Hyd lifter mods

[L89 chevelle]

In a hyd lifter is there any reason not to increase the size of the oil inlet hole to help minimize lifter bleed down at high rpm's.

[rookie]

Good question!

[Cammer]

Read the following closely and you will get some good ideas:

Variable duration hydraulic valve tappet - Patent 3921609

[L89 chevelle]

Originally Posted by Cammer

Read the following closely and you will get some good ideas:

Variable duration hydraulic valve tappet - Patent 3921609

That aids in bleed down, I want to prevent bleed down. I would think another way would be a smaller hole in the pushrod puck like a solid lifter. ( .025 vrs .073 )
Anyone tryed this?

[rookie]

Have you read this Hydraulic Lifter Power - lashing for max rpm!
DV wrote about this same type of adjustment on flat tappets in his, How to Build Max Horse Power Budget Small Block Chevy book.

There is also a thread on this forum about it.

[L89 chevelle]

However if the lifter collapses (and this applies mostly to roller lifters) the whole valve train goes to pot. If the lifter has a propensity to collapse then we need to tackle the situation by limiting just how much it can collapse. The extreme case here is to adjust the lifter all the way to the bottom of it’s travel so there is no further travel for it to collapse into. The down side of this is that we now have, in effect, a solid lifter and no lash clearance. By adjusting the lifter to within say ten thousandths of the bottom of the travel we are getting back the hydraulic action require but limiting any collapse to just ten thousandths. In practice most rollers will collapse this amount and recover during the closed part of the cycle so that lash continues to be taken up as intended.

Here is how we deal with hydraulic roller collapse. This 5.0 small block Ford lifter has had two washers (of about 0.090 thickness) installed at the point arrowed. The spring is removed and the round wire clip is replaced with a stout snap ring. (circlip)

The same effect can be achieved by installing washers or a travel stop of some sort into the lifters innards. This means the lifter may only have ten thousandths of hydraulic travel. Going this route compensates for a poor lifter and the limits of a less than perfect valve train. This, for a high performance application is my choice.

What causes the lifter to collapse? Oil supply verses leakage? These mods are not fixing the collapse just working around it by making the lifter more like a solid.

Dusty?
DV?

[rookie]

May be this will help.
Hydraulic roller race oil - what's it worth???

[Cammer]

You need to read the whole patent. Many good ideas to control lifter flow are explored.

[Packard V8]

There are two different problems associated with hydraulic lifters at higher RPMs:

1. Lifter pump-up. When engine RPM exceeds the ability of the valve spring to control valve motion, the valve floats. The hydraulic lifter sees less pressure and more clearance. It "pumps-up" to the maximum of its travel. When the valve comes back in contact with the rocker, it is held open by the maxed-out lifter travel. More spring pressure and better lobe design postpones this effect.
2. Lifter collapse. To try to control the valves at higher RPMs, the valve spring rate is increased. At some point, the valve spring rate and lobe intensity overcomes the oil pressure in the lifter and pushes the piston to the bottom of travel.

In either case, the only real answers are:

1. Stop winding the juice lifter motor so high - it ain't made for that.
2. Get rid of the juice lifters and go with solids. Racer or poser? - the lifters are the difference.

thnx, jack vines

[rookie]

Beehive springs and Hollow stem valves has changed rpm limits big time on Hyd. lifters.