[Supras] MHG's

Thu Feb 15 21:21:03 CST 2007

This has been discussed several times, so I'll just give a short
explanation:

1.  All of the cam bearing saddle wear is in the caps because the valve
springs push the buckets and shims upward, so upward force is applied to the
cams.

2.  Repair shops will want to "line bore" the saddles and caps, costly,
unnecessary, and troublesome from a standpoint of valve timing since the
cams sit lower which changes the crank to cam span.  They need to cut the
caps down to do this, so why not stop cutting (or lapping) of the cap
surfaces when the journal lash is proper instead?

3.  Take off the caps adjacent to the one to be "refinished" and use a few
thicknesses of writing paper as shims on TOP of the journals, then reinstall
the caps LIGHTLY tightnening the bolts.  That will press the cam down at the
one you want to refinish.

4.  Take off the cap you want to refinish, lay a piece of plastigauge on top
of the journal, and reinstall the cap.  Take the cap off and read the
plastigauge.

5.  Lap or flat file (carefully to insure flatness) the cap surfaces.  If
you have a surface plate, read the relative height of the flat surface at
the top of the cap first as a datum.  If not, do not take off too much metal
at one time.  If you can read cap height with a dial indicator, take off
about .001" each time until you get the feel of how much is safe to remove.

6.  Reinstall the cap, and re-read the plastigage.  You don't need to remove
the plastigage each time you take off metal.  It will stick to the cap,
journal or both and continue to compress and spread each time you retry the
cap.  But be sure to otherwise clean the cap of metal bits before again
checking it by reinstallation.

7.  Do all the caps the same way.  Move the paper shims to wherever needed
to straddle the one you are refinishing.

8.  The rearmost exhaust cap, #7, will usually be the worst.  Shimming #6
down will suffice to insure that jounal #7 is pushed down into the head
saddle.

9.  Try for .002" journal clearance.  Use the green plastigage at that
clearance, not the red type, since the green is more accurate at .002" to
.003".

10.  The frontmost journals will usually be OK.  Some engines used a soft
coating on the journals, most of which will be found worn away.  It
increases journal diameter by .002" to .003".  No one seems to know the
purpose of it.  It seems counter intuitive to use a soft coating like
babbitt against aluminum.  Instead, there should be differential hardness in
bearing surfaces, like cast iron against aluminum.

11.  Wear of adjusting shims rarely occurs.  If you have excessive lash, the
culprit is probably cap wear.

        BernieK

----- Original Message ----- 
From: "Joel Watkinson (Cars)" <Cars at xantheon.com>
To: <berniek at technicaldevelop.com>; "t72pwrd" <nholden1 at woh.rr.com>;
<Bigmacz28 at aol.com>; <SPOOLED91T at aol.com>; <Supras at supras.com>;
<supr91tt at yahoo.com>
Sent: Thursday, February 15, 2007 9:57 AM
Subject: RE: [Supras] MHG's

So, I'm looking to install some NA cams in 7MGTE. I assume it would be a
smart idea to go ahead and refinish the cam caps when I do this. What's
involved in refinishing that cam caps? Does anyone know a of a shop in
the DC area they'd trust to do the work or is it better to ship them
out? Or does the work need to be done on the head and the caps?

Thanks,
Joel
'87T still have it - still not moving - still buying more parts for it
:)

> -----Original Message-----
> From: supras-bounces at supras.com
> [mailto:supras-bounces at supras.com] On Behalf Of
> berniek at technicaldevelop.com
> Sent: Tuesday, February 13, 2007 11:52 PM
> To: t72pwrd; Bigmacz28 at aol.com; SPOOLED91T at aol.com;
> Supras at supras.com; supr91tt at yahoo.com
> Subject: Re: [Supras] MHG's
>
> 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
> > > _______________________________________________
> > > Supras mailing list
> > > Supras at supras.com
> > > http://supras.com/mailman/listinfo/supras_supras.com
> >
> >
> >
>
>
>
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>