Camshaft sprocket woodruff key?

This is a question which I posted on another VW forum and did not get a final answer. Maybe here I will:

The 4 cylinder VW diesel engine camshaft sprocket according to my Haynes manual may or may not need a woodruff key. My camshaft sprocket end has a keyway and I assumed that a woodruff key was needed. I heard however from another forum that a key should not be there. My question is this: why would VW engineers cut a keyway in the tapered end of the camshaft is a woodruff key was not intended.

Thanks.

Haybayian.

In order to set the valve timing you actually move the sprocket on the camshaft, so you CANNOT have a woodruff key there. This timing must be adjusted whenever the timing belt is replaced.

The key slot may be left over from when the cam was an unground blank and didn't know it was a diesel cam yet. (The cam blank might get ground for an engine that uses a woodruff ket or not, but perhaps all blanks get the slot early in the manufacturing process regardless of ultimate use.)

HTH

Bill

The woodruff is not used for diesels, as 40 x 40 pointed out. The slot at the opposite end of the camshaft is one of three timing marks (pin in injection pump, TDC markand the slot in camshaft with both #1 lobes up) used to set the engine static timing.

The Haynes manual is not specific enough. Get a Bentley.

Also, when retorquing the camshaft sprocket bolt, I use 45 ft. lbs (60Nm) instead of 35 ft lbs (45Nm). I've seen several sprockets slip when using the lower torque number.

Stick with the 33 ft-lbs, the only way that sprocket is going to move is if the guy torqueing it down used a torque wrench that was out of calibration.

Overtorqueing is just asking for trouble when it comes time to remove the pulley. In the 30+ years that this system has been used not a single documented failure has occured when the PROPER torque has been applied.

Increasing the torque to compensate for tools in poor condition is flat out bad advice.

I use either a digital torque wrench or one of my mechanical torque wrenches that are calibrated annually. I reset them to 0 after every use to avoid spring tension errors, thus far I have always gotten them back with no calibration adjustments required. When people leave a torque wrench set to a torque setting for any extended period of time, the resulting error in torque values can last up to 2-3 weeks resulting in unknown values being applied when torqueing a fastner.

DB

Franko6 said:

The woodruff is not used for diesels, as 40 x 40 pointed out. The slot at the opposite end of the camshaft is one of three timing marks (pin in injection pump, TDC markand the slot in camshaft with both #1 lobes up) used to set the engine static timing.

The Haynes manual is not specific enough. Get a Bentley.

Also, when retorquing the camshaft sprocket bolt, I use 45 ft. lbs (60Nm) instead of 35 ft lbs (45Nm). I've seen several sprockets slip when using the lower torque number.

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Thanks TDI friends,
I will take your advice.
I guess I will never know why VW bothered to cut a keyway in this camshaft blanks.
Haybayian

haybayian said:

(snip) I guess I will never know why VW bothered to cut a keyway in this camshaft blanks. Haybayian

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__. Only a WAIG, but there has to be some way to index the "central position" of the cam when the profiles are cut; otherwise, there would be no way to assure the correct relative positions of the different lobes. I'm also going to guess that there may be some moving between machines in the manufacturing process (again, only a guess, but I'd guess rough machining then heat treating and then final grinding). I'm guessing that gassers use the keyway for indexing the manufacturing processes of the cam - since they have to have the keyway for installation in the vehicle - and diesel cams have the keyway cut for the same production indexing because that's how the production machinery is made.

__. I went over to the machine shop at Land Rover and spent an half an hour or so watching con rods being made but I didn't get that familiar with the process for cams.

mrGutWrench said:

__. Only a WAIG, but there has to be some way to index the "central position" of the cam when the profiles are cut; otherwise, there would be no way to assure the correct relative positions of the different lobes. I'm also going to guess that there may be some moving between machines in the manufacturing process (again, only a guess, but I'd guess rough machining then heat treating and then final grinding). I'm guessing that gassers use the keyway for indexing the manufacturing processes of the cam - since they have to have the keyway for installation in the vehicle - and diesel cams have the keyway cut for the same production indexing because that's how the production machinery is made.

__. I went over to the machine shop at Land Rover and spent an half an hour or so watching con rods being made but I didn't get that familiar with the process for cams.

Click to expand...

I'll second that idea and add that perhaps some of the industrial applications for this engine utilize a different TB system and perhaps use a woodruff key in those applications.

same cam blanks for gassers and diesels, gassers use the key diesels don't. simple enough no need to worry