Now i have .040" pre-load on the hydr lifter.
Is it possible to change to solids on a hydraulic cam?
What/how does that benefit? Does that also reduce duration?
You can run solids with a tight lash setting (.004-.006" etc.), but the ultimate fix for low vacuum, weak low end response is the V-Max lifters by Rhoades. You can use them on hydraulic cams and even solid FT cams to operate without lash! The way to set them is: set the cam position to base circle, run the lifter plunger TO THE BOTTOM and then back off enough to get a .010-.035" feeler gauge in there (more thickness here means more duration reduction/more vacuum increase) and then tighten until it drags-through like setting a solid lifter lash. When you remove the feeler gauge, the internal spring closes the gap so there is never free play. When the engine is started, the V-Max lifter fills with oil and maintains a low pressure inside the lifter (due to bleed-off) and lets the valve remain seated until the plunger bottoms and the valve is forced open, AFTER the lifter shell has moved upwards the amount of the feeler gauge setting. This (time) is how the cam is made "smaller", and it bleeds down less and less as RPM (oil pressure/volume) increases, until at some mid-rpm (some say 3000, others 3500-4000) the lifter cannot bleed off enough to alter the duration (change the TIME) of the actual valve events from the shape of the cam lobe. It basically separates (to a degree) valve action from lifter travel, via the plunger oil bleed-off.
