S/B rocker arm geometry and contact patch

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rumblefish360

rumblefish360

I have escaped the EVIL Empire State!
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I have Comp Magnum roller rockers on top of Edelbrcok RPM heads and a Comp Solid cam. (248/.525) When I run the engine around for the contact patch on the valve stem top, the wear mark starts right about the middle (barest of margin above at best) and runs towards the exhaust side of the valve tip.

If I'm correct, the 2 ways to adjust this contact patch is drop the rockers bar down or lash caps in order to move the contact patch into the middle of the valve stem tip?

Push rods have yet to be made up. I have an adjustable one now to help with that.
 
lash caps.
measure lobe lift and compare it to the actual lift measured at the retainer with your rocker ratio figured in.

might not be as bad as you think.

post a pic.
 
Rob, see if you can post a picture that shows the contact pattern after a full valve closed/open/closed cycle. You're not running a crazy lift cam so the exhaust side valve stem contact might not be that bad. Is the contact pattern showing rocker in center of valve stem at full open?
 
Lash caps may be in order but just how far off is this? This obviously isn't going to be an 8000 RPM engine so if it's just a little off I'd say it's no big deal.
 
1W&C, the actaul lift after las was .510. That would be .007 more. However. I can not keep the dial indicator from rocking around since the engine is (Gasp) suspended. I know X 3, not good.

Demonseed, Terry, I'mmm, I think so, I didn't take a picture, BRB for one. I thought I had one. Alot of pictures were extremely dark and deleated since I could not get them to look better with the computer program.

Guitar, LOL, yea, power should be done by 6000 or so.
I didn't think it to bad myself, but, I figure I'd try as best as I could. Below are the pictures showing the patch. This is the second rocker I tried it on. The first one showed better, but, again, I couldn't get a good picture of it.

You can see, it starts in the middle preety much if not ever so slightly towards the intake side, as so seen by less than half a semi circle, and rolls exhaust side some. The bottom 2 shots are on the base circle of the cam, valve closed.

Otherwise, at mid lift, the rocker arm and pushrod look like one straight line. This is what I'm told I want. (hughes engines)

100_1103.jpg


100_1106.jpg


100_1107.jpg
 
1st Rocker tip alignment, valve closed

2nd Rocker tip alignment valve open/max lift

3rd side shot of valve tip valve open at max lift

4th, closer shot.

What do you all think about that?

100_1113.jpg


100_1115.jpg


100_1118.jpg


Copy of 100_1118.jpg
 
If you use lash caps you will probably need new retainers/locks to make them fit. My current setup won’t work with lash caps because there is not enough clearance on top of the valve for them.

BTW, I also have eddy heads, Comp pro mag rockers, and a comp solid roller.
 
Did you have a valve job done on these? At mid lift the rocker should be centered on the stem. It's not tremendously bad but I'd be unhappy with the sweep as it currently is.
 
rumble, it seems you may need slight longer pushods, that is that you have more lift than you should and when i look at the pic it looks like you are just over the 90* with the push rod/rocker body.jmo
If I'm awake enough, I believe it's too long a PR nets you less lift and vise versa.
It looks like it will live but it right at the edge, as in a lil more to the exh side than desired max.

True lash caps will most likely need comp #740-16 retainers locks with 10* super locks w/ lash cap#612-16 recesses AND then all you'll need is enough stem distance from the lock grooves.

I'll snap some pics of my similar sitch.fwiw.

Even funnier is that no one came in and said it was the rockers fault like some did on my geometry thread all because I didn't have their favorite brand of rockers.lol
 
moper said:
Did you have a valve job done on these? At mid lift the rocker should be centered on the stem. It's not tremendously bad but I'd be unhappy with the sweep as it currently is.
Click to expand...

A valve job would have helped him with this sitch.
then the stem would have been raised up .
 
Rob, your valve stem contact pattern looks close but as Moper says it ain't close enough. You may want to consider having the rocker shaft pedestals machined to truly fix the problem. I'm guessing .010" which shouldn't greatly impact your push rod to adjuster screw being on center.
 
flyfish said:
If you use lash caps you will probably need new retainers/locks to make them fit. My current setup won’t work with lash caps because there is not enough clearance on top of the valve for them.

