I am redoing my heads, yes myself. I have a machine shop and all the tools I need to do the job. If not I can make them.(besides if I mess them up they are only 1.7 heads and I have a spare set)
I dismantled one head today, glass beaded it and gave it a good inspection. The seats are in great shape but the guides are outside tolenances. Actually I have never seen valves so sloppy in an head in an engine that actually ran.
Here are my questions.
Are there any tricks I need to know before I start pressing the old guides out?
Do they come out from the top? (as I would expect)
Was there a sealant from the factory bonding them in?
Should the heads be heated in an oven to warm them up before pressing?
If so, to what temperature?
Should the heads be heated (and guides cooled) before installing them?
I have searched for tech articles on the subject but come up dry.

Tx for your help.
Doug

Ah, so oversized guides refers the outside of the guides.

Tx
Doug

I hate to disagree with Brad but I've done thousands of type 1 and 4 guides.

First you must always core the guides. Drill (core) them as much as you can, (75%) this will relieve the press fit.

I never remove the guide out through the top (VC) side.
I cut the top (VC side) off of the guide, as it has a step in it and then I core and tap it out through the valve opening.

The logic behind this is if you do it the other way you drag carbon and crap up through the guide bore, not good for it. Cored correctly it will just tap out with an old bolt. I've never heated for removal.

For install I have a special bit for my air chisel and I just drive them in cold. You start them in by hand for the first bit. They do collapse a couple of thousands so I run a ball broach though them as necessary. I measure everything of course.

Doing it this way on original guides I only need to use a STD replacement guide 75%+ of the time. Most oversize guides go into heads that have had guides replaced once before by someone else.

Always use the bronze-silicon guides and never cast iron, they don't work in a VW head. I just ordered in a couple of hundred guides in all sizes, if you need any let me know.
Mark

See. He does it for a living and I watch people do it for a living. I have done a lot of them in the past (with minimal tools) Listen to Mark.


B

Mark has rapidly become my engine parts supplier. In all correspondence with him he really seems to know what he is talking about.
As for the heating, in my experience with any kind of press/shrink fit, I have found heating to some degree only helps in dis and re-assembly. I might be wrong with these heads.
I will try Marks coring, remove the top and try taking them out the bottom after leaving them in a electrode oven (200*F) for an hour or 2.
Mark, what do you use to remove the top of the guide? I was thinking a counter boring bit or a step drill.

Thanks for the kind words Doug.

You have to mill the guide tops off flat. If you core the guide and are real careful you may be able to take the top off with a drill bit. You don't want to damage the boss.
I do use a step drill bit for coring the guide.

I have a simple tool for doing this and it also can be set to cut the boss for dual springs.

When cored properly you don't have to heat the head.

Good morning everybloody. Here's some info that might help.

didn't have coffee yet

got him!

i'm going to leave the post up here cause it might actually help the topic.

Andy

That explains a few things...

Welcome to the club RFL.
Tx for the info, your signature is right, book is good.
Looks like Mark must have read this somewhere too.

Tx all
Doug

What about trimming or Tapering the protruding end of the guide? Does this aid flow to any significant degree?

Ack...Alfred! Good Info tho... Not to mention his D-Jet page rules...

Rich,

a lot of people who flow heads cut the guide off completely after it exits the head into the flow path. The theory is: the valve doesnt lose much support by cutting off that small amount that is exposed (race heads)

Mark may have more info.


B

It might add a small amount of flow on a short life race head, but I like all the support I can get, so I'll never cut them off. I do taper the guides a bit on high-end heads.

Good article Alfred, I'm swamped with work so I only scanned it, but it sounds about right. What book is that from? I think I seen it before, a high school text perhaps?

Everything I know is one half reading/research and the other half hands on experience.