Valve interference-solution? academic

[914efi]

I was thinking about steel sleeving 944 blocks, this made me think of the reduced geometrical compression ratio that could be used to get the same actual CR due to less heat loss through the steel (how much?). This in turn made me think about making custom pistons with valve clearance located so that the valves don't hit. This then made me wonder if just changing pistons to a version designed with enough valve clearance would eliminate the interference.

If not, I guess that explains why the factory did not do it that way, but there are some 928s that are not interference.

How much do the valves actually 'protrude' into the pistons at full lift and TDC?

Thanks for indulging the random thoughts.

[Techno Duck]

Non-interference pistons have been done for 951 engines before. The pistons on the 951 are significantly different however as they are normally 8:1 compression. With the reliefs cut into the pistons, compression was calculated to be 7.9:1.

Based on the difference in compression between the two, i would assume quite a bit of material would need to be removed from the piston on a n/a car in order to achieve non-interference.

[Porsche-O-Phile]

Depending on the size/shape of reliefs you can get other problems as well - stress concentrators and hot spots on the piston heads.

Checking the timing belt is cheaper.