[68WarDog]

While at the boat shop having my engine tore down for a rebuild.One of the marine mechanics was showing me the roller bearings used on the rods.I began to think what a great idea for our vintage Pontiacs or has this been tried before?Seems to me that, minus the cost,this would free up added hp and increase engine longevity.

[mysticmissle]

i think what you are missing is the fact that a roller bearing does not come in halves, like a shell type rod bearing, they are used in full circle applications such as cam bearings, or on shafts

[Tom Vaught]

In some areas of the engine like the cam shaft journals roller bearing parts are actually available for our Pontiacs.

As was mentioned, it would be very difficult to add them to a one piece crank like a pontiac has.

Tom V.

[b-man]

When I was into building up and racing air-cooled 4-cylinder VW engines roller bearing crankshafts were available from a company called SPG, and they were very expensive precision pieces.

Since the rods were one-piece deals the multi-piece crankshafts were pressed together at the rod journals in order to assemble the rods and roller bearings to the crank. Not the kind of crank you could ever consider doing work on yourself, if there were any problems you had to send it to SPG for repair.

Due to the roller bearings inability to take high shock loads, compression ratios on engines using the SPG cranks were limited to 9:1 and RPM was also limited to around 7500. The rod bearings were splash-lubed (open slots for oiling), no oil pressure to the rods. Main bearings were regular insert bearings.

Drag-race starts were frowned upon, the cranks would slip at the press-fit joints when the shock of a clutch-dumping launch hit. Since I was into drag racing I didn't even consider using a roller-bearing crankshaft, couldn't afford one if I wanted one anyway.

Good crank design for road-racing, in the '50s and early '60s Porsche Carrera 4-cylinders used a Hirth (aircraft engine maker) roller-bearing crank. These 1.5 (150 HP) to 2-liter (200 HP) 4-cam, twin-ignition engines were used in the legendary mid-engine 550 Spyder (James Dean died in one) and were very successful. One good thing about the roller crank was if you ever lost oil pressure during a race you could run it a bit longer than a plain-bearing engine and perhaps make it back to the pits for repairs, big plus.

[Skip Fix]

I remember seeing ads for those VW roller cranks.We stuck a valve in my wife's old VW going down the freeway, luckily I was driving and knew to push in the clutch when it locked up.

Since you mentioned air craft engines how do the piston engines keep oil around the pickup when upside down? Saw a picture of a experimental plane using an new LS1 but couldn't see the oil system, looked like a dry sump tank in the picture.

[Jurassicgto]

Being upside down is not the limit. Negative g's are the limit usually measured in seconds. You can be rightside up and get negative g's by pushing forward on the stick with a lot of force. Kind of like going over the apex of a hill fast in your car and your stomach feels like it's coming up. Oil systems are limited from that type of movement. You can fly upside down and keep positive g's on an airplane and everything is happy,no time limit, until you run out of altitude. Aircraft and pilots cant tolerate negative g's very well.

[68WarDog]

Lot of good information guys.Tom I will lookup one of the vendors regarding the cam journal roller bearings.It would seem that any reduced friction surfaces(roller rockers,cam journal/lifters) would free up hp and wear potential.

["Me"]

Most two strokes are made this way.

Larry

[mechanickeith]

Saab Sonnet's, early 60's also had roller bearings, multi piece cranks, had to be pressed together, ( 2 stroke engines). I have seen roller bearings in cages that came in 2 halves. Cant remember what the application was.