Anyone ever replace a valve guide?

[gsJack]

Well, I finally tore apart my engine today to check the damage from the recent valve crash caused by a sticking tappet:

http://www.gstwins.com/forum/viewtopic.php?t=15886

The head of the #2 cyl exhaust valve was broken off.  There was a small indent in the piston crown that looks like it was made by the valve and a bit of a mark in the combustion chamber.  Not concerned about the head marking and the piston looks like it will be OK.

Big problem is that the end of the valve guide was broken off in a jagged irregular manner.  Looks like it really needs to be replaced and that is probably a shop job?  New guides are all oversize according to Chilton and the hole in the head must be reamed to fit the new guide and after it is pressed in the inside bore has to be reamed to fit the valve.  There is a special tool to drive the old guide out and the new guide in.  Wondering if anyone here has ever tried this themselves?

[GRU]

i did it but not on a gs head..mostly v8 cyl steal heads

a shop can do that for you but i just hope they don't overcharge you...it's not a big deal to do but i can imagine some shops like to charge way too much

[The Buddha]

OK guides are interference fit ... meaning ... they heat the heat to like 500 or whatever and knock the guide out and knock the new guide in. You're in luck ... ok relatively speaking ... cos Kibblewhite makes GS valves and springs ans the whole kit and kaboodle. www.blackdiamondvalves.com. Just talked to them for my savage ... no dice ... But GS ... easy.
Your problem might be that if you heat the head to the 500 degrees ... all guides will get loose enough to get knocked out of place ... so might need all new guides ... and I'd put new valves and springs and seats ... Oh yea you'd need seats too most likely cos they also will get loose ... On my savage ... the intakes looked good ... but were slightly bent, exhausts were toast, seats are ovalled out as well ... and I have 2 deep impact craters right by the seat ... I am having to weld in and smooth out the craters ... and They said they'd weld the head bit by bit ... slowly so it wont heat too much and warp or ruin the seats ... Then I cut the seats true, and reuse the springs and keepers and collars etc and new valves from  :x  :x  suzuki or vesrah ... I tried desparately to get new everything of better quality from Kibblewhite ... nothing ... Not even close ... For a GS I'd buy the whole lot from Kibble white, have my local machine shop knock the guides and seats out, weld and smooth the head (cant have a dimple or a zit there ... it will develop a hot spot and detonate there ... ) and fit the entire lot of new parts in that head ...
Cool.
Srinath.

[Bob Broussard]

You can grind away the part of the guide in the port. Racers do it all the time when porting heads. They either grind the guide to a fine taper to blend into the valve stem. Or you can grind it completely off if necessary.
Replacing the guide requires doing a valve job so everything lines up and the valve seats properly.

[Blueknyt]

heating the head is easy,  First completely disassemble everything in the head, make sure all gaskets, seals, moveing parts, and everything like that are removed, then CLEAN IT, so you can almost eat off it. you can do one of 2 ways,Oven or BBQ grill. Put the new guide in freezer,  preheat your oven to 400-500ish, put it in and cook, checking every 10 mins by putting a punch hammer to it.  Have someone with leather gloves or ovenmits hold the head still for you ontop of a cookie sheet on floor infront of oven, its best to do it right out of the heat as the head will cool fast. pull the new guide out of freezer and have it next to you when you pull the head from the oven. Once the old one pops out, love tap the new one in place, make sure it seats all the way in.  ive also seen Liners removed from cyl this way and press on bearings installed on cranks.

[mp183]

heating the head is easy,  .....preheat your oven to 400-500ish, put it in and cook, checking every 10 mins by putting a punch hammer to it.  

Don't forget that you have to wear your sneakers to do this.
You are going to have run like hell when your wife sees what
you did to the oven.  :lol:  :lol:

[gsJack]

Srinath, my not always trusty Chiltons suggests heating the head to 200-300F and putting the new guide in the freezer to accomplish the press in.  Would not be concerned about those temps since they are not that uncommon in cyl heads.  I too would be a bit concerned about 500F.  Will check out that parts source you mentioned.

All 3 of the other valve tappets are a nice fit in the head, but the one for the broken valve is still compressed a bit and very tight.  I thought I'd put the head in the oven today and and heat to about 200F to see if I can't lift the tappet out like I did the others.  It always loosened after the engine began to heat a bit.  

Bob, thank you.  Why didn't I think of that.  :lol:  I'll get a grind wheel for the drill motor and give it a try.  Did a lot of that stuff a half century ago messing with car engines.  A couple guys in the garage I worked in thru high school and college raced stock cars at Soldiers Field (Chicago) and I always wanted to join them.  By the time I was 21, I had a family instead.

Soon as I borrow my sons valve spring compressor, I'll pull the intake valve from that cylinder and lap it in to make sure it's straight before re-using it.  Looks now like the exhaust valve hit the piston and not the intake valve.  Sure glad it was at cranking speed.  

Thanks for the helpfull input GRU and Blueknyt.  I'll probably wait till the wife goes out later today to put the head in the oven, mp183.  Been married 53 years and don't want to spoil it now.   :lol:  :lol:  :lol:

[The Buddha]

200 degrees ... Man that's nothing ... the guys said 400 I thought at the engine shop. In any case ... Use the good stuff and make a entirely new head ... I wish I could but nothing is available for my head ...
Cool.
Srinath.