Author Topic: Valve Stem Wear Signature  (Read 3491 times)

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Thumperbird

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Valve Stem Wear Signature
« on: December 28, 2018, 12:34:04 PM »
Hello,

Going thru the top end of my engine after 1st summer of run time.

Edelbrock heads, Harland Sharp adjustable roller rockers.

On the valve stem tip I am seeing either a straight across wear pattern about 3/16" wide or a bow tie looking shape which implies valve is rotating a bit, about the same 3/16" wide pattern just clocked.  Both are centered on the stem tip fairly well.  This is not a high wear thing, more of a polish.

Should I be worried about any of this?

Thanks.



blykins

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Re: Valve Stem Wear Signature
« Reply #1 on: December 28, 2018, 04:11:33 PM »
A 3/16" wide pattern is huge.  Most roller rocker wear patterns on the valve stems are usually around .040-.060". 



Brent Lykins
Lykins Motorsports
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Thumperbird

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Re: Valve Stem Wear Signature
« Reply #2 on: December 28, 2018, 07:23:46 PM »
Poor guess on my part but sounds like it is still a lot.
Measured ~.120". 
Here is geometry minus rods, did not do any shimming of rocker arm.
Adjusters are about 1.5 turns from bottomed out in the arm.
Thanks

blykins

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Re: Valve Stem Wear Signature
« Reply #3 on: December 29, 2018, 06:41:33 AM »
Sometimes you gotta shim, sometimes you gotta mill.  But a wide pattern is not optimal.  Not only are you spreading the load out over outboard areas of the valve stem, but you are losing a lot of lift to wasted rocker movement.
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
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Thumperbird

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Re: Valve Stem Wear Signature
« Reply #4 on: December 29, 2018, 08:57:57 PM »
Let's see if I understand this geometry thing:

Since the rocker is effectively a pivot it's travel arc/distance is unchanged regardless of geometry between the rocker and the valve stem, the roller arm moves the distance of the lobe height x the rocker ratio.  However if there is rod movement on the ball that will have impact on lift as well.

If the tip of the valve stem axis were perfectly parallel (stem tip perpendicular) to the arc of the rocker at all times there would be no sweep and therefore no loss in valve travel.  Of course this is not possible. 

Assuming an out and back sweep, the loss in valve lift is ~ equal to 1/2 the cosine (valve stem axis to rocker arc angle) x sweep.  This is ever changing in reality so above is a simplified formula for sure.

From what I can see, in a general sense, it is best to set the rocker shaft centerline ~1/2 the total lift below the tip of the valve stem.  This would cause a sweep out for the first 1/2 of the lift and an equal sweep back in for the last 1/2 of the lift. 

There is some additional adjustment to consider when looking at the rod side of things, I suspect a similar situation in terms of minimizing the sweep if you will of a cup on the ball, one would want to minimize rod movement off the centerline of the ball.

Am I close?

If logic is close, I would need to cut ~.1" off of the rocker stands which will make my rods too long.

Thanks.     




Tobbemek

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Re: Valve Stem Wear Signature
« Reply #5 on: December 30, 2018, 03:46:21 AM »

fastf67

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Re: Valve Stem Wear Signature
« Reply #6 on: December 30, 2018, 10:33:16 AM »
https://www.youtube.com/watch?v=o5is9BsH5OU
Will show you the way to set up the valve-train explained simply.
 
https://www.youtube.com/watch?v=RjaosX63DkM
Will show you how to check your valve stem to rocker pattern and also if your getting the most out of your valve-train or have wasted movement as mentioned.

For most cams a 3/16 wide pattern (.1875) it should be pretty obvious there is a hard or incorrect rocker angle. Yes, I believe the valve has rotated and has giving you a false reading as to the contact patch. Valve train instability, worn guides, ect. can show a wide contact patch. Simple to go back and check.

