Help with Valvesprings and valve float. Noob
And yet, even when you adjust the “hi rpm” lifters to .002-.004 lash(so they can’t “pump up” and hang the valves open)...... they still exhibit the exact same problem.....and that problem disappears when the lifters are swapped for solids.
(Just like they discovered in that article).
I have done this on the dyno numerous times........ on several
different engine platforms.
Hyd flat and hyd rollers.
There’s a reason things like limited travel and Shubek style lifters exist........ and it’s because normal hyd lifters don’t cope very well with fast rate lobes, high rocker ratios, and the associated spring loads required to allow for high rpm use.
Sell him a correction kit........ see if it cures his problem.
If it does...... it’ll be his cheapest way out.
Well, we have different experiences. I didn't say the anti pump up would be equal to the improvement of a solid, only that it would improve, similar to a solid. The solid lifter will tolerate a lot more spring pressure, so obviously it can do a better job of masking valvetrain instability from poor rocker geometry. I personally won't let a motor go out the door without making sure the geometry has been addressed. I do, however, go up in rocker ratio on most of my combinations. My personal street car has a Comp XE-HL with a 1.7 ratio, and the recommended catalog spring, and it doesn't fall off a cliff or pop. No trick lightweight parts either.
Increased spring pressure is obviously going to make a hydraulic lifter compress more, and cause the plunger to fluctuate, especially with harmonics involved. But, that helps make my point of not putting on more spring pressure than necessary. Get the geometry right, and you will know how much, or little, spring pressure you really need. I had an engine builder who removed 120# of open pressure after correcting the geometry, turned the same rpm as with the heavier spring, and turned considerably more rpm on the dyno than with the heavier spring and no correction. I don't recommend that unless someone has the ability to do thorough testing to see where the limits are, and I don't even suggest pushing the limits to begin with. It's simply an example of how settling the valvetrain down requires less spring, even with a hydraulic setup. I can truthfully say, I've never had a customer tell me they didn't see a marked improvement with corrected geometry, when they had a problem with valvetrain instability prior to the change.
And finally, I don't suggest correcting geometry just to sell a kit. They aren't a big money maker anyway. I provide that insight for free, and if it comes back to me in business, and I've helped someone have a better engine, everyone is happy. If the OP has a local shop that actually knows what they are doing, he could have them relocate the rocker shafts and get the geometry right, but likely for a much higher cost. I HOPE by giving that insight people will do business with me, and the I'm sure same applies to you and the advice you share. FWIW, the OP hasn't mentioned what rockers he is running yet. It would be helpful to know all the valvetrain parts we are dealing with here.
