Letter 15551

Nikasil liners-pistons compatibility

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I have a Porsche 4 cylinder engine (968) with Nikasil cylinder liners. I want to install a low compression piston set but none of the top aftermarket piston makers manufacture this kind of piston, and Mahle the original supplier can no longer manufacture those. Which are the specifications for a piston to be compatible with the Nikasil liners? Can I use a regular piston and give them a special coating? If so, who can do the coating?

Thanks very much.

Angel L. Martinez
- Utuado, PR, USA

Angel,

I believe that the problem is not the pistons themselves, which are made of aluminum (I guess). I would rather look at the rings. If they have a chromium plate on the OD, it might damage and scratch the nikasil of the inner bores. If you can get non-chrome plated rings, that will be much better. If not, you can probably afford to dechrome one and measure how much diameter you lost with the gone chrome and compensate it with oversized rings or simply live with it. One way to de-chrome is to immerse the ring in Muriatic Acid [link is to product info at Amazon] until gassing stops. Remember, the problem are the hardness and mating characteristics of the rings to the liners.

Good luck,

Guillermo Marrufo
Monterrey, NL, Mexico

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