Valve Guide Removal

[Henry Schmidt]

Originally Posted by 88911coupe

This was one aspect of my rebuild I was not even going to try myself. I just was too nervous to mess something up badly. This is where someone like Henry is extremely valuable. I actually had all this work done by Competition Engineering and it really was not too expensive in the whole scheme of things.

Quite frankly, Competition Engineering is a great choice. I like Walt and he does great work.

[MBEngineering]

HI
As Henry has noted, do NOT take it that the guides are strait no mater where you live, as there are shouldered guides supplied in the UK, so check what you are working with






UK supplied guides, and to quote Henry if I may, "never assume any thing"

regards mike

[crummasel]

Originally Posted by 304065

Half of all aircooled Porsches EVER sold went to California.

Half of those went to Southern California.

I think it highly likely that there are a few of Henry Schmidt's engines in Europe given the Euro exchange-- lots of great California cars are making their way back to Germany.

Absolutely, i would'nt doubt that basically while not knowing if to that extent. ;-)

Anyway it has just been an ironic replica on the slightly high and mighty attitude, just kidding.

A very long time ago a machine shop managed to crack one of my first Porsche motorheads by pushing the old guides to the valve side, probably caused by trying to push the slightly widened lower area of the guide and the charred dirt around through the bore.
After that i have "developed" my own methode (without knowing any forum) to do it and it was nice to see that it is exactly the same like Henry's, just in the other direction.
Good thing with this methode is that the old guide is not going to get compressed but streched. I made a huge amount of heads this way without any issue.
But for sure not by far as many as Henry. ;-)

Still trying intellectually to capture the monkey and coconut story...

@mike
clear, but these ones you can identify and messure. Anyway a good strategy to messure and to think prior to applying force... ;-)

[Dick Shift]

Just my two cent's
I heat the heads to 350 before doing the above. As Porsche recommends. That insures the thin casting around the valve guide boss in the intake ports will not crack or chip off. I learned this the hard way. You don't need to. Aloha, DS

[john walker's workshop]

of the hundreds of heads i've done, i never heated one. with proper technique, the guides come right out. i used to do vw guides with the tap and bolt, but on 911s i step drill and air hammer them out with a light trigger finger. on the air hammer bit, it's a good idea to taper the step so it doesn't catch the guide bore as you run the guide out. on installation, spray some WD or some other similar product in the bore and on the guide before installing. makes them go in smoothly. always mic the old guides and the new ones so you don't inadvertently run in an oversize by mistake.

[Dick Shift]

And,
Put the new valve guides in the freezer the night before. With a little anti seize on the new guides before installing...... in like butter.

always mic the old guides and the new ones so you don't inadvertently run in an oversize by mistake. Good idea!
__________________

[aquazulu2]

I knew if I looked long enough I would find the DIY answer to valve guide removal and recognize the pros when I saw them. Thanks for posting this helpful thread. The end of the discussion got a little heated and got thrown in the freezer a few times, which may have taken away a little from the final solution; installation of the guides. but great technique! I believe. I will try the old tap, bolt and drive out method, as agent smart would say.. Great idea. Printing as an addendum to my bentley manual..

[rtroy]

Originally Posted by nocarrier

Is there a tool to set the correct depth when installing a new guide?

Also, what is the right amount of interference for the guide and the head? Shouldn't that be measured and the guides turned to fit the heads?

(The bolding emphasis was added.)

This is a great question that everyone has ignored, and is, in fact, the reason I've come here to look around today... I would really appreciate if some of the old timers spoke up and shared about this!

Some many years ago (late 1980s), I did a number of engines worth of valve guides and seats and had some good advice from others. (I was an apprentice of David Brown at Weissach Engineering, Colorado Springs, now long gone, unfortunately.) I have a mill and a lathe and I got some numbers from him and his machinist of the form:

"For steel seats in an AL head, your theoretical best interference fit is X for every Y bore. Calculate your intake seat fit with Z% more crush, but don't go beyond W% or you risk cracking the head. Bronze guides in an AL head should have a crush of X for every V of bore, but there's always a minimum of L, and intakes should always have J more crush. If it's a silicon bronze guide, alter this by K."

And I did guides and seats like this for some 3 years or so and it all worked fine. It's worth noting that I used the rather unorthodox strategy of installing (especially valve seats) by using a quart thermos of nitrogen, about 1/2 full, and then dropped the seats / guides in to a room-temp head and it all went in without a problem. I used the "stretch em out" threaded spring end, drift through to the bolt-in-threads from seat side strategy for removal, and used the old guide ID as a BIG help on determining where the existing guide bore may be at since the bores in the head can be hard to measure accurately with a bore gauge... If you have the old guide, and can get a feel for how hard it is to remove, you can build a sense for how relatively tight or lose it is in the head and thereby have a good feel for the current interference fit.

But doing heads was a pain in the but, so I farmed the work out starting around 1990 and now, starting around April this year, that shop isn't doing them any more, and I've lost track of my notes. ... About two weeks ago I literally bought over a ton of Porsche parts and I now have added four engines to rebuild on my already extant queue of at least four I was already doing, so that's a LOT of head work, and now's the time to figure this out! What's worse, some of these heads have the guides already removed so, no help there!

Any input?

[ed mayo]

All the guide fit numbers you want are in the 'little spec books'