Difference between heads hyd flat vs roller

flyfish said
I disagree. Lifter weight has a LOT to do with spring selection, especially when you consider the inertia of the lifter at high RPM. It will take a lot more spring to control a heavy lifter, than a light weight lifter (one of the reasons high RPM engines need light valvetrain components)....think about it critically for a moment, I'm sure it will make sense.

Simple illustration: Shake a can of soda at a steady rate of 5 shakes per second, now try to do the same with a gallon of milk....it will take a lot more force to control the milk because it weighs more (more inertia). Now imagine the magnitude of a small increase in weight at 7000RPM....I hope that helps.

Ok. But there has been so much testing on this it’s ridiculous and redundant. Weight on the pushrod side of the valve train has very little consequence as far as performance and such are concerned. That’s a well known fact.

The valve side of the system is where you need to save weight. Simple as that.

You can (and must) run more spring load with a roller lifter because of the shape of the lobe. It’s how aggressive the lobe is that requires more spring load, not the weight of the lifter.

That’s an issue with hydraulic lifters of any type. One is you put a shock absorber in the system. That’s bad. And two, the hydraulics won’t take much spring load. That limits RPM. Too much spring load and the hydraulics collapse.

I’ll say it again...lifter weight is not a function of spring load.

In fact I have another example of pushrod side weight stupidity. When I first started doing this stuff guys were running pushrods there weren’t much stiffer than a noodle. Most guys still don’t run a stiff enough pushrod. One of the first things I learned was a 3/8 pushrod is pretty much worthless with any kind of a decent roller lobe. Will it run? Yes. Is it right? Nope. I went from some high dollar 3/8 pushrods to 7/16 pushrods and gained a bit over 500 useable RPM and something like 12 HP everywhere. I gained more going to a double taper (3/8-7/16) pushrod when all the whiz bang’s in gym shorts said it would be a power loser.

Lifter weight (within reason) is insignificant.