[steve25]

Let’s get some basics nailed down that can’t be disputed..

1)
Your lifters as you have posted have about .050” of adjustment range that they will work in just fine without noise if there made right.

2)
as any motor heats up any dimension that was a clearance will close up some and other will open up.
3)
As valve seats bed in and ware over time and valve stem tips and rocker arm tips ware what might have been a no gap / clearance condition will develop a gap.
4)
Aluminum heads will typically grow about .005” to .008” when up to normal operating temp, and iron heads will grow about 1/2 that amount.

Basically all you are doing when adjusting a hydraulic lifter is providing enough room for dimensions like above to change while maintaining a no clearance condition and also keeping the plunger from coming up against the clip ( be it round or flat C type) to hold the plunger from exiting the body of the lifter.

So basically you have been told in your corespondence that if you have a given push rod length that gives you good geometry at half lift then a push rod .020” longer will have the plunger compressed .020” out of that .050” you have to work with .
This is fine and as dimensions change when the motor is hot and things ware some you should never hear a clacking lifter or rocker.

[Jay S]

I would subtract the .020” for the correct pushrod length with a VPro.

[MPKind]

Originally Posted by Jay S

I would subtract the .020” for the correct pushrod length with a VPro.

I've read past posts from you about V-Pros and it looks like you've used them a number of times. Thanks for your input. I would also lean toward subtracting 0.020" from the initial measurement that has the rod bottomed out and the rocker at a good spot, perhaps slightly more to move the rocker to mid-lift in the upper RPM (above 3500) range. Maybe that's getting too picky. My setup will use 0.020" lifter adjustment once the new rod is in place. That'll get the plunger just off the bottom of the lifter. 0.013" - 0.014" approximately, then as RPM increases the plunger will move up to provide full valve lift, duration, and velocity. At least that's the theory.

[77 TRASHCAN]

Originally Posted by Jay S

I would subtract the .020” for the correct pushrod length with a VPro.

Jay, didn't you build a 455 recently with V-Pro's? Could you tell us about how and why you set up your V-Pro's on that engine?
THanks
Jeff

[Jay S]

Originally Posted by 77 TRASHCAN

Jay, didn't you build a 455 recently with V-Pro's? Could you tell us about how and why you set up your V-Pro's on that engine?
THanks
Jeff

When starting from a pushrod that is a set length, adding .020” (as Rhaod’s said) to the length then checking the pattern with a pushrod checker is correct. If you’re starting out using a pushrod checker with no idea what the length may be, to get the actual pushrod length you subtract the .020” from the pushrod checker length. What Rhaods was suggesting was not wrong, they were just starting from a set pushrod length, versus starting with a checking tool. In other words, for finding what the operating contact pattern of the rockers with V series Rhoad's, one way you add lash to the length, the other way you subtract it.

Vpro’s have an extra shim in them to raise the plunger so they can be set with less lash than a Vmax. If you follow the instructions for Vpro and Vmax with their corresponding recommended lash settings the plungers operate at the same height for both the Vmax and the Vpro. With the combination of the shim under the plungers and adding the .020” lash on a Vpro the position of the plunger is pretty close to the same as a regular standard lifter with 1 turn from zero preload. In other words the pushrod length for a Vmax or a Vpro is the same as standard lifter. I never seen that a different length pushrod was required on a Vpro versus a standard regular lifter. A Vmax running a ton of lash to pass a vacuum rule of a racing class might take a different length pushrod than a stock lifter, but for most street stuff the pushrod lengths will not change from a standard lifter. You can switch to V series lifter and use all the same valve terrain parts as regular lifters use.

[MPKind]

Originally Posted by steve25

So basically you have been told in your corespondence that if you have a given push rod length that gives you good geometry at half lift then a push rod .020” longer will have the plunger compressed .020” out of that .050” you have to work with.

I agree with everything about wear and heat expansion. The V-Pros are adjusted from the bottom up using a feeler gauge at the valve to loosen or tighten the reduction in valve lift, duration, and velocity vs. from the top down to set a pre-load. So that's the conflict. Adding length if you're setup starts at the top of plunger travel makes sense, but all the published tech info at Rhoads emphasizes the bottom up procedure. Adding length to a rod that's already bottomed out seems counter-intuitive.

[Jay S]

If you know what the cam profile looks like (can measure this when a cam is installed) a good general rule for the street is to not set the V series plunger clearance so they operate looser (once the engine is hot) than where the tappet lift of the cam has 1* per .001” of tappet lift on the closing side of the cam. To find that, multiply that tappet lift by the rocker ratio for the max hot clearance. Generally that is the most clearance (hot) that a V series lifter is able to operate well on for the street. It is the quietest operation for the profiles performance gains with V series lifters. Going beyond that is also excessively hard the valve terrain.

I don’t use the Rhoad’s instruction blanket numbers for clearance, because the profile does make a large difference in how the lifters perform.

For a Compcams XE profile, it hit that acceleration at .006” tappet lift. All these cams have the close to the same acceleration at the clearances.

.006” X 1.65 = .0099”

On the exhaust with the magnum profile the same tappet acceleration is at about .007”

.007” X 1.65 = .0115”

For a Melling SPC-8, It hits that tappet acceleration at .009”
.009” X 1.65 = .0148”

For a Crower 60919, it has gentler ramps yet, it hit that same acceleration at .011”. Nearly twice as gentle ramp as an XE.

.011” X 1.65 = .0185”

For racing purposes it is fine to set the clearance higher than those numbers. But for the street, the valve seats and guides get beat up excessively if running more clearance than those clearence numbers.