Date: Mon, 29 Dec 2003 08:43:51 -0600
Reply-To: Jim Felder <felder@KNOLOGY.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Felder <felder@KNOLOGY.NET>
Subject: Re: rebuilding your own heads
In-Reply-To: <20031229140601.92427.qmail@web21001.mail.yahoo.com>
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I've rebuilt a number of cast-iron heads, which tend to be relatively
easy, especially if you owned the car they are in and know what has and
has not happened to them.
If yo don't know if a head is warped or leaking, you should take it to
a shop for testing. They'll take the springs and valves out, but this
is something you should do yourself to preserve the order of the parts.
Number 1 cylinder I and E valves and springs should be kept together,
say in a board marked with cylinder numbers and drilled for valves with
corresponding nails for springs.
A dremel or air tool will help clean deposits out of the chambers and
passageways. It doesn't hurt to smooth up the passageways if you have
time to kill at this point.
If the seats and valves are good, then you will know how everything
must go back. If they need replacing, knowing which seats and valves go
together helps the detective work.
There are various means of testing the strength of springs, they should
match within spec. A ship probably isn't going to give you the benefit
of the doubt, they will charge you for a new set rather than go to all
that trouble.
With the springs out, the (matching) valves and be reinsersted into
their respective guides for a wiggle test, and if a dial indicator on a
stand (clamped to the head) shows that the valve stem wiggles out of
tolerance in the guide, the guide must be pushed out and a new on
pushed in and reamed. The valve stems may be worn down but not likely,
they are measured with a micrometer.
Once new valve guides are pushed in to the prescribed depth (exactly,
and without damaging the head by excessive pushing on it) then they
must be reamed, and in some cases a seal must be installed, often with
a special tool.
A professional should look at the seats and valves. If they're OK, a
nice job of lapping is in order. This is a fairly easy procedure that
uses a variety of special tools you can get at a parts store, they all
come with instructions so I'll skip lapping.
If the seats and valves are not in order, they will need regrinding or
replacing, and a shop should make that call. Replacing seats is not
something you can do yourself. Doing a good job of grinding is not
something you can do without specialized equipment, either.
In either event, the valves and seats will require lapping.
Now it's time to re-assemble. For every type of head there is a gadget
to remove and assemble the valve springs and put the retainer clips
back into place. For overhead cam engines, there's the assembly of the
valve mechansm, and for pushrod engines there's reinstallation of the
rocker shaft and rockers, all according to your workshop manual.
I've probably left out a thing or two but this would be the main stuff
to be concerned with.
You can do most of that yourself, but it's a lot of work, and takes a
number of special tools. Except for the valve grinding stuff, the tools
are pretty cheap.
If you make a mistake or do an inadequate job, though, you're risking
the heart of an engine rebuild. This is especially true if your engine
has high miles on it.
Most people are much better off going to a good rebuilder.
I don't know how much a rebuild would cost (varies a lot by type of
head, availability of parts, and quality of work). The lowest price
will almost assuredly not be what you want.
Jim
On Monday, December 29, 2003, at 08:06 AM, Scott W. wrote:
> Has anyone done this? I mean aside from maybe needing
> a machine shop to do a few things, I would think a
> person could do most of it themselves with a few extra
> tools. Does anyone know of a good way to get the valve
> springs off? How much do shops usually charge to
> rebuild heads? thanks
> Scott w.
>
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