hi
what is everyone setting the lifter preload to on a hemi with hyd roller cam ?

around 580 lift as far as i can tell , no info on cam .

aluminum heads , aluminum rocker stands . iron block .


thank you !

1/4 to1/2 turn when cold and see how that works.
What amount of preload does the lifter maker want when hot?

no paper work on cam or lifter

was told it was a comp probably ?

also someone told me the hemi ex pushrod was likely to jump off the adjuster at start up if not enough preload due to steep pushrod angle after engine sits long enough for lifter to bleed down ?

any truth to that one ?

i found the lifter prelad on ex was 3 turns an intake 2 turns .

i resat it to 1.5 and have about 400 miles and 6 passes at the track and no issue so far .

was thinking about next step going to 3/4 turn on intake and 1 turn ex ?

what say yee ?

The stock ductile iron rocker adjusters are either 3/8x24 threads or if they have been upgraded and blue printed they would be 7/16x20 so when you due the math on the thread sizes for 1 Inch it works out to be on the 3/8x24 one ful turn of the adjuster equal .0416666 , I round it up to .042 per thread. The 7/16x20 equals .050 per turn, correct so that means a 1/4 turn on the 3/8 equals right at .0105 per 1/4 thread and the 7/16 equals .0125 per 1/4 turn.
Keep in mind the adjuster is on the short side of the rocker arms so the adjustment is multiplied on the valve stem side by the ratio of the rocker arms
I would start with 1/2 to maybe one full turn cold and go from their based on the iron block with aluminum heads and aluminum rocker arm stands, look at the time slips for guidance

If it was mine I would run 1.75 to 2 turns. Anything hydraulic I run about .070-.080 preload.

I believe Morel wants from .015 to .030 lifter cup preload away from the retaining rings
I use the minimum preload needed to make the lifters quiet so they won't pump up at high RPM(above 4500 RPM) and float the valves, I start with a 1/4 turn on iron heads on a iron block and 1/2 turn with aluminum heads on a iron block with 3/8x24 adjusters, a tiny bit less on the 7/16 adjusters

Hydraulic lifters can only pump up if valve control is lost. (So, valves would have to float or bounce first in order for that to happen).


If you have a valvetrain set up on the light side, or it's just unstable for whatever reason and it can get into loft/bounce, less preload would probably be better but I just try to avoid that alltogether.

I'm going to assume you have never floated any valves due to lifter pump up, correct?
I have seen it , especially in stock motors with weak valve springs The resulting damages can and are usually very expensive to fix, especially if a valve had breaks off

Yes to the question of have I done it but don't agree as to why.

My hemi before rebuilding had a hydraulic cam and the wrong valve springs. It would severely lose valve control at 5900rpm, at which point the lifters would pump up and hold the valves open and it would barely run for several seconds afterwords.


Valve float isn't -because- of lifter pump up.

Lifter pump up occurs because of valve float.


So, if there is a loss of valve control and the valve spring pressure is no longer consistently acting upon the lifter it's free to "pump up" to its internal retainer as nothing is holding it in position.

Your example of this happening on stock motors and weak valve springs is exactly what I am saying. It reaches a point where it loses valve control, lifter pumps up and bad things can happen.

To me the fix for that is getting the valvetrian under control for the rpm range you want to run it in or limit the rpm to a range it's still in control, not reducing lifter preload. (as it still hammers the hell out of everything).


To look at it another way, what is the piston diameter of a mopar hydraulic lifter? Don't have one in front of me but would guess around .650? So the area of that piston is .331 sq/in.

With 80psi oil pressure acting upon .331sq/in the piston is forced upwards by 26psi or so.

Stock 440 valve spring pressure is 130/180. Multiply that by 1.5 rocker ratio and the lifter "sees" 195/270 psi

The lifter can never generate enough force to just "pump up" against that pressure unless it's nearly/already floated the valves.


Well, it could with 600psi oil pressure. That's what it would take to overcome even stock 440 seat pressure.

hi

looked in my old 1998 crane catalog , it does not state any diff for roller or flat tappet lifter preload .

it states .020" to 060" preload .

that means .040" would be ideal = 1 turn of the 3/8" x24 adjuster .

so i sat the intakes at 3/4 turn and the ex at 1 turn for now .

ex were original at 3 turns causing the ex lifter to cut a small grove in the pushrod .

polished the pushrod damage area and ran them at 1.5 turns and no more contact .










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With aluminum heads you have to take in the expansion rate of the head and add preload accordingly. Make it an aluminum block and you need an extra .020 just for expansion. And yes, if the valve spring is not enough to control valve motion no amount of preload is going to matter.