[Vwdiesel] Used Pistons/Head

[James Hansen]

I think it's around 450F for an hour Val, then turn off heat and let cool
overnight with the oven door closed.  Might want to do that outside, unless
you are single (or wish to renew that status).
Trick is to get a large enough FLAT section of steel, preferably cast iron.

Loren, isn't what you describe is a head that is warped in more than one
dimension, like a mushroom cap, warped not just across the length, but
across the narrow aspect as well.  I've never done it myself, but have been
told my a couple different crotchety old German mechanics that baking is the
best way. One guy had just that, an old leaky dishwasher and an electric
oven in his shop. Ran it on a cycle with lots of dishwashing soap, then
baked it.  Had a big chunk of milled cast to bolt it to.  This is the same
guy that heat treated, then lapped all his aircooled engine cases by hand on
a 1" thick piece of glass before align boring them. He was FUSSY. Did I
mention crotchety too? Oh yeah...
-James

> -----Original Message-----
> From: Val Christian [mailto:val at swamps.roc.ny.us]
> Sent: Thursday, April 29, 2004 11:15 AM
> To: James Hansen
> Subject: Re: [Vwdiesel] Used Pistons/Head
>
>
> What's the bake temperature for an Al head?
>
> Val
>
> >
> > As said, different machine shop.
> > The best shops use cubic boron nitride cutters now, and the
> cutter cares not
> > a whit how hard it is. Besides, being in the combustion
> chamber, unless a
> > very special steel, it will be soft. If the shop is using older insert
> > technology, you don't want your head milled by them.  The surface finish
> > will not be smooth enough to seal properly on what is considered to be a
> > high performance sealing surface. Only way to get it smooth
> enough is with
> > CBN, or diamond cutters.
> >
> > Proper way to get rid of warp actually is to clamp the bare
> head to a flat,
> > and bake it to relieve the stress and get the warp out.
> > Serious, not joking.
> > -James
> >
> >
> >
> > > -----Original Message-----
> > > From: vwdiesel-bounces at vwfans.com
> [mailto:vwdiesel-bounces at vwfans.com]On
> > > Behalf Of E. J. Gilbert
> > > Sent: Thursday, April 29, 2004 9:31 AM
> > > To: vwdiesel at vwfans.com
> > > Subject: [Vwdiesel] Used Pistons/Head
> > >
> > >
> > > Hi Guys,
> > > I am up to my elbows in a Jetta Turbo Diesel engine.  So far, the
> > > head is warped and cracked between valves. There is a definite
> > > ridge at the top of the cylinders.  Machine shops say that they
> > > cannot flatten head due to the very hard prechamber inserts.
> > > Does anyone have used oversized pistons and a head for sale?  Any
> > > other ideas would be appreciated.
> > > Thanks,
> > > E.J.
> > >
> > >
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