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using 931 head on NA bottom end
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 1227
Location: Maysville, Colorado

PostPosted: Thu Mar 25, 2021 10:14 pm    Post subject: Reply with quote

When I did my 931S2 pistons I had basically 0 deck clearance and had to cut pockets. From the clay marks they are a bit deeper than necessary.

https://imgur.com/d9R2u11

https://imgur.com/7WdNwaO
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'67 MG Midget Dp
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Juho  



Joined: 03 Oct 2018
Posts: 377
Location: Finland

PostPosted: Thu Mar 25, 2021 11:20 pm    Post subject: Reply with quote

with na head?
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 1227
Location: Maysville, Colorado

PostPosted: Fri Mar 26, 2021 12:52 am    Post subject: Reply with quote

Yes, NA head
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anthonimartini  



Joined: 17 Feb 2020
Posts: 240
Location: portland oregon

PostPosted: Fri Mar 26, 2021 1:26 am    Post subject: Reply with quote

the s1 and s2 931 pistons have the same height correct? just a different bowl shape/volume? i have a nice set of s1 pistons i considered getting the ring lands machined to accept NA sized rings for reliability. i didnt consider using them for a bump in compression over the euro NA pistons. how much volume did those reliefs add to the chamber?
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safe  



Joined: 18 Mar 2017
Posts: 583
Location: Sweden

PostPosted: Fri Mar 26, 2021 1:31 am    Post subject: Reply with quote

anthonimartini wrote:
the s1 and s2 931 pistons have the same height correct? just a different bowl shape/volume? i have a nice set of s1 pistons i considered getting the ring lands machined to accept NA sized rings for reliability. i didnt consider using them for a bump in compression over the euro NA pistons. how much volume did those reliefs add to the chamber?


Whats wrong with the turbo rings?
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11723
Location: PacNW

PostPosted: Fri Mar 26, 2021 5:06 am    Post subject: Reply with quote

safe wrote:
Whats wrong with the turbo rings?


They cost One Jillion Dollahs (per slug).
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 1227
Location: Maysville, Colorado

PostPosted: Fri Mar 26, 2021 5:20 am    Post subject: Reply with quote

Welcome to my world. I bought the pistons for about $100, by the time I bought the rings, had the pistons machined for the NA rings and then got the valve pockets cut I was within about $100 of just getting a set of new forged lightweight JE pistons with rings and pins.
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anthonimartini  



Joined: 17 Feb 2020
Posts: 240
Location: portland oregon

PostPosted: Fri Mar 26, 2021 7:58 am    Post subject: Reply with quote

and they break. at least under boost. i can get them machined to fit the larger rings and use a decent set of rings for about half the price of the oem sized rings. the are a bit more efficient then the NA rings as the thinner contact area reduces friction. but ill take the reliability.
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dial67  



Joined: 07 Apr 2013
Posts: 20
Location: DeRidder, LA

PostPosted: Fri Aug 05, 2022 9:28 am    Post subject: VW Type 1 pistons Reply with quote

Did the VW pistons work well in your build? If so how much deck height? It would seem that the block would have to have considerable material removed. I am interested in using the VW pistons because they will be easy to source. I have had quite a run around trying to buy pistons.
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