C J Murray wrote:
Wil Mittelbach wrote:
CJ -
Perhaps a naive question; but couldn't one just shim the cyl/crankcase interface at 4mm rather than shortening the rod, and use standard short skirt 3-ring JE pistons??
- Wil
That is a good question. In my motorcycle racing days we did just that, sometimes. We weren't allowed to change the stroke, just like in vintage car racing, but some engines benefitted from a longer connecting rod. Generally a short rod offers more low rpm performance while a long rod is best at high rpm. Short is around 1.5 x stroke and long is around 2.0 x stroke. Most engines designed for production cars have fairly short rods for easy packaging(shorter engine) and low rpm performance.
The problem with the 356 is that the engine tin and the body of the car means that a lot of work would be required to make the engine wider, even just 8 mm. I don't think most 356 owners would want to make those modifications. Motorcycles are easier because there is no tin but sometimes there is not enough room in the frame for a taller engine.
The original Porsche design of placing the oil ring below the piston pin has to do with engine width and rod ratio. It was not a good idea but they had a reason they did it that way.
CJ -
Agree that 356ers may be reluctant to trim engine tin to accommodate shimmed cyls as possible deterrent for shimming the cyls, as are stroke limitations (per cam interference).
Per your motorcycle days, I also recall early Harley cruising hot-rod bikers with stroked engines having about a 1/8+" aluminum plate under the "jacked-up" cyls, plus some also converting their "stroker" bikes to a foot operated shift and/or "suicide" clutch.
- Wil