[Vwdiesel] homemade valve compressor

[pmdolan at sasktel.net]

Even though you can get away with straight press-in, press-out, it is definitely not a good thing to do.  The heads gall the head bore a little bit every time you press through.

The correct way to remove a bronze guide is to "core" drill it first.  I am not home (in China now), so cant run out to the shop to check the size, but I just use a US size drill bit just about 0.020 in. on the diameter under the OD of the guide.  I think it is 7/16 of an inch for VW - you will know you have it too big if the pressing land made by the coring bit breaks out.  Chuck it up in the lathe (or even a drill press) and grind a pilot into the centre at the tip (a short length of 8 mm dia).  Using a die grinder, knock all of the sharp edges off of the flute of the pilot, and then grind a bit of free angle into the flat land to make a cutting edge.

Run the coring bit within 10 mm of the end of the guide (from the chamber side for guides with a shoulder or from the valve cover side for straight guides (not w/c VW).

Then you need to make up a press tool (or even a driving drift if you dont have a press) that is just under the coring diameter, and shove the shell out.  When the load is put on the bottom of the guide, which is little more than a very thin wall tube by now, it will shrink and come out easily with absolutely no damage to the guide bore in the head.

Pushing on a complete, full diameter guide from the same end that has to go through the head will expand the guide in the bore, and maybe even upset a bit or flare the end where the press tool is incontact, and will/can do severe damage.  This is why in the old air-cooled days, you could buy guides in several oversize ODs - a LOT of mechanics just pounded the crap out of them and did a pile of damage.

Hope that is of some help

Pat 

----- Original Message -----
From: Marcel <mygroups at websworld.org>
Date: Thursday, November 25, 2004 10:45 pm
Subject: Re: [Vwdiesel] homemade valve compressor

> LBaird119 at aol.com wrote:
> 
> >   Drilling and maching guides is cast iron work (domestic V-8's 
> and such).  
> > Most aluminum have silicon bronze or phosphorous bronze (I 
> think) 
> > guides, which are generally press in and out.  Cast ones neeed 
> drilled, 
> > pressed, shaped and reamed. If you have the tool that fits all 
> the way 
> > down the guide, when you press or drive then in, then reaming 
> very 
> > well may not be needed as the tool holds the dimension.  
> Otherwise 
> > you need an 8mm reamer.  I've found that you use a good 
> lubricating 
> > oil for the intakes and something very light or dry on the 
> exhausts.  
> > You want the exhaust guides a tad more loose than the intakes to 
> > start with.  
> >   I can see why you'd test with a new valve.  The exhaust stems 
> > wear.   Most that I've checked were tapered to .003" of wear.  
> Not 
> > much of a test of the guide with a valve like that!
> >      Loren
> 
> Well at least if they're tight with an old valve, you're in the 
> clear. 
> If they are loose... then try a new valve to find which is worn. 
> Usually 
> the guide first though, in case of bronze guides which are 
> generally 
> softer than hardened steel valve stems.
> 
> Marcel
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