Everything came apart right after our last race for a freshen up. I'd been keeping a good eye on the camshaft all season as several of the lobes were starting to look pretty herky. The valve lash wasn't changing but toward the end of the season I felt the car was off .05-.07 from where the last dyno numbers were and what the weather records showed it should have run. It also started to not be responsive to changes...a sure sign something limiting the tune up.
The leading/trailing edges of the lobe ramps looked like this on disassembly:
The 'dwell' style lobes we use on the Stockers are pretty different. Basically, they lift the valve extremely quick and then transition very fast to the top of the lobe where it 'dwells' for quite a while, then slams shut quickly on the closing side. My engine specs are .390 intake and .410 exhaust, so you don't have much to work with, anyway. It takes a fair amount of valve spring pressure to keep the lifter on the lobe and to not loft it as it goes over the opening ramp or have it crash the lobe on the closing side. The result is you have a tremendous amount of pressure being applied to a very small area of the lobe. We dance around with nitriding, cryo, REM polishing, lifter face oiling holes, reading the alignment of dry chicken bones placed by Swedish virgins in the moonlight...but the bottom line is these things just have a life expectancy. No complaints on this one as it had over 200 passes plus dyno sessions on it.
Everything is back from the precision machining wizards at Victory Engines in Marshall, Mn. and going back together. Several days were spent tweaking different oil ring packages to lighten up the drag a skosh more. Sorry...no 'eye candy' in these Stock engines.
Matter of fact, they are downright boring to look at.