BTW, I also have eddy heads, Comp pro mag rockers, and a comp solid roller.
Click to expand...
My cam is a solid and the rockers "Magnum" from comp. There a bit old with very little miles. ;0
I'm not going that route then if I have to go through all of that for lash caps. To much at this point.

moper said:
Did you have a valve job done on these? At mid lift the rocker should be centered on the stem. It's not tremendously bad but I'd be unhappy with the sweep as it currently is.
Click to expand...
No valve job. At mid lift, the rocker is slightly off center. I'm also not unhappy, just looking to do the best with what I got.

demon seed said:
Rob, your valve stem contact pattern looks close but as Moper says it ain't close enough. You may want to consider having the rocker shaft pedestals machined to truly fix the problem. I'm guessing .010" which shouldn't greatly impact your push rod to adjuster screw being on center.
Click to expand...

Well, machining the stands was mentioned in another thread I dug up.
http://www.forabodiesonly.com/mopar/showthread.php?t=53890&highlight=rocker+geometry
And at the Hughes engines site they also mentioned machining the stands downwards as well I think. Between the two, IDK. I'm just simplyout of money for this. I'm going to have to ethier make due or not finish up.

It was machine the stands or lash caps .

It looks live-able?

1wild&crazyguy said:
rumble, it seems you may need slight longer pushods, that is that you have more lift than you should and when i look at the pic it looks like you are just over the 90* with the push rod/rocker body.jmo
Click to expand...

The lash is a little lose. I can tighten it up with the pushrod. It's a checker pushrod. Lash is .022. When I got tired and had enuff for the night, the feeler gauge wasn't draging through so much.

Being tired and looking foward to a nights work which wasn't but a few hours away, I thew in the towel for the night and ....here I am.

I think I can squeeze out another .002 - .004 out of the lash. I'll try in a few.

Whatcha all think, about good to go? Even more so if I can back it up, the contact marks on the tip.
 
I'm thinking Rob that considering you're not running dual springs or a crazy lift cam that there is one other thing you can do. First though you need to find out how much needs to be machined off the pedestals. Get yourself an old rocker shaft and cut the end off the shaft leaving the short end with just 2 hold down holes. Then have a machinist offset machine the bottom of the shaft just at the area that contacts the pedestal .010". Bolt the short chunk to the 2 pedestals and now see what your contact pattern looks like with shaft being .010" closer to the head, this will give you an idea how much more if any would have to come off. Make sure you check the rocker chin to retainer for good clearance. See where I'm going with this. If .010" does the trick purchase 2 heavy wall rocker shafts, if you don't have them already.
 
now you're talking more money than $30 and $45 retainers + time.

Here's a look at my wear pattern with the not perfect geometry I have.
the pic is not great since my cannon is not a good detailed 'close up' camera.

IMG_0792.jpg
 
No spare junk shafts. Only another hardened chrome set. I see where your going.

1W&C, patch is good. I see where not perfect comes in, but it looks preety darn good.

OK, off to re-play with pushrod length. A teny tiny more length..........

OH, on the picture, just pull away farther. Then, after downloading it, in the picture adjustment section of whatever program you have, just magnifiy the shot and then crop it. I myself use Microsoft picture manager.
 
The problem is the stems are too high already IMO looking at it. Raising the shaft in this instance (with the pattern only moving outward on the stem as it gets moves and not coming back accross the stem) will move the pattern further out. As the stem gets taller (like if the valves are sunk) it gets closer to the shaft centerline. It looks like it needs to be shorter and the pushrod will need to be longer. You're basically looking at whatever pushrod fits giving proper preload and thread engagement in the rocker body. Otherwise pushrods dont affect geometry on a shaft system.

Edited - pic shows healthy sweap. It starts on intake side, going accross to center at mid lift, then slightly back at full lift. The rocker tip should make a small arc and mid lift is the center of the arc, so the tip should be centered on the valve stem at that point. Least that's how I learned it.

100_1843.jpg
 
I think the roller tip is supposed to roll to the outside from the center, could be wrong but I have a book at the shop from one of the best pro stock engine builders around and will look tomorrow. I had to shim my shafts way up around .045 ish and never wore the valve guides out again.
 
