[alfa] RE: V6 valve guides

[AlfaRs@xxxxxxx]

Guys thanks for all the help and tips and a few more questions.


Ron Horowitz wrote

>Hmmm... Only at WOT or does it smoke when you fire it up in the morning,
>too?

I should have added that it does puff a bit at startup.  The oil consumption 
is 
getting on the high side.  I've checked compression across all cylinders wet 
and dry and it is very good so I'm pretty sure that the rings are good.

>You don't have to pull the heads to do the seals. Pull the cams and plugs,
>bring the pistons up to TDC, put rope in the holes if you have to, and take
>the valve springs off.

The heads are coming off because of a blown head gasket not because 
of the guides otherwise I would leave well enough alone.  It's not really 
THAT bad.

>Define typical tools. For the seals, you'll need a spring compressor, but
>that's about it as far as "atypical" tools.
>
>For punching out the guides, you can make do with whatever. For seating
>them to the correct installed depth, you'll either need the factory tool or
>access to a lathe to make your own (in which case you can vary the
>specification to suit yourself.)

I haven't worked this one out yet.  There use to be several suppliers that 
sold the factory tool but I don't know if any still do.  If not I've got 
access 
to some really nice machine equipment and also to some great machinist 
so I'm sure something can be made up if needed.
 
>You'll probably want to recut the seats. If so you'll need a seat grinding
>rig. I bought a pretty nice Siuox seat grinding set-up and a Van Dorn valve
>grinder.from a mechanic who no longer did valve jobs (all he does now is
>"driveability".) You'll want to buy good used seat and valve grinders if
>you can find them as these items are _quite_ expensive new. Kwikway,
>Snap-On, and Serdi are also common makes....

This is the part that worries me the most.  Having to recut the seats makes 
for a major PIA.  This is mostly why I asked this question.  Do the seats 
normally need re cut or do the guides maintain a true enough centerline 
that I can work around this?

I'm really not trying to cheap out on this but I figure that at 120k miles 
I'm good for 40-50k more before I'll want to do a complete rebuild.

Roger wrote:

>You can hone your own guides. I do.
>When honing the guides to size use a BALL HONE (9mm) and NOT 
>A REAM. You will also have to recut your seats to match the new 
>guides. Re-cutting the seats re-establishes concentricity between valve 
>guide and valve seat which is absolutely IMPERATIVE.

Ron mentioned honing also.  I'm not familiar with this process.  I assume 
that this an abraidable "ball".  Is it used by hand (like a ream) or turned 
by machine (like a cylinder hone)?  Is it run dry or with cutting oil?  Do 
you 
know of a good source?

Ethan Schartman wrote:

>i've done it (twice,(&$^#!).

As a wise man once said "I hope to learn from your mistakes" :)

>well, you could do the seals without doing the guides,
>as long as they are in good shape. 

This is an option but my experience with V6's says that at 120K just doing 
seals won't last long.  The original guides always seem to go at 60-100k.

>mostly. you'll need a tool to remove the valves and
>cam pulleys (mark's alfa twiki has a nice super simple
>way of holding the cam pulleys). give me a hollar if
>you have trouble locating special tools in your area. 

I've done this before without the special tools but thanks for the tip 
I'll check out Mark's site
 
>i never bothered to replace or recut my seats, if
>there is no scoring or divit that run the entire
>seating surface, then don't worry too much (IMHO) -
>just lap. and don't forget to secure your liners (not
>doing this ultimately led me to re-ring my engine:)

How did it hold up without recutting the seats?  

>if you really are pressed for time, buy 13 guides just in
>case you mangle one:)

Excellent advise!!


Rich Wagner wrote:

>Replacing guides requires machine tools that most home mechanics don't own,
>including a press and a boring mill. Also, the tolerance requirements for
>alignment and concentricity of the new guide are best handled by an
>experienced machinist. Most decent machine shops can handle this kind of
>work without a problem. Most home mechanics can't.

I should add that I am a little better equipped than the average shade tree.  
I've 
got a press, drill press, parts washer, etc..... I also work for a company 
that 
overhauls jet engines.  We've got 35 or 40 Bridgeports alone. We do 
everything 
from CNC, CMM, EDM, to plasma spray and laser welding.  What we don't have 
is a valve seat cutter #$%%!

>That said, are you SURE you need new guides? There is only one way to
>tell. Measure them. (Email me if you'd like to know how.) It's entirely
>possible that the guides on that engine are still within spec. 

True but Alfa V6's are a bit hard on guides in my experience.  That is where 
most of the normal oil consumption comes from.  I just can't see tearing down 
the head to the point of measuring the guides and not replacing them.
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