Use of Go-No-Go Gauge for Valve Shim Replacement - PeachParts Mercedes-Benz Forum

mbboy · #1 01-12-2009, 09:01 AM

The MB manual for the 380sl, which has the 116.690 engine, explains rather briefly that the relationship between the engine's valves and cams can be adjusted by:

1) Placing a movable pin of a specially designed go-no-go gauge over the rocker at the lifter when the corresponding cam lobe is up,

2) Determining how far a line in the center of a 1.1mm notch on that pin deviates up or down from a line determined by the measuring edge on the gauge, and

3) Replacing the existing shim with a thicker or thinner one, thereby bringing the first line closer to, and ideally in line with, the second.

My questions are:

1) How far off from the gauge's measuring edge should the movable line be before a shim change is warranted?

2) Can the thickness of the replacement shim be calculated by measuring the distance between the gauge's measuring edge and the pin's movable line? For instance, if the movable line is, say, .25mm above the measuring edge, does that mean the the replacement shim should be .25mm thinner than the existing one?

3) Can a too thick shim be reliably ground down to the correct thickness, or should new ones always be used?

3) What is the thickness of the original shims on the 116?

Thanks very much in advance for any answers anyone can give me to to these questions , and for any additional info on the best way to measure and replace valve shims.

Strife · #2 01-12-2009, 06:33 PM

1. I THINK that it was 5.1 mm.
2. In my opinion, these are generally OK as they are unless:
a. You had the head shaved (not recommended)
b. Valve/head work has deepened the valve pocket a little, thus raising the valve a little
c. You changed the hydraulic compensator and it didn't thread exactly like the old one
3. There is an oil drain groove in it, so machining would NOT be good, it is also probably case-hardened.

Pooka · #3 01-12-2009, 09:49 PM

You would absoulty NEVER get the precision you need by grinding one of these down. You can buy a kit of shims that has different sizes in it, though.

I am 'supposing' on the shim kit being for sale because I know older Volvos use shims for this and they sell such a kit. Most import shops have these shims in stock, so you might just have this job done.

Pooka

mbboy · #4 01-13-2009, 06:08 AM

Quote:

Originally Posted by Strife

1. I THINK that it was 5.1 mm.
2. In my opinion, these are generally OK as they are unless:
a. You had the head shaved (not recommended)
b. Valve/head work has deepened the valve pocket a little, thus raising the valve a little
c. You changed the hydraulic compensator and it didn't thread exactly like the old one
3. There is an oil drain groove in it, so machining would NOT be good, it is also probably case-hardened.

Thanks, Strife. I guess I should have mentioned that the the valves were were recently redone, the heads milled, and the rockers put back in different positions, for reasons I explained in a previous thread. Based on info I've gathered so far from a number of very experienced Indy's, MB techs, and particularly someone who's been working exclusively on cams for over 30 yrs, I've concluded that changing rocker positions is not nearly the problem some people have made it out to be.

In addition, I've been led to believe that changing the shims to balance out any differences in the relationships between the rockers and cam lobes will reduce the possibility of valve clatter. So, that's why I started this thread. However, I'm still not quite sure how to calculate the thicknesses of the shims I'll need?

mbboy · #5 01-13-2009, 06:18 AM

Quote:

Originally Posted by Pooka

You would absoulty NEVER get the precision you need by grinding one of these down. You can buy a kit of shims that has different sizes in it, though.

I am 'supposing' on the shim kit being for sale because I know older Volvos use shims for this and they sell such a kit. Most import shops have these shims in stock, so you might just have this job done.

Pooka

I wish that MB or some aftermarket parts manufacturer did make such a kit, but I haven't seen one. And if anyone here has extra shims they'd like to sell, I'd be interested in hearing from him.

Since I already have the engine out of the car, and have redone just about everything such an engine needs at about 200k, I'd also prefer to do the shimming myself. But thanks anyway for the advice.

mbdoc · #6 01-13-2009, 08:13 AM

To start with, MB used several sizes to adjust valves from factory. MOST were around 4.8-5.5mm.

You do need an assortment of shims! So order at least 4 of each size below 4.8mm, of course measure all of the ones you have to start with.
Then the fun begins.

mbboy · #7 01-15-2009, 09:56 AM

Quote:

Originally Posted by M.B.DOC

To start with, MB used several sizes to adjust valves from factory. MOST were around 4.8-5.5mm.

You do need an assortment of shims! So order at least 4 of each size below 4.8mm, of course measure all of the ones you have to start with.
Then the fun begins.

Thanks, Doc. I don't know if I lucked out -- or what -- but when I tested the rockers yesterday, all of them were perfectly centered on the gauge's measuring line.So, hopefully, I won't have to re-shim them after all.

hey_allen · #8 01-15-2009, 01:42 PM

I have to ask, is there any way to measure this without coughing up for the special tool?

Dial indicator from a known height?

It just irritates me when I end up having to buy single purpose tools, so I work to either find a way to do the task with standard ones, or to fabricate my own.

Thanks for any ideas or suggestions.

rs899 · #9 07-12-2011, 12:17 PM

Reviving an old thread....

Doesn't look like "Hey Allen" got an answer, so I will ask it again.

Is there any workaround or is there a DIY hydraulic compensator measuring tool?

I need to gird my loins for this sort of activity, and since the blasted shims are $15 each, I don't feel the need to spend $70 for what appears to be a simple ( if well made) tool that probably doesn't need to be THAT precise (since the compensator , well,.... compensates).

Stretch · #10 07-12-2011, 01:00 PM

Quote:

Originally Posted by rs899

Reviving an old thread....

Doesn't look like "Hey Allen" got an answer, so I will ask it again.

Is there any workaround or is there a DIY hydraulic compensator measuring tool?

I need to gird my loins for this sort of activity, and since the blasted shims are $15 each, I don't feel the need to spend $70 for what appears to be a simple ( if well made) tool that probably doesn't need to be THAT precise (since the compensator , well,.... compensates).

I've never seen the engine - but if you post or send me a picture / schematic I'll see what I can do.

rs899 · #11 07-12-2011, 02:32 PM

http://zdmak.com/wbstore/main.asp?action=PROD&PROD=M0024&CTMP=1

Here it is.

Stretch · #12 07-12-2011, 02:54 PM

Quote:

Originally Posted by rs899

http://zdmak.com/wbstore/main.asp?action=PROD&PROD=M0024&CTMP=1

Here it is.

PM sent

Stretch · #13 07-13-2011, 03:42 AM

Here's a picture of the set up - hope it helps

rs899 · #14 07-13-2011, 06:49 AM

^^basically just a very fancy single purpose depth gauge. In use on the M116/M117 the rocker arm is removed first, before this is used.

Anyone have one that could share the critical dimensions?

mbdoc · #15 07-13-2011, 08:24 AM

In the beginning (1976) we didn't have that special tool!

In fact the 1976 model year book had a nicely layed out tutorial on how to set
the lifter height with a dial indicator, was somewhat a pain!

I'll see if I can get a scanned version of that procedure.