valve guide removal and installation tool

[CJHenderson]

Any recommendation for a valve guide removal and installation tool and what size do I need? Getting ready to start working on the head after the holidays.

[Shvegel]

 Granted it isn’t rocket science but are you sure you don’t want to leave it to a good machine shop. Drop off head, valves, guides. Get back done.  I tend to like to rely on the experience of people that do a hundred a week to go, “That guide feels a little loose to me. I need to check it out further.”

[CJHenderson]

I prefer to do this myself.

[ja17]

CJHenderson, you have a lot of research ahead of you if you wish to do this yourself. I agree with Pat, and I also send my heads out to an experienced machine shop. I supply the machine shop with all the factory specifications and any special tools they need to use.  If you do wish to do it yourself, there are lots of special tools needed for the job. Mercedes published "special tool catalogs" over the years. Many tools are listed in these as well as in the "BBB" shop manuals. The MB part numbers are furnished so special tools can be ordered. Finding step by step instructions will be hard to find since most dealerships did not even do all the machine work when re-conditioning cylinder heads. Use the "Technical Data Booklets" and the BBBs various versions for specifications on wear limits and machining tolerances.
If your head is not flat, you will need to have it machined first. For valve guides, there is a special MB tool (go/no go gauge) to measure inside diameter wear (one tool for intake another tool for exhaust). Another special tool is used to drive the valve guide out of the head. Another special MB tool is used to install the valve guide (one for intake and one for exhaust). Before installing guides the holes and the outside diameters of the guides should be precisely measured. If the valve guide hole in the head is too large then an oversize guide must be selected, then hole in the head must be sized accordingly with another special MB tool (broach). Once the guide is installed in the head the inside diameter of the guide must be sized with a special tool (reamer) so as to fit your new valves. Sometimes the heads are warmed or the new guides are chilled before installing them in the heads. Once the new valve guides are installed, the real work begins! Valve seats must be machined using special pilot tools and valve seat grinding equipment. On rare occasions a valve seat may need to be replaced. You will at least know how to examine these circumstances. These days it makes sense to replace all the valves with new, since the price of new valves is not significant. If you do not replace all the valves with new, then you will need an expensive valve grinding machine to reface the valves. Specifications for valve seat angles and widths are given in the factory documentation along with permissible wear of valve stems and minimum thicknesses of valve edges after machining. Correct width of valve  contact at the valve seat must also be achieved. Etc. Etc.
An experienced automobile machinist, besides having the tools, also has the experience to know how to identify problems or issues and will also have the "feel" of the work and know what typical problems to look for.
Review some internet videos and read some general engine rebuilding manuals to get some general knowledge on reconditioning cylinder heads first.

[CJHenderson]

Well so much for that train of thought. After your post then I can see I'm biting off more then I can chew. I'll just have to find a machine shop to rework the head. Thanks to both Shvegal and ja17 for the advice.

[MikeSimon]

Small question about the valves: Depending on the condition, would it be sufficient to lap the valves instead of replacing them? If you replace the valves, you should replace the valve seats. If you try to avoid this, would lapping be good enough?

[ja17]

Lapping the valve seats is usually done after the valves are ground (re-faced). Although lapping can restore the valve to seal properly, grinding of the valves  is usually required first to achieve the correct  angles, widths of seat and flatness  at the valve faces. Valve seats will usually last several cycles of head re-conditioning unless damaged. The valve seats must be resurfaced also so that the seat angles and width of seat are correct. After the valves and seats are ground to specs, lapping is the final step in making a perfect seal between the valve and seat. A grinding compound is used to do this final stage where the reconditioned valve is ground and fitted to it's reconditioned seat. Just lapping old valves and not resurfacing them will cause the seat surface to become too wide and will not restore the correct three angles of the valve or its seat. Valve stem wear is also a critical factor when doing a valve job. They all wear and there is a critical wear-limit specification, provided by the factory, which must be adhered to, when using the old valves. With modern automated manufacturing processes, new valves have actually become less expensive over the years and now can be sourced inexpensively. New valves come with no stem wear and the valve faces are already ground to correct angles and thicknesses. Most feel a complete set of new valves is a good investment these days. Machine shop costs are reduced also, since labor to re-condition the old valves is avoided. Valve seats must still be reconditioned with new valves. Finding a machine shop with experience on Mercedes aluminum heads is best if you can. The skilled workers that "fix and recondition" engines and cylinder heads are disappearing fast these days. I bought all the special equipment and tools to recondition cylinder heads last year, figuring I might have to do all the work myself eventually. Finding a machine shop to correctly do the work these days is becoming increasingly more difficult.

[CJHenderson]

Since this motor has 102,000 miles I wonder if the valves are that bad off, they have a lot of carbon. The head was cooked because who owned it never ran antifreeze so that means the blackened face saw several boil overs. I'm really trying to keep from getting a refurbished engine from California.

[MikeSimon]

I always thought - and I have done that many times on small engines - that lapping existing valves on their seats will "restore" the seat to an extend. It will remove any deposits and imperfection and thus recondition both the seat surface on the valve as well as that on the valve seat. This is a process you should only do by hand with the proper tools and a lapping paste

[ja17]

At over 100,000 miles check the exhaust valve stems with a micrometer for wear. Worn valve stems will decrease the life of the valve guides, valve seals and valve faces as excessive valve movement causes wear and oil leakage past guides. Even if new valve guides and seals are installed,
 worn valve stems will increase the rate of wear. Precise measurements and adherence to factory wear limits will take the guesswork out of the job.