I'm way out of my depth here (and apologies Daniel as I think I'm segueing off topic); but I thought the only reason you wouldn't need to adjust valve lash in an engine was if there was a mechanism which allows the engine to do that itself, eg. the hydraulic lash-adjusters ... hence me asking if there's any chance something which does that job needs attention.
Or is no such mechanism needed in pushrod engines?
It's not pushrods engines that are not adjustable, just the LS which users hydraulic lifters and roller cam along with other engines that use the same tech.
There are no lash adjusters in these engines.
But I guess a bent push rod or stuck lifter counts as adjustment!
Just wanting to learn more…
I always understood the LS3 hydraulic lifters uses oil to automatically provide zero lash adjustment. The lifter internal bore which contains a piston within the lifter itself would fill up with oil and take up any slack. As such the pushrod pressing on lifter piston and the rocker itself would have zero lash and the engine would be nice and quiet during operation. Seemingly simple but actually a complex device I don’t fully understand.
If the lifter would bleed down due to the engine standing unused for some time, the valve train would clatter away on startup until the lifter piston reservoir filled up with oil and lash was returned to zero. That’s why some engines sound so tappety in the mornings.
If a lifter is faulty, due to some oil crud getting inside or wear because of faulty tolerances or metallurgy or wrong oil viscosity?, it may cause some issue with the lash adjuster mechanism within the lifter itself. The lifter could more easily bleed down and thus noise or pump up which causes other problems.… I think this is what Forg was getting at in that a lifter may be faulty…
Again as I understand it, LS3 lifters provide this hydraulic lash adjustment. So when we talk of lifter preload, I understand it’s to position the lifter internal piston that the pushrod rests on within the middle of some defined position within its possible stroke (within the lifter body itself).. and in this context t a bent pushrod upset this preload which can cause issues itself.
Have I understood the comments correctly and how the LS3 valve train lash & preload works? cause my head hurts now
