Lifter Preload Question

[NelsonATC]

I measured preload today using a dial indicator.

Procedure:

Torqued down rockers to spec.

Rotated the engine half a dozen times.

Set up dial indicator on the oiling hole on the rocker arm (so it was directly above the pushrod).

Released torque on the rocker bolt (this brought me to .040 on the indicator)

Released torque on the bolt for the rocker on the opposite side of the bridge (this brought the indicator to .170)

This was repeated 3x with results =/- .010


My block was decked .000, Shop told me he took very little off the head, maybe .006. All told, .033 + .006 = .0.039 taken off?. Stock replacement cam and lifters (Sealed Power)

So why am I .140 long on the rods? was the preload too high from the factory?


Anyhow, here is my math:

Stock Pushrod length = 9.625

to get to .020 preload I would need a 9.475 rod

to get to .060 preload, I would need a 9.515 rod


Am I missing anything?

[IH 392]

You didn't figure in your valve stem height, what is it??, and pushrod length needs to be figured AFTER the rocker arm geometry is figured and set!

[NelsonATC]

No your going way over my head. I don't remember reading anything about this.

Valve stem height? I have no idea how it even measure this.

I guess it would be whatever is stock to the jeep 4.0 head.

[Cheromaniac]

Anyhow, here is my math:

Stock Pushrod length = 9.625

to get to .020 preload I would need a 9.475 rod

to get to .060 preload, I would need a 9.515 rod

Am I missing anything?

Yes. The lifter preload should be ~0.040" from the factory with 9.625" pushrods and no decking of the block/head. If you've had a total of ~0.040" taken off the block/head, the lifter preload should now be ~0.080". To restore it back to its original value, you'll need 0.040" shorter pushrods. The nearest size available is 0.050" shorter at 9.575".

[NelsonATC]

That was my initial thought, take the original length, subtract the deck work, and I have my pushrod length. But I saw so many threads on there about measuring preload, so I decided to take that route.

Was there a flaw in my precede? I have used a dial indicator before, so I know my reading are correct. It pisses me off to not know why this measurement is off.

9.575 Pushrods. The only ones that come up when I search are for racing applications at $200+ set. Do you have another source?

[dwg86]

I used trend pushrods in my engine. One piece, .080 thick, chrome molly pushrods cost me $80.00 shipped to my door(that was a couple years ago). Buy a pushrod length checker. They cost around $20.00, but this is the easiest way to make sure you are getting the correct length.
http://trendperform.com

I have also hear good things about smith brothers pushrods. I don't know about thier prices...
http://www.pushrods.net/

[dwg86]

I measured preload today using a dial indicator.

Procedure:

Torqued down rockers to spec.

Rotated the engine half a dozen times.

Set up dial indicator on the oiling hole on the rocker arm (so it was directly above the pushrod).

Released torque on the rocker bolt (this brought me to .040 on the indicator)

Released torque on the bolt for the rocker on the opposite side of the bridge (this brought the indicator to .170)

This was repeated 3x with results =/- .010


My block was decked .000, Shop told me he took very little off the head, maybe .006. All told, .033 + .006 = .0.039 taken off?. Stock replacement cam and lifters (Sealed Power)

So why am I .140 long on the rods? was the preload too high from the factory?


Anyhow, here is my math:

Stock Pushrod length = 9.625

to get to .020 preload I would need a 9.475 rod

to get to .060 preload, I would need a 9.515 rod


Am I missing anything?

I don't understand your math. You say .000 was taken off the block and .006 off the head, where are you getting .033+.006=.039 taken off? The math is correct. I just don't see the .033 any where? I think you need to look at one valve at a time. When you lossened the other rocker on the bridge, that valve may have been compressed some. Whatever rocker you are going to check... make sure that cylinder is TDC with both valves closed.

[NelsonATC]

I mean the block was decked to .000. He took off .033. The measurement was done on c # 1 @ TDC.

From what I see? Both rockers need to be loosened, as the bridge setup puts pressure on both rockers.

I will get the pushrod length checker this week.

[Cheromaniac]

Anyhow, here is my math:

Stock Pushrod length = 9.625

to get to .020 preload I would need a 9.475 rod

to get to .060 preload, I would need a 9.515 rod

Am I missing anything?

Yes. The lifter preload should be ~0.040" from the factory with 9.625" pushrods and no decking of the block/head. If you've had a total of ~0.040" taken off the block/head, the lifter preload should now be ~0.080". To restore it back to its original value, you'll need 0.040" shorter pushrods. The nearest size available is 0.050" shorter at 9.575".

My bad. The nearest size is 0.025" shorter at 9.600" and Crower have a set at http://www.summitracing.com/parts/cro-6 ... /overview/
The Crane rocker arm bridge shim kit carries part no. CRN-99179-1 and it has shims of 0.030" and 0.060" thickness. If you can't get the lifter preload in the 0.030-0.060" range (half to one full turn of rocker arm bolt from "zero lash" point to 19lbft torque) using the shims alone, you'll need the shorter pushrods.

[IH 392]

Rocker shims are to adjust the rocker arm geometry not the lifter preload.

[NelsonATC]

Rocker shims are to adjust the rocker arm geometry not the lifter preload.

It would also adjust preload by default as well, no? But I also don't want to screw with the geometry, since it should be fine. I made no changes to the valves, spring(new stock replacements) and am using the original rockers and bridges. Nevertheless, I will check it out to be sure.

[Cheromaniac]

Rocker shims are to adjust the rocker arm geometry not the lifter preload.

Actually they do lower the lifter preload but I agree that altering pushrod length is a better way to adjust the geometry. Ideally adjustable rockers is the way to go.

[IH 392]

I can't seem to figure out WHY!?? everyone is OBSESSED with getting the lifter preload back to exact factory specs but on the other side of the same coin they TOTALLY! disregard rocker arm geometry?, I've assembled well over 1000 engines! and NEVER ONCE! checked lifter pre load!, the HYSTER forklift engines that were run on LP fuel would come back in the shop with the exhaust valve seats beat (melted) out to well over .1000" recession, the lifters would soak up every bit of the failure without issue!, the engines would be sent back in because the valve guides would have about .030" of wear in the shape of an hour glass from the rocker geometry going to hell and wouldn't seat worth a crap any more!

I guess I can't figure out why everyone just wants to do a halfassed job on their valve trains?

[NelsonATC]

So what you're saying, is that I should not go under the assumption that the Valvetrain geometry is correct from the factory.

As I stated before, I am running stock rocker arms, stock bridges, replaced springs to stock specification, and stock valves. What should I be looking for? What measurements should I be taking?

FWIW: My builder said the same thing about lifters. He told me not to be concerned about the pushrod length, as the hydraulic valves would soak it up. He told me to run the stock pushrods. This is is an experienced builder. However, I didn't think it would hurt to measure pushrod length with a length checker And see where the numbers came out

[IH 392]

If your valve and or seat have been faced the valve stem protrusion is out of spec, any REAL cylinder head machinist will measure this and correct it by grinding the stems back to the correct protrusion, personally I wouldn't assume that this has happened!?, and even if it has been done assuming that it is correct isn't a good one!, if you're dumping lots of $$ into a new engine go all the way and make it right!
This should confuse the issue quite a bit!?
http://www.aera.org/ep/downloads/ep10/E ... _20-30.pdf