easy way to remove valve guides

[Dave H]

If you have the cylinder head on a bench proceed to tap out the inside of the guides from above, only go 3/4" deep. Use a 10mm tap for the inlet and 12mm for exhaust....screw in a bolt, spin the head over and hey presto ,you have something to knock against from the other side.
Including tapping it took 2 hours ,start to finish, they were all out !

Just got to come up with a way of refitting the new guides ....my plan ,up to now ,is to warm the cylinder head on the lounge radiator and cool the guides in the freezer.
Anybody know if this is likeley to work ?
It sounds like it should do the job but these little fellas are tight.

[twistedtree]

I've always left the removal and installation of guides to my machine shop, but wouldn't one preferably use a press for the job?

[Benz Dr.]

You can heat the head up to about 200 degrees and cool the valve guides. If they're sized properly they will push in without too much effort. You should never force them into the head because the guide will distort.
Properly installed, the new valve will have a small amount of play ( .0005'' ) and will easily move in the guide. If the valve stem is tight, the guide will need to be honed out a small amount.

[w113dude]

I like it, very cleaver

[Dave H]

The removed guides were all standard ,none had come loose nor had there respective seals come off.The old guides were however starting to go oval .
I cleaned up the old valves last night and tried to fit them into the new guides .
I noticed they would not go at first untill i slightly dressed up the very end of the valve stem with a smooth file.They appear ever so slightly "mushroomed" on the ends through contact with the rocker.Nothing you would notice with a naked eye but mushroomed all the same which at first made me think i had ordered the wrong guides.
Anyway a little tickle on the end with a file and they all fitted niceley into the guides.
I shall be lapping in the valves and refitting the guides at the weekend, the head i will gradually warm untill the cooled guides just pop in .
Will keep you all informed and will go sensible with the warming up so as not to distort anything.Hopefully the lounge radiator will do the trick otherwise im gonna scare it with the stove....! dont you just love pottering about in the shed .
Will take plenty of pictures now i have the hang of posting them.

[ja17]

Lapping in the valves is normally the last step. Most valve seats need to be slightly "cut" or ground to be trued-up after new guide installation. Be careful, just lapping the valves in without grinding or cutting first, as this may cause  the valve seat area to become too wide. Look for specs in the MB BBB for all this information.

[Benz Dr.]

Lapping in the valves is normally the last step. Most valve seats need to be slightly "cut" or ground to be trued-up after new guide installation. Be careful, just lapping the valves in without grinding or cutting first, as this may cause  the valve seat area to become too wide. Look for specs in the MB BBB for all this information.

And that's why I take it to a machine shop. The valve seat will not line up with the valve after you install the new valve or guide. My machine shop uses a cutter that cuts all of the seat at one time so they all come out at the right angles and the same exact size. You can't get that by grinding. I'm pretty sure they don't need to lap the valve and seat in - their equipment is that acurate.
The magic is all in the valve seats and how well everything flows across the faces.

You also have to look very carefully at valve rocker geomerty. If it's not right you can wipe out a new set of valve giudes in a matter of a few miles.

[Dave H]

I agree with you both...lapping alone would be old school, it would still have a better seal than before but would not last as long as a proper cut seat.
I intend to find a good machinist to cut (not grind) the seats.
Valve rocker geometry makes a lot of sense too..i can see how this could be upset once you get towards the limits of the ball adjusters .
Thanks as always for the good advice. 

[Dave H]

Does anybody have the valve seat specs from the MB BBB ?

[Benz Dr.]

I agree with you both...lapping alone would be old school, it would still have a better seal than before but would not last as long as a proper cut seat.
I intend to find a good machinist to cut (not grind) the seats.
Valve rocker geometry makes a lot of sense too..i can see how this could be upset once you get towards the limits of the ball adjusters .
Thanks as always for the good advice. 

Yes, rocker geomerty is very important. As you grind or mill the valve seats the valve stem will move higher and you will need to adjust the ball stud down. At some point you will run out of adjusting room. With worn valve guides this won't be too much of a problem but with fresh inserts they can be damaged very quickly.

I like to see some of the thread showing on the ball stud adjuster. If you can't see any thread showing it's already pretty low. I use cam bearing shims to raise the cam shaft about .08 mm which is more than enough to correct the rocker geometry.
If you leave this as is, the rocker will tend to push the valve stem sideways and take out the valve guide/s. THe valve guide will have little end to end play but from side to side it will be quite loose upon inspection. The engine will smoke and never stop until you change the guides. 

[w113dude]

if the valves are going to be replaced I understand, why would the seating matter if only the valve guides are being changed. is there a correlation?

[Benz Dr.]

if the valves are going to be replaced I understand, why would the seating matter if only the valve guides are being changed. is there a correlation?

