracing]

We are redesigning an early French race engine . We plan to use a two piece split cage needle bearing on the big end of the connecting rod . This appears to be a style of bearing used on outboard engines . My question is what engine that uses a split needle connecting rod bearing has the largest crankpin diameter ? Or in other words what outboard has the largest two piece style connecting rod bearings ? I would greatly appreciate any help you could give me . Greg

 

[snapperbait]

Re: crankpin diameters

Sounds interesting Greg...<br /><br />Here's a few examples...<br /><br />OMC/Johnson/Evinrude.. Split cage needle bearings on 1985-thru V4 120-140hp, and V6 200-225 hp 1986-thru uses a 1.4995"-1.5000" crankpin diameter..<br /><br />Mercury... All v6 engines thru 1989 have 1.499" crankpin diameters..<br /><br />These are about the biggest outboards crankpin diameters you'll find with the possible exceptions of Mercury's 3.4 litre 300hp V6 and Johnson/Evinrude V8 300hp, for which I do not know the specs for either...

 

[rodbolt]

Re: crankpin diameters

Hello<br /> you may also look at the centermain bearings on various merc,OMC or yamaha cranks, most of them are split main with outer races, the early small crank 25-35 used a stailess steel liner for a bearing race

 

[Silvertip]

Re: crankpin diameters

If this engine originally used an insert style of bearing and you plan to run a split cage needle bearing you will need to rethink the oiling system. Oil feeds to the journals closest to the pump will likely free-flow and the farthest journals will starve. Insert bearnings have approximately .001 - .003 inch oil clearance while a needle bearing would be wide open in comparison so you would experience a pressure problem. Porsche used a roller bearing crank in what I remember as an "RSK". Perhaps a little research into that engine would be of help. If this works, the engine will definitely pick up some HP.