5 Mk I incl Gordini Renault R5 Turbo piston crown height

[Stefan]

Hi!

I´m re-organizing the garage and come across parts that I´ve had stashed away for ages. Among the Renault R5 Turbo-stuff there were a few sets of Mahle 80 mm pistons from an earlier R5 Turbo engine build. The sets came as spares with a complete works-engine, all dating back from the 80´s Group B-cars. When I measure the sets I notice that there are three different piston crown heights. I did a cheapish measure and measured from the uppermost part of the gudgeon pin hole to the top of the piston crown. The measurements read as follows:

16 mm (5/8")

21 mm (53/64")

22.5 mm (57/64)

You see a few of the psitons in the pic. I´m no longer in to turbo builds, so I was hoping that some of the sets were for the atmo-engines, given the great differencies in crown height.

Does anybody know the correct heights for Turbo v/s Atmo pistons ? Any help appreciated

 

[gordini stu]

If they are flat tops all turbo pistons , don’t quote me but at a guess I’d say the shortest ones are from a over stroked 1500 cc engine. The others may be standard and lower compression for higher boost , loads of more knowledgeable people on Some of the face book pages

 

[Stefan]

Thanks for your reply. It supports what I´ve read, but don´t really know for sure, that flat tops are indeed for turbos only. A calculation of cc points to turbo compresssion as well, so I´m sure you´re right. Meaning I have like three sets of prefectly usable German-made pistons to absolutely no use Just my luck.....

Would they be of use to anyone? I checked and found new rings at decent prices...