How much resistance is too much?

[Mac-Porsche]

Might be a dumb, newbie question, but has me worried... Rebuilding '81, 911sc. Had all the heads completely rebuilt.

The crankshaft turned very freely by hand when timing the camshafts. However, after installing all the rocker arms, it seems to have a lot more resistance... I didn't notice this at first when setting the valve clearances, because you're only turning in 120° increments. Now that I'm all finished, trying to turn the crank by hand a full 360° in one motion, gives fairly significant resistances in certain areas.

Could this just be resistance from all the new valve springs? Is that normal? Or could something else be happening i.e. valves hitting pistons? I figured you'd be able to 'feel' the new springs, but wasn't expecting it to increase that much...

Any comments/suggestions are much appreciated!

[356911930]

This sounds normal. With all of the rocker arms installed you are also fighting the compression in the additional four cylinders. If you had valve to piston contact the crankshaft rotation would stop dead (unless you really pushed on the wrench hard and contact was minimal)

Best of luck with your top end rebuild,

Rahl

[911pcars]

Removing the spark plugs will open the chamber and allow easier crankshaft rotation for service procedures. And yes, the contact surfaces between open valves, rocker arms and cam lobes are high friction areas.

Sherwood

[Mac-Porsche]

It was after installing the spark plugs that it really became harder to turn. Makes a lot more sense now. I feel dumb admitting it, but I didn't think about the fact that I was closing the chambers by installing the spark plugs. Very new to this all, so I really appreciate the responses!