TDC & distributor installation

[hands_aus]

quote:Originally posted by merrill

so,
here is more info on keys and another photo

Camshaft Woodruff Key
An offset to the right(in the direction of rotation) results in an earlier valve opening, while an offset to the left results in a later valve opening.      

5 Degrees:  1.3mm = 10 deg. at crank
4 Degrees: 1.1mm = 8 deg. at crank
3 Degrees: 0.9mm = 6.5deg. at crank
2 Degrees: 0.7mm = 4 deg. at crank

if needed one can also remove a link and add a key to correct timing


Download Attachment: offset.jpg
14.14 KB

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

Matt,
Great pics and info,
Thanks

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[merrill]

so,
here are the current part numbers for the offset keys

621 991 04 67  2 deg at cam 4 at crank
621 991 02 67  3 deg at cam 6.5 at crank
621 991 01 67  4 deg at cam 8 at crank
621 991 00 67  5 deg at cam 10 at crank


Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Benz Dr.]

The valve timing can only be set with a dial gage and a degree wheel on the cam shaft.
 The correct setting for checking valve to piston clearance is 5 degrees ATDC on number 1 piston. You need to use a dial gauge and push down on the intake valve until it hits the piston. You need about 1 mm of clearance.
The piston actually slows down and stops when it reaches either end of it's travel as the crank goes over center. Since the piston stops but the cam shaft keeps moving the valve will get very close to the piston at 5 degrees ATDC until it starts to move down in the cylinder.

The off set key moves the cam shaft and not the gear so the guy at Metrics is being straight with you about that. If there is no off set key and the marks are out slightly it's not the end of the world. Unless you do the valve timing test according to the BBB it's all suposition anyway.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[ja17]

Hello Matt and Dan,

I see the point Dan and the fellow at Metric are making and I correct my previous post.  As noted, the off keys will get the actual cam timing closer but will make the alignment of the cam timing marks off even more! Does not make sense, but true. Do not mistakingly put the off-set key in opposite. If you do the alingment marks will be closer but the actual cam timing will be off even more.!

I guess if you use the off set keys, be prepared to use a dial indicater to do the valve timing.

There is always something to learn here by this group, even for the experienced!

Joe Alexander
Blacklick, Ohio

[Benz Dr.]

One more thing:
The woodruff key carries no lateral tourque and so it should never break off. When you tighten the screw it presses the gear against the cam shaft and prevents it from turning. The woodruff key is there to set the relationship between the cam gear and the cam shaft with the intent of  keeping the cam shaft and crank shaft in time with each other . The woodruff keys on the distributor drive and on the crank shaft act in a similar fashion.
Only the cam shaft is provided with an off set key to make adjustments for machining and other variations. The trick is to always use a new crank shaft gear if you have the bottom end apart. The crank gear has to run the cam shaft, oil pump, distributor, injection pump and idler gears. It takes a pounding and wears out twice as fast as the cam gear. If the teeth on the cam gear are pointed you can bet the crank gear is badly worn. Best bet is to replace all the gears during rebuild.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[merrill]

so, I finally checked the valve timing today.
followed the bbb in structions and found the timing to be off 2 maybe 3 deg atdc at the crank.  so the cam timing is probably off 1.5 to 2 deg off

just for fun I checked the valve clearence and it was dead on so for now I will leave the current woodruff key in .

once I get the motor running,  I will check the timing again.

matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

Dan,
your reply made me double check the bbb and the timing correction.

per the bbb if the crank timing is off, the cam timing is off half that amount.

so 4 deg at the crank would be 2 deg at the cam.

matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[glennard]

Blacklick topic---JA et al.   Sounds like there should be a 'Engine Fundamentals 101' at Blacklick.  How cranks, pistons, cams, distrib

[glennard]

quote:Originally posted by glennard

Blacklick topic---JA et al.   Sounds like there should be a 'Engine Fundamentals 101' at Blacklick.  How cranks, pistons, cams, distrib

utor, FI pump, oil pump, fan, plugs, etc, etc,  all work in sync.

[ja17]

Hello Glenn,

Yes we will have a "take apart engine" on a stand for the tech session so we can disect it and reveal these mysteries!

Joe Alexander
Blacklick, Ohio