Piston Q

[marc_scirocco at sympatico.ca (Mtl-Marc)]

I just called headgasket.com, and spoke with Mordy.

He says that the top compression ring has to sit 5mm below the surface into
the cylinder so the compression is good.

I measured the pistons, and the top ring sits 6mm bellow the top of the
piston, and the piston sticks 3mm out of the block.

6mm - 3 mm = 3mm

So the top ring sits at 3mm bellow the deck, which is too high.

This is getting like a show stopper to me. I'll just stick the stock 92.8mm
crank in there so I can make it to Cincy, and I'll see what my options are
next once the car runs.

Perhaps the 95.5mm TDI crankshaft would be a better fit in a tall block 2l
motor. Or just sell the crankshaft and forget about it.

I'll put this info and the crankshaft aside for now, and I'll get this thing
running with the 2l motor.

Thanks Dan for your time and info.

Cheers

Marc

> -----Message d'origine-----
> De : Dan Bubb [mailto:jdbubb@xxxxxxxxxxx] 
> 
> You know another possibility is to have the tops of the 
> pistons machined down by 1.35mm (assuming a TDI crank is 95.5 stroke).
> It won't effect the strength of the piston crown because 
> you'd only be machining the perimeter and not the center 
> which is the area subjected to the most heat and requires the 
> most strength.
> OTOH, the top piston ring can't be too close to the top of 
> the piston. There are possible overheating effects and it 
> will also weaken the top ring land and any detonation or 
> pinging could possibly collapse the top ring land (top
> perimeter) of the piston clamping the top ring and 
> eliminating its sealing ability. You'd have to consult 
> somebody with more experience than me on something like this. 
> I only know that turbo pistons, subjected to higher pressures 
> and more heat, routinely have the top piston ring further 
> down the piston. Perhaps somebody like Colin at TT would have 
> some experience with this.
> Dan
> 
> From: "Mtl-Marc" <marc_scirocco@xxxxxxxxxxxx>
> To: "'Dan Bubb'" <jdbubb@xxxxxxxxxxx>; <scirocco-l@xxxxxxxxxxxx>
> Sent: Monday, May 07, 2007 6:53 PM
> Subject: RE: Piston Q
> 
> 
> Thanks for the info Dan, I'll call my machine shop so they 
> can machine/balance my pistons/rods.
> 
> Here is what I had in mind for headgasket http://www.headgasket.com
> 
> Cheers.
> 
> Marc
> 
> > -----Message d'origine-----
> > De : Dan Bubb [mailto:jdbubb@xxxxxxxxxxx] Envoy? : 7 mai 
> 2007 09:47 ? 
> > : marc_scirocco@xxxxxxxxxxxx; scirocco-l@xxxxxxxxxxxx Objet : Re: 
> > Piston Q
> >
> > Well, technically the piston should have a shorter pin 
> height, by half 
> > the difference in stroke between the TDI crank and the 2.0L crank, 
> > 1.35mm I think.
> > IIRC the ABA steel head gasket is 1.65mm thick compressed.
> > So, two of them stacked would give you about 3.3mm or 1.3mm 
> above your 
> > piston which is just about the right piston to head clearance.
> > I don't know if that's a good solution though. I'd wonder how well 
> > they would seal if the embossing on the two gaskets didn't line up 
> > close enough.
> > If you go with a copper gasket measure the piston 
> protrusion from the 
> > block using a micrometer or caliper. Add .040"minimum to 
> that for the 
> > final gasket thickness.
> >
> > As a minimum, after you modify the pistons for oil squirter 
> clearance, 
> > you need to get them rebalanced. You can modify them 
> yourself, but I'd 
> > be striving for an identical cutout in all the pistons.
> > Dan
> >
> > From: <marc_scirocco@xxxxxxxxxxxx>
> > To: <scirocco-l@xxxxxxxxxxxx>
> > Sent: Monday, May 07, 2007 8:47 AM
> > Subject: Piston Q
> >
> >
> > >I installed my TDI crankshaft in my 9a block this week-end 
> hoping to 
> > >get 2.1l of 8v power ;-)
> > >
> > > The crankshaft spins freely without hitting anything, so
> > that is good.
> > >
> > > However, there are two snags as I see it.
> > >
> > > 1. the piston stick about 2mm out of the cylinder at TDC.
> > > Can I safely run 2 head gaskets to bypass this problem?
> > > I have seen a shop in the norteast that can make me a
> > copper head gasket, Perhaps this can be a more permanent 
> solution in 
> > the long term.
> > >
> > > 2. on the bottom stroke, the piston hit the oil squirter.
> > > There is already a notch in the piston skirt for the oil
> > squirter. But I need a bigger notch.
> > > Do I need a machine shop to do it or can I just enlarge the
> > notch at home with my die grinder?
> > >
> > > Thanks
> > >
> > > Marc
> > >
> > >
> > > _______________________________________________
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> > >
> >
> 
>