The Official 356Talk Forum

is that oil or all vic?

Roller bearing cranks were discontinued by Porsche during the late 1950s, however, new roller bearing cranks were still being sold through the early 1970s. I have older magazines showing them for sale at the price of $155.00, with rods and main bearings. ( Valley Core Co.). It is therefore likely that a number of these were fitted during rebuilds in the 1970s and can explain why an owner has a 'roller' in his/her car.

Were those factory Hirth or the SPG one?

Not sure...the ad isn't specific as to the manufacturer. It did say that the cranks featured micro-jet lubricated main bearings but no other details. Valley Core had eight different advertisements in the June '69 issue of Panorama, including the full back cover....Quite a prolific company back then.

Geoff Fleming wrote: ↑Wed Nov 06, 2019 2:30 pm Not sure...the ad isn't specific as to the manufacturer. It did say that the cranks featured micro-jet lubricated main bearings but no other details. Valley Core had eight different advertisements in the June '69 issue of Panorama, including the full back cover....Quite a prolific company back then.

Those were the SPG cranks; definitely not Hirth.

I still remember their silly ad copy “ ensures uniformly smooth rotation, similar to a turbine”

Martin Benade wrote: ↑Wed Nov 06, 2019 3:16 pm I still remember their silly ad copy “ ensures uniformly smooth rotation, similar to a turbine”

Love it! Don't remember it, but Love it.

The aftermarket SPG roller crank's journals are just pressed together vs. the Hirth's crank
having notched faces for positive assembly.
Racing drivers made sure the SPG cranks had their journals spot welded to prevent "slippage"!

The one I had (and which is now keeping a door open in England) was from Wellington; it had tack-welds on all press joints.

A propper built up Japanese bike race crank must have a deep weld all the way around the pressed in pins. Much better than a Hirth.

For street use, unwelded is fine on a bike?

Martin Benade wrote: ↑Thu Nov 07, 2019 11:12 am For street use, unwelded is fine on a bike?

Yes. But in racing you double the horsepower, run at redline constantly, and have erratic traction. That puts tremendous shocks through the crank. Old school roller cranks had taper fits with lock nuts but straight press fit interference fit is stronger because the flywheels don't need to be thinned to make room for the nuts. Splined fits are silly expensive, can't be positioned for truing, cause stress risers, reduce the cross section of the pins.... it just seems complicated, not elegant. Simple and functional is elegant engineering, like the rest of our 356s.