Checking lobe lift

OldmanRick said
I'm leaning this way myself. If the stylus on your DI is long enough to reach the lifter cup, pull the rocker shafts and and pushrods and let it sit for a while. The DI wont put hardly any pressure on the lifters and they should stabilize enought to give you a close enough reading to see if a lobe is going flat or not. With that said, if you had a wiped lobe you'd be getting some racket out of it any way. Cam lobes generally don't just wear a little. When they start to go, they go.

Thanks Rick. I had planned on measuring with the rocker shafts removed and pushrods in place. I was just going to put a socket or something next to the pushrod to stabilize it while while measuring and then set up the DI to take a measurement from the pushrod tip while I turn the crank over by hand. If I've wiped a lobe I thought it should be pretty apparent.

I have a 5,000 RPM misfire and occasional valve noise that I'm trying to sort out. I have a good feeling that the valve springs are shot so I'm going to replace them and thought I would check whatever else I could while I'm at it. As for the valve noise I suspect that the lifter preload may be off, or maybe the lifters are just bad. I Just measured the pushrods and they range from 8.549"-8.556". I'm going to measure the preload next to see if any of them may be too short for whatever lifters are in there.

Once I have all these measurements I should have a much better idea of what's going on.