Yes. The installed parts wear into each other so when you change something the new parts won't fit the sme way as the old ones did.

[Dave H]

So im on the look out for a competant machine shop to do a proper 3 angle valve cut....
Shame is ive just had the head soda blasted so they better wear gloves !
What benefits have people had from matching and polishing the head ports, i will get this done at the same time and also have the manifolds sent for ceramic coating. i will watch out that i dont get close to running out of adjustment on the ball studs...couple of threads sounds about right.

[Benz Dr.]

So im on the look out for a competant machine shop to do a proper 3 angle valve cut....
Shame is ive just had the head soda blasted so they better wear gloves !
What benefits have people had from matching and polishing the head ports, i will get this done at the same time and also have the manifolds sent for ceramic coating. i will watch out that i dont get close to running out of adjustment on the ball studs...couple of threads sounds about right.

Have them install the valve guides first so they can get the seats centered.

 I did all of my ports and matched everythingh to the manifold gasket. This is a bit of a black art and a flow benmch is the only way to know if you're going in the right direction.
 I can stay that a stock head flows better than you would expect. I had one flow tested; dirty and not cleaned up, and the guy was impressed. So based on that you might be able to make yours better.

I know of a place ( who shall remain unamed ) that says they can port and polish a stock 190SL head that will give you 15 more HP!

 I know that's BS - 5 HP would be a lot. 

[w113dude]

Just got to come up with a way of refitting the new guides ....my plan ,up to now ,is to warm the cylinder head on the lounge radiator and cool the guides in the freezer.
Anybody know if this is likeley to work ?

I use a large BBQ works great!

[Dave H]

5HP would be enough...i just want to give it the best chance of a smooth idle as possible.
Apart from the head job the motor is getting amongst other things all new sprockets,chain ,tensioner,wear plates,oil pump and main bearing shells and seals.
The injectors are new and ive just had the pump rebuilt so i hope it will run like a bobbin for many years when complete.
Thanks for all the great advice...

[Dave H]

barbeque....!.now thats really gonna mucky me head but like your style

[jacovdw]

...As you grind or mill the valve seats the valve stem will move higher and you will need to adjust the ball stud down. At some point you will run out of adjusting room...
... If you can't see any thread showing it's already pretty low. I use cam bearing shims to raise the cam shaft about .08 mm which is more than enough to correct the rocker geometry... 

Dan,

What about the different sized thrust pieces used on the valve spring retainers also used for adjusting the geometry?

There are 3 different sizes available with the standard being 4.5mm and the two repair sizes of 3.5 and 2.5mm respectively.

[Benz Dr.]

I'm aware of the thinner lash caps but I prefer to use cam bearing shims. With new gears you can run into problems with the chain becoming rather tight but that's not a common problem. I use anywhere from .015'' to .030" shim thickness depending on what I need.

By the time you get down to the point where you need smaller lash caps you're already at a point where you really need to get the cam higher. The smaller 3.5 mm lash cap will give you about .040'' more clearance at the end of the valve stem which would be egual to what I'm using with .030'' cam shims.
NOTE: cam shms come in different thickness but I use .015'' which is as thick as you can get. 

[tel76]

Dan,
Where do you get your ready made shims from?

[Dave H]

sorry wrong picture,

[Benz Dr.]

You won't want to get your head too hot or the valve seats could come loose. You could get some marking pencils that are heat sensitive and will melt at the desired amount.

Cam shims?  That's a company secret.

[ja17]

Hello tel76,

Ready made shims are available from your local MB dealer, part distributor or Classic Center, in various  different thicknesses. If you use very thin shims the rocker arm can become to close to the top valve spring retainer and actually hit the retainer before contacting the valve shim.  Not a good situation. You also get a mysterious valve train tapping when this occurs. Be on the look out for this when using thinner shims. A little grinder work in the non critical part of the rocker arm (where it crosses over the valve retainer) makes everything happy again!

[Benz Dr.]

I say lash caps and you say shims. I think these are the same parts.

The cam shims are something totally different.
Didn't want to get anyone confused.

[wbain]

Before any work is done, measure the head for warp. Warped heads can be flattened, to a point, by bolting the head to a flat plate and heating it. Machine shops can do this.

The easiest way to remove and replace the guides is by using liquid CO2. The guides will drop out and then in.

Valves need to be faces on a valve grinder. Seats need to be ground in place, I'll post some pictures soon.

If a seat needs to be replaced, heat the head in an oven, not your kitchen oven but an old one that used to be in your kitchen.

1st pic, facing a valve.
2nd pic, con rod comparison, M180 rod, Porsche 944 rod, generic US V-8 rod, dragster rod
3rd pic, M180 block being bored for next piston oversize
4th pic, honing the cylinders.

I'll find some more pics. soon.

I hope this helps.