Arizona ‘58Mercury

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Re: Valve Stem Wear Signature
« Reply #7 on: January 01, 2019, 01:31:56 PM »
Watched that video, super simple. On geometry.  1 question came to mind however and he didn’t address it. Maybe I’m over thinking it.  Was he seting that up for solid lifters?   I didn’t hear any mention when he was setting up the pushrod to get length about allowances for hydraulic lifter compression.  If running hydraulic lifters is there a standard amount added to account for them?   Thanks


fryedaddy

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Re: Valve Stem Wear Signature
« Reply #8 on: January 01, 2019, 01:58:36 PM »
i run hs rockers on my 428.the instructions that came with the rockers says there needs to be 0-2 threads sticking out the bottom of the rocker.you said yours are 1-1/2 turns from bottoming out.i think your pushrods might be too short if you have to screw them down that far.im no expert.im just going by the directions.
1966 comet caliente 428 4 speed owned since 1983                                                 1973 f250 ranger xlt 360 4 speed papaw bought new

blykins

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Re: Valve Stem Wear Signature
« Reply #9 on: January 01, 2019, 03:59:46 PM »
Watched that video, super simple. On geometry.  1 question came to mind however and he didn’t address it. Maybe I’m over thinking it.  Was he seting that up for solid lifters?   I didn’t hear any mention when he was setting up the pushrod to get length about allowances for hydraulic lifter compression.  If running hydraulic lifters is there a standard amount added to account for them?   Thanks

On a hydraulic cam, you measure for pushrod length at zero lash/preload, then add the amount of preload that the manufacturer recommends to the length of the pushrod.  On most FE hydraulic setups, I run .050-.060” of preload.  Short travel lifters are another animal.
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
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Thumperbird

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Re: Valve Stem Wear Signature
« Reply #10 on: January 01, 2019, 08:56:29 PM »
Fryedaddy,

They are about 2 turns down from all the way up, not screwed out a long ways so that is not an issue.  I set the preload pretty much as Brent stated, at ~0.060, I believe it was a 1/2 turn of the adjuster.

With that said, could not have screwed this up any more if I tried, not sure why I brain farted and just installed the Harland Sharp rockers as is.  Here is where I was and need to be it looks like. 
Does anyone have a gut feel on whether or not I will notice this difference in terms of engine behavior?

As found = no shims under rocker stands, ball/cup rods are 8.315" long.  Sweep well over .100".   Rod axis not aligned all that well with adjuster axis.

As needed = .25" shims under rocker stands, ball/cup rods need to be 8.725 " long, this moves adjuster up into the rocker farther than before and of course accommodates the .25" shim.  Rod to adjuster axis will be more straight line now as well, cup not eschewed on ball.

What was I thinking....in too much of a hurry to get it on the road last spring I guess.

Thanks.

Arizona ‘58Mercury

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Re: Valve Stem Wear Signature
« Reply #11 on: January 01, 2019, 09:05:31 PM »
On a hydraulic cam, you measure for pushrod length at zero lash/preload, then add the amount of preload that the manufacturer recommends to the length of the pushrod.  On most FE hydraulic setups, I run .050-.060” of preload.  Short travel lifters are another animal.
[/quote]


Okay Great!!  Thanks Brent,  I will be reaching out about a set of those rockers later in the year too.

wowens

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Re: Valve Stem Wear Signature
« Reply #12 on: January 02, 2019, 07:48:58 AM »
FE rocker arm assembly's were designed by Ford to have drip tins which shim the stands up. Put .060 shims under one side, magic marker the valve tips, roll engine and check it. I bet your sweep will go down. Trial and error works.To me, on a street engine the worst problem of a wide sweep is excessive stem side load and severe guide wear.
Woody

blykins

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Re: Valve Stem Wear Signature
« Reply #13 on: January 02, 2019, 07:55:35 AM »
The drip tins were only ~ .015" thick.  They won't change the pattern much.
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
Instagram:  brentlykinsmotorsports
YouTube:  Lykins Motorsports