When your hydraulic lifter equipped motor idles like shit, and you swear you've tried everything, it can be a weak/broken valve spring. Broken is easy to check, but not so easy if it's weak. On adjustable rockers try zero lash and listen to the motor or watch a vacuum gauge hooked to a direct source. Rocker shafts can be shimmed. The lash may make for a solid lifter sound, but the motor will respond audibly smoother. If adjusting/shimming isn't practical, and you're lucky enough to just have ONE bad spring, you can twist a large screwdriver blade between the coils of the valve spring while idling to simulate a stronger spring. All while listening, or watching the vacuum gauge
perhaps its a good idea to have your springs tested before installation? would a machine shop do this simple task if asked?
Yes, but this is more aimed at an older motor, but it would still be applicable in a new motor that used springs were put in
I have gotten the same response out of a motor that had poor guide work- if you pushed one spring/valve assy toward the motor with your thumb while it was running, the valve would seal up and it would smooth out. the tavia spring pressure testers work well, too. certianly not as low buck of an approach, but after seeing a set of new springs vary by as much as 20 l.b.s. on a bench type tester, being able to test on the head is nice.
lux blue mentioned the tavia spring pressure tester: http://www.tavia.com/cat8.html $80.00 isnt out of this world. whats a good way to prevent oil from splashing all over the engine compartment? ive got some clips that install over the oiling end of a chevy style rocker arm.. im going to assume most non chev style rocker assemblies have an oil hole?
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