1wild&crazyguy said:
rumble, it seems you may need slight longer pushods, that is that you have more lift than you should and when i look at the pic it looks like you are just over the 90* with the push rod/rocker body.jmo
If I'm awake enough, I believe it's too long a PR nets you less lift and vise versa.
It looks like it will live but it right at the edge, as in a lil more to the exh side than desired max.

True lash caps will most likely need comp #740-16 retainers locks with 10* super locks w/ lash cap#612-16 recesses AND then all you'll need is enough stem distance from the lock grooves.

I'll snap some pics of my similar sitch.fwiw.

Even funnier is that no one came in and said it was the rockers fault like some did on my geometry thread all because I didn't have their favorite brand of rockers.lol
Click to expand...

true i have the same set up i ended up with push rods that were .050 longer than stock worked perfectly
 
moper said:
The problem is the stems are too high already IMO looking at it. Raising the shaft in this instance (with the pattern only moving outward on the stem as it gets moves and not coming back accross the stem) will move the pattern further out.
Click to expand...

I see. Thats where droping the shafts/lowering the stems comes in. Gotcha.



As the stem gets taller (like if the valves are sunk) it gets closer to the shaft centerline. It looks like it needs to be shorter and the pushrod will need to be longer. You're basically looking at whatever pushrod fits giving proper preload and thread engagement in the rocker body. Otherwise pushrods dont affect geometry on a shaft system.
Click to expand...

And after adjusting the pushrod spining this engine around a few times to the "Rubber arm" point, I agree.

Edited - pic shows healthy sweap. It starts on intake side, going accross to center at mid lift, then slightly back at full lift. The rocker tip should make a small arc and mid lift is the center of the arc, so the tip should be centered on the valve stem at that point. Least that's how I learned it.
Click to expand...
My current contact patch is really close to what you have. Thanks for the picture.


the67fish said:
I think the roller tip is supposed to roll to the outside from the center, could be wrong but I have a book at the shop from one of the best pro stock engine builders around and will look tomorrow. I had to shim my shafts way up around .045 ish and never wore the valve guides out again.
Click to expand...

I went to Hughesengines and Comp Cams and read up. That's the best I got.

Guitar Jones said:
I don't think it's terrible and is probably very livable with your combo.
Click to expand...

I agree. I'm not so worried about catastrophic failure, just long term abuse. Though, I doubt the cam will be in there to long. My intail plan was a different cam and ported heads, but, I am making due with what I have for now. I'm not thrilled, but just simply OK with it.

I took out the digital mic (With the Kodak) and tried to measure up the distances.

Valve stem top approx. .028 until the bevel.
Top shaded area of the valve stem approx. .1190
Bottom shaded area approx. .0625
roller tip swipe area approx. .0985

Thanks for the help everybody. I think I'll be taking that engine to the bay soon. A few days after a quick clean up of the engine bay.

100_1121.jpg


100_1141.jpg
 
remember... the rocker at 90 w/shaft is as far as it's gonna sweep outward.
which is why raising the stem height actually pulls the roller tip back toward the intake being it's above its furthest outward sweep. just a thought.
but hey... however you fix, as long as its fixed.
 
moper said:
The problem is the stems are too high already IMO looking at it. Raising the shaft in this instance (with the pattern only moving outward on the stem as it gets moves and not coming back accross the stem) will move the pattern further out. As the stem gets taller (like if the valves are sunk) it gets closer to the shaft centerline. It looks like it needs to be shorter and the pushrod will need to be longer. You're basically looking at whatever pushrod fits giving proper preload and thread engagement in the rocker body. Otherwise pushrods dont affect geometry on a shaft system.

Edited - pic shows healthy sweap. It starts on intake side, going accross to center at mid lift, then slightly back at full lift. The rocker tip should make a small arc and mid lift is the center of the arc, so the tip should be centered on the valve stem at that point. Least that's how I learned it.
Click to expand...

1wild&crazyguy said:
remember... the rocker at 90 w/shaft is as far as it's gonna sweep outward.
which is why raising the stem height actually pulls the roller tip back toward the intake being it's above its furthest outward sweep. just a thought.
but hey... however you fix, as long as its fixed.
Click to expand...

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