Head Milling & Timing

[mpresley]

Can someone tell me how milling a head for an L6 affects valve timing and in which direction, too slow or too fast to open, and what the practical effects are?

[Noddle]

Can someone tell me how milling a head for an L6 affects valve timing and in which direction, too slow or too fast to open, and what the practical effects are?

 

Milling the head will shorthen the distance between the two sprockets( cam / crank ), thus making it retard the cam from what it would have been if it was not milled ( the tenitonier need to make up the extra slack in the chain, thus rotating the cam anticlockwise)

 

you may be able to get the timing back to what it was by using a different timing hole on the cam sprocket (most has 3 holes), or do what most people do, 'shim' the cam tower the same amount that was milled.

 

Nigel

[mpresley]

Milling the head will shorthen the distance between the two sprockets( cam / crank ), thus making it retard the cam from what it would have been if it was not milled ( the tenitonier need to make up the extra slack in the chain, thus rotating the cam anticlockwise)

 

you may be able to get the timing back to what it was by using a different timing hole on the cam sprocket (most has 3 holes), or do what most people do, 'shim' the cam tower the same amount that was milled.

 

Nigel

 

Thank you. I will see if the machine shop has material for shims.

[SleeperZ]

If you are milling it to correct for warpage, make sure you mill the top surface too, to keep the camshaft true.

[mpresley]

If you are milling it to correct for warpage, make sure you mill the top surface too, to keep the camshaft true.

 

Thank you. I would not have thought of that.

 

Life is complicated.