How I made Piston Buttons for 20773 998 Pistons
Turbo Mini Forums

Firstly, I bought some PTFE (Teflon) off Ebay, I bought a 250 mm length of 20 mm bar. I can't remember what it cost but is was pretty cheap.

Then I got it 18 of the following diagram machined up (2 spare, always handy)



To make them fit I rounded off the heads to make them more mushroom-like and to fit with the curve of the bore. To do this I put them in the gudgon pin ends and shaped them until they were a nice fit in the bore, not too tight not too slack. I used a Dremell, but a file would do.

That's it.

These seem to work fine in our engine.

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

www.twin-turbo.co.uk

These replace the circlips completely? unlike the other method of preventing the circlips from falling out?

Good info.

I've seen the future and tbh its Pie

Yes, remove the circlip completly.

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

www.twin-turbo.co.uk

i'll give them a go on mine, cheers wil

I've seen the future and tbh its Pie

So this wil work on every pistons?? I have a set of Omegas for my 1293 S wich this would be perfekt :)

www.shag.no

The 1275 wrist pins are press fit, so if you do this Vegar, you need to ream the little end of the rods bigger.

sorry i know this is very old but why would these be better than circlips?

The circlips are prone to failure, and when they fail they take big chunks out of the side of the cylinder walls rendering the block scrap.

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

www.twin-turbo.co.uk

sorry i know this is very old but why would these be better than circlips?

because if a circlip comes out (and they often do) it scores the bore, the PTFE button wont.

is there anywhere i can buy some? I dont quite understand the diagram

Edited by miniboo on 3rd Mar, 2008.

could u use these aswell as clips?

its basically a top hat shape, so some round bar to a particular diameter, with a step in, parted off to length.

The idea is to use them instead of circlips.

but will they not wear and become slack, i was thinking you coud use them and if the circlips go nothin bad will happen?

i doubt they will wear much (if at all) inbetween rebuilds, its not just us that use this method, its a common mod, racing jags use them, nissans use them etc etc

as my nan says "everyone cant be wrong"

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

There's no real wear as they don't fit tight in the bore. Small amounts of movement isn't a problem.

You could fit both but the machining would be very difficult as the circlip intrudes on the hole in the gudgeon pin.

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

www.twin-turbo.co.uk

Does anyone have pictures of this mod? I can kind of imagine it....but just curious how it looks. How does the PTFE hold up to the temp?

Does anyone use spiral locks instead of the circlips?

It sould be sth like this, right?
Teflon will hold the temp, after all You propably have som of that on frying pan.

Attachments:

26.52kb

Correct. Remember the crap diagram I drew at the top if fot 20773 pistons. The Hypertecs hare completly different.

As It happens I received a bar of PTFE last night to turn up a new set.

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

www.twin-turbo.co.uk

fancy doing me a set for £??

Sprox,

Why have you done that with interference rods?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I guess they are honed up to make the pins floating?

Indeed they are fully floating pins.

Note, I opted for different pistons in the end

here are some i made earlier

Balls, the attatchment thing isnt working

Edited by Sprocket on 20th Mar, 2008.