How does cam timing affect DCR?

[Carnut427]

Originally Posted by blykins

If I retard the cam timing 4 degrees (by keeping the cam in the current spot and rotating the crank CCW to accomplish it), then the piston would move lower in the cylinder. Correct?

If that's true....then essentially the intake valve on is going to be open for a shorter period of time relative to the piston than with the cam timed straight up.

If I'm still thinking on the right track.....

With the cam timing straight up, the intake valve closed at 50 deg (@ .050") ABDC.

Now with the cam timing retarded 4 degrees, then that number should decrease.....correct? It should be 46 deg @ .050 ABDC.

So theoretically, if I choose to retard the cam timing, then my DCR should go up....and I'd have to choose a thicker head gasket to compensate.

Right?

Sorry to disappoint you, but I'm not Ernie.
There's no such thing as a stupid question, especially on this subject, as it's confusing...Everything you've said is correct except what you're describing is advancing the cam, because you're making the valves open earlier. Really easy to get confused here. This would increase low end and decrease top end power. It would also have a greater tendency for the intake valve to hit the piston, as the intake is opening faster than the piston is moving down. Always check piston to valve clearance when moving a cam, just as you would when changing cams.
Moving the cam as you explain (advancing it) would indeed increase the DCR, as the piston has more time to build compression.
A cam closing @ 50* ABDC is fairly mild...what's your compression ratio and resulting DCR with the cam straight up?
Dan