New pistons for a '56 Super

[Edwin Ek]

I would like to use the original cylinders with chrome plating and dimples- they are in great shape. Can you use, for example SC pistons, or is the rate of expansion too dissimilar?

What are alternatives? Boosting the compression ratio would be nice.

[Jacques Lefriant]

Hi
what heads are you planning to use? the expansion rate is not a problem since the cylinder grows faster than the other ones. be careful what rings you use and the big picture is you won't gain/save much.
j

[Edwin Ek]

SC heads, 40 Solexes. Idea is to get to SC horsepower (95) easily.

[Alan Hall]

Other issues: be sure to check diameters carefully, the aluminum cylinders ran with very tight clearances since piston and cylinder expanded at approx. the same rate and there were a range of matched sizes as shown in spec book. As I recall the nominal diameter difference was less than 0.001 inch. Also the chrome cylinders do wear and can develop a ring ridge which you can't remove with a ridge reamer, if you have a ring ridge you might break the rings of the SC pistons. As Jacques indicated you would need to run plain cast iron rings, no multi-piece steel rings and no chrome rings, might be hard to find or not available at all.

[Harlan Halsey]

I faced the same issue with my Carreras year ago. I would suggest that you get modern pistons made to the compression ratio you want and fit to a clearance of .001"or slightly less. I talked to Total Seal, told them what I was doing, and settled on the 3 ring 911 ring widths. That works for me.

BTW: when Chuck forge rebuilt the engine in the Von Neumann Red Car, the pistons would drop easily into the cylinders with everything at RT. But if you held the pistons in your hand for a few moments they wouldn't go in. He thought I was chicken for specifying a whole .001" clearance. There is a potential problem of slow ring break in with the chrome cylinders. Chuck solved that problem by mounting the new rings on a dummy piston and cycling them in an iron cylinder so that they were round before they were installed.

I think pistons running zero clearance in chrome lined aluminum cylinders were one of the things which initially attracted me to Porsches way back then.

[Edwin Ek]

I think pistons running zero clearance in chrome lined aluminum cylinders were one of the things which initially attracted me to Porsches way back then.

My thought exactly. When I first met my mechanic, in 1986, he showed me some interesting early parts. I was only familiar with C cars then. One of those parts was a cylinder with chromed bores and dimples. I couldn't believe how high-quality that part was and how cool it looked. I was hooked.