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Home > Help Needed / General Tech Chat > Hypatec pistons - increasing dish volume

Rod S

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5988 Posts
Member #: 2024
Formally Retired

Rural Suffolk

10th Apr, 2008 at 02:23:14pm

The ones from Minisport.Australia
The "good" ones (73 or 73.5mm) with nice solid castings and oil drain holes, not slots.
How much to machine out ???

This was Benross's comment in an earlier thread that I partially hijacked (as it just happened to mention those pistons).

On 2nd Apr, 2008 BENROSS said:
......retired
theres mega meat on those piston crowns you will get some good cc in there

Sorry Benross, I completely missed your comment (until searching now) or I would have followed it up at the time...

So, has anyone actually machined these Hypatecs out (or had a machine shop do it) yet, and if so, by how much and what shape?

I measure 7.3cc as bought and the dish is a shallow curve of uniform radius with a minimum crown thickness of 6.5mm in the centre but, because of the profile under the crown, it is quite a bit thicker further out (esp. in the gudgeon pin plane).
If I assume a safe limit of 5mm the most I could get by replicating the shallow curve would be 9-10cc so I'm considering a flat bottomed "U" profile instead (or very shallow curve at the bottom of the "U").

Before I waste too much time calculating what I might achieve, any thoughts please.

Rod.

Schrödinger's cat - so which one am I ???

wil_h

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9258 Posts
Member #: 123
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Betwix Harrogate and York

10th Apr, 2008 at 05:36:43pm

Don't know if this thread is any use, 998 MS Hypertecs

Fastest 998 mini in the world? 13.05 1/4 mile 106mph



On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.

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