Restoration of a 1960 Porsche 356 Super 90 sunroof coupe.
I had removed the pistons from the engine, thinking my machinist might be reworking them. Having abandoned that idea, the pistons were put back on the connecting rods today. Ring gaps reset. I’m back to the single 1mm copper cylinder base gasket.
After a lot of consternation, I shipped the head off to a well known Porsche machine shop for a second machinist opinion if you will. Unlike my original machinist, they indicated they wouldn’t consider machining the pistons. They did think they could improve the head squish angle. They might get into the valve seat, but …
The results of measuring my heads, clearances, and compression has given me a lot of anxiety. In consulting with my machinist, his advice has been to use thick shims to avoid interference and run with it. Uncomfortable with some conflicting info and not knowing how to proceed, I used a metal contour gauge to try …
I guess measuring the squish angles in the head was not something our machinist normally does. After much hand wringing, and some emails with our him, I took the head back to him for review. In short he wasn’t comfortable modding the combustion chamber any more, for fear of getting into the valve seats. The …
I have hit a wall in my assembly. The concern being that I’m seeing geometry between the head and pistons that I don’t believe is intended. In short, I think the conical part of the piston dome be parallel to the angle of the head. I think the discussion on the 356 Registry Forum confirms …
Given the results from the 1.0 mm cylinder base gasket were not really desirable, I took another run using 3 x .25 mm (.75 mm total) gaskets. Results were, well, different. Deck height is still quite high (1.67mm average), compared to the 1mm ideal. Compression ratio at 9.31 average is pretty much at the upper …
After taking last weekend to cc the heads, check clearances with clay and take measurements, I have calculated that with a 1.0 mm cylinder base gasket: Deck height is ranging: 1.82 – 1.92 mm; I understand that 1.0 mm or a little less is desired Compression ratio range: 9.02 – 9.21 (9.10 average). I understand …
Today I got on with the heads. The cylinders came first, and affect head clearance and compression measurements by way of the copper gasket that goes between the case and cylinder. The Harry Pellow book has a reference table suggesting 3-6 shims (of .008-.01 inch thickness each) as a starting point for those using Japanese …
Today I measured the Cylinder Head Combustion Chamber Volume. Also known as cc’ing the heads (cc = cubic centimeters). This is a process whereby we physically measure the volume of the combustion chamber. You have to use this science lab setup looking setup with a buret. Nice intro video on YouTube. You also need a …
A major milestone today, as the cylinders went on. It was not without its challenges. First off was the ring compressor. When you follow this sequence of engine building (i.e. Harry Pellow preferred method): The rods on the crank The crank in the case The pistons on the rods you get a scenario that dictates …
