Hello mistertj.
I'm the one who has been discussing the 230SL WRD with Wallace Wheeler. When I first took my WRD apart, I measured the length of the piston and rod assembly as it was before I decided to take it apart. I'm not sure there is a given factory length for all WRD rods, but mine was nearly the same as yours, albeit wrong because mine, which looks exactly like yours would shut off the air at 50 degrees C. Mine measured 66.36 mm from the tip of the rod to the tip of the small black screw, where yours is 66.55 mm. I finally got it to shut off at 80 degrees C with an adjusted length of 65.20 mm, but that included screwing the small black screw all the way in and correcting the installation of the brass colored hex head dowel on the side of the bore, the problems of which I have been discussing with Wallace Wheeler in the other WRD thread. The small black screw determined the piston distance from the screw hex and the overall rod length, but the brass colored hex head dowel was restricting the piston and rod travel and delaying contact with the thermostat pin until late in the warmup period.
If you have been following my and Wallace's discussion, you know that I only have one oval shim where you apparently have two that I can see in your photo.
Thank you for your photo. It has taught me that more than one oval shim means that the oval shims are to adjust the engagement of the end of the rod with the fuel lever inside the pump and controls the amount of fuel to be mixed with the air flowing through the WRD. According to Joe Alexander (JA17), the bottom of the piston is supposed to shut off the air port when the coolant temperature reaches 80 degrees C, not 50 degrees C like mine was originally. Once that is correctly adjusted by adjusting the little black hex screw on the piston, if the mixture it too lean or too rich, the air fuel ratio during warmup can be further adjusted by adding or removing oval shims between the WRD and the Pump Body. Adding oval shims = less fuel lever contact and more fuel during warmup), Removing oval shims = more fuel lever contact and less fuel during warmup).
Since air flow quantity is a function of coolant temperature controlled by the thermostat moving the piston relative to the air port (lower edge of the piston position vs the bottom edge of the air port in the body) and at the same time, how much the end of the rod pushes on the fuel lever in the pump, the ratio of air to fuel should be almost constant but the quantity of both should be decreasing as the coolant temperature approaches 80 degrees C where the WRD fuel and WRD air both shut off.
I have determined that my rod tip is worn flat by contact with the fuel lever in the pump so to get back to the original engagement with the fuel lever I need to add rod length (not possible), so I will remove housing length (by removing an oval shim - the only one still installed).
So you see, it is normal on the 230SL to have both the little black screw to make the air shut off at 80 degrees C, and the oval shims in a quantity correct to make the correct amount of engagement of the rod tip to the fuel lever in the pump. If both are correct, then the air fuel ratio as well as the quantity of both fuel and air will be correct during warmup, which ends at 80 degrees C.
I'm sorry for the sermon. but I felt that almost all of the Pagoda technical discussions in the forum relate to the later cars whose engine characteristics are very similar but critically different than the 230SL. The Technical Manual is a great help but there were too many things I could not learn relating to my 230SL. These discussions with you and Wallace have provided little tidbits of information that solve a lot of my problems. Until your photo, I did not know that the 230SL had more than one oval shim under the WRD, since mine has only one. Until I took mine apart, I did not know that the brass colored hex head dowel could be improperly installed, completely screwing up the warmup function. I also did not know that the tip of the rod could be shortened by years of contact with the fuel lever inside the pump requiring oval shim removal to increase rod penetration into the pump.
At some point, these things and probably many more eccentricities of the 230SL engines should be entered into the Technical Manual for 230SLs only.
Let's keep up the 230SL communications.
Tom Kizer
