[Supras] MHG's (now cam oiling)

[Jeff Mohler]

I dunno..I like to see clear evidence of failure across the board (like
BHGs) before I call something a design flaw.

Sorta like when you saw motor mounts as a huge flaw when you started on your
car..theres no issue, just YOU had bad ones, and after 20+ years, they had
the right to be bad.

Your low miles engine with severe erosion is not typical to the rest of us,
even with 100s of 1000s of miles.

On 2/13/07, berniek at technicaldevelop.com <berniek at technicaldevelop.com>
wrote:
>
>  Jeff:
>
>     My JDM did not have that many miles on it either.  The cylinders were
> not worn more than 1/2 thou or so, and the main and rod bearings were in
> like new condition.
>
>     However, the camshaft journal caps were worn, especially on the
> exhaust side, where the rearmost ones plastigaged at .006".  The problem is
> the lack of oil feed to the head, and the fact that all of the journals are
> cross-drilled.  As I'm sure you know, oil is fed into the hollow cams at
> only the front journal.  As a little wear occurs, there is less and less oil
> for the rear journals.  That is especially true at high speed because the
> oil tends to be thrown out of the journals increasing as the square of
> speed.  So less and less oil is available for the rearmost journals.
> Moreover, the oil passages in the block and head which feed the cams are
> small.
>
>     As my rebuild wears, I'll probably refinish the caps every 20K miles
> or so.  But the thought did occur to me to drill into the 7th exhaust
> journal support in the head, intersecting with another drilled passage on
> the exhaust side, and run an external oil line to feed at least the exhaust
> cam from both ends (with a groove machined in its rearmost journal).  But
> one problem with doing that is the reduction in head saddle journal support
> width.  It reduces down directly under the cam journals, so putting an oil
> feed hole in the rearmost one and grooving the cam journal itself for oil
> feed might be self-defeating.
>
>     Strange that the bottom end is built like the proverbial outhouse
> (with proper oil pan pickup provisions), but the top end oiling provisions
> are far from the best.
>
>             Bernie
>
> ----- Original Message -----
> *From:* Jeff Mohler <speedtoys.racing at gmail.com>
> *To:* berniek at technicaldevelop.com
> *Cc:* t72pwrd <nholden1 at woh.rr.com> ; Bigmacz28 at aol.com ;
> SPOOLED91T at aol.com ; Supras at supras.com ; supr91tt at yahoo.com
> *Sent:* Tuesday, February 13, 2007 11:58 PM
> *Subject:* Re: [Supras] MHG's
>
> Ya..but were talking a JDM import motor, with about 30k miles on it..and
> it's sat on the floor for 12yrs.
>
> It aint worn..its just a _mess_.
>
> On 2/13/07, berniek at technicaldevelop.com <berniek at technicaldevelop.com>
> wrote:
> >
> > Higher than normal compression pressures can also be due to increased
> > valve
> > clearance.  The cam opening and closing ramps are very gentle, but at
> > cranking speed, a few thousandths less clearance can mean quite a bit.
> >
> > As stated in the past, the cam journal caps wear and cause excessive
> > valve
> > lash before the shims wear.  The caps can be refinished.
> >
> >         Bernie
> >
> >
> > ----- Original Message -----
> > From: "t72pwrd" < nholden1 at woh.rr.com>
> > To: <Bigmacz28 at aol.com>; <berniek at technicaldevelop.com>;
> > <SPOOLED91T at aol.com>; <Supras at supras.com>; <supr91tt at yahoo.com>
> > Sent: Tuesday, February 13, 2007 8:08 PM
> > Subject: Re: [Supras] MHG's
> >
> >
> > > Carbon build up.
> > >
> > > -Nick
> > >
> > > ----- Original Message -----
> > > From: <Bigmacz28 at aol.com>
> > > To: < berniek at technicaldevelop.com>; <SPOOLED91T at aol.com>;
> > > <Supras at supras.com>; < supr91tt at yahoo.com>
> > > Sent: Tuesday, February 13, 2007 7:21 PM
> > > Subject: Re: [Supras] MHG's
> > >
> > >
> > > > BernieK, are you using the 2.0mm also or some other side?
> > > >
> > > > Question Group: I got a JDM 7MGE and checked the compression with
> > two
> > > > different gauges.
> > > >
> > > > Both are reading 198 to 200PSI on every cylinder. What could be
> > causing
> > > > this?
> > > > The spec is around 150PSI.
> > > >
> > > > Any idea's?
> > > >
> > > > Joe Mac
> > > > 89N/A
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> > >
> > >
> > >
> >
> >
> >
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>
>