1.7 litre 90 mm Pistons

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1.7 litre 90 mm Pistons

Post by HotelRomeo » Fri Oct 05, 2018 6:15 pm

I need to find some 90 mm forged pistons with a compression ratio of about 10.5:1 for a 914 historic racer. JE dont have any off the shelf and waiting to hear back from Wiseco. Any clues?

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Re: 1.7 litre 90 mm Pistons

Post by raygreenwood » Wed Oct 10, 2018 12:26 am

Which 914 was this? Historic....I assume restoration?

None of them...type 4 based had forged pistons. That being said.....if you can find some of the original 1.7L , domed 90mm pistons.....trim the cylinders or the case deck....because the deck height to the pisyon edge from the factory was betqeen .069" and .079".....bring it down yo about .040". then flycut just a bit...bit do not remove the excellent quench dimple in the 1.7L heads.

Without the factory head gasket...and base shim....the stock 8.2:1 increases to about 8.5:1. Get rid of the excessive piston edge deck ...say....by trimming the cylinders or case deck....and you are at about 9.0:1. Flycut a little from the chamber...and you can probably get 9.5:1 without much work. Ray

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