Quote:
Originally Posted by Steam Driver
The engine in question is an ‘82 SC, stock cams. I have already searched the forums about this, along with the tech articles and Wayne’s book. The issue drives me nuts!
How do you keep the cam from rotating from valve spring pressure after you have turned the engine to overlap and reached the desired value? I find there is usually a lot of pressure resisting dowel pin removal, and when it finally comes out the dial indicator reading jumps about half a millimeter.
To me this is the difficult part of 911 cam timing, the rest is straight forward. I must be missing something here; what is it?
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if you are timing the valves with the intake lift method, fit 1 intake rocker to the 1/2/3 side only and do the lash. rotate the crank backwards past TDC and then rotate the crank clockwise but about 20° BTDC or about close to where the lift number you need will be at TDC. Fit up all of the drive parts and your indictor. Turn the crank until you get your desired lift. Then pull the pin and rotate the crank either clockwise to TDC or backwards past then clockwise to TDC. Fit the pin. tighten the nut or cam bolt, rotate the crank until you come back around to TDC and see what the lift is. Repeat until you get the number you need. The cam will not move. If it does for some reason, keep fitting the pin, checking and adjusting until you get it right. Remember there will be some play in the dowel pin so you can get the number you need on the nose. Typically if you error on the "hole" just before TDC the slack in the pin to hole will allow you to end on the nose.
If you want, you can remove the rocker from the # 1 cylinder , turn the engine 360° and repeat for the # 4 cylinder. Once the cams are set, you can go ahead and fit each rocker one by one and perform the lash.
A good check once you are all done is to rotate the engine until you achieve full lift on each valve and check against reference marks on the crank pulley. You may be surprised that they are not the same. This can be camshaft errors or rockers are re ground and the faces are not the same. If you see some differences and decide to leave, you can then understand why there might be some idle RPM differences.