Technical Roller Rocker Carnage

Pulled the rocker arms off today since there was a little dried RTV hanging out and the bottoms of some of the rockers have some damage. I rebuilt the engine and reused the rockers and I don’t remember this, but that doesn’t mean it wasn’t there before. Any danger in reusing these? If it was a clearance issue I would assume I would see it on all the arm. Any ideas?

 

I see one rocker with damage by a pushrod that jumped out of place. Should be ok

 

Aluminum rocker are bulky and take lots of room. I prefer stainless steel.

 

Same here. I use steel roller rockers.

 

"Room" should not be a problem. Who cares about rockers taking up a little space..!
If the rocker with the bad spot, if the cup is in very good, non-damaged condition, it should be fine to use as is. If the cup has any marks down in the radius, then I'm not sure I'd use it if the mark cannot be polished out.
You need to find the cause of this damage, before you go too far. Check the roller tips and the fulcrum for smooth movement, and reuse if all are in good condition.

Like the others, I've use both Comp Cams and Crower Stainless Steel rockers on the street for years with no damage.

Mike

 

It would appear that the rockers are too low and make contact with the mounting stud base.
Im not sure if a longer pushrod would raise the rocker enough or just move the rubbing to a new location.

 

I looked at the picture close, and other than what appears to be some interference scruffs on the inside of the bottom row rockers (and of course the obvious one), I can't see anything that jumps out. Personally I would inspect how far down on the rocker stud the rocker body is going to see if during motion they are touching the stud, and if so, gently clearance the rockers.
Otherwise, if the trunions are smooth and you cannot feel or hear any grinding when rotated between your fingers, oil them up and reinstall.

 

Longer push rods for the bottom damage. Damage on the roller side is from too big of a diameter spring. Need to check at 50% lift for good geometry.

 

I agree about the need for longer push rods. Any chance the engine has aftermarket aluminum heads, with a lot of them .100 longer p/r’s are called for. You should check the rocker arm sweep on the valve tips.

 

Looks like some of them were hitting the top of the stud towers.

 

Adding guide plates will cause that problem if the stud bosses are not milled down a bit.....

 

https://www.enginebuildermag.com/2011/01/selecting-the-right-high-performance-rocker-arms/
Interesting article, for me at least. The part about anodized rockers being 50%weaker than those not, because of the anodizing process, was particularly interesting.

 

Longer pushrods aren't the answer, and can create other issues. Correct pushrod length is critical to ensuring the rocker tip rides centered on the valve stem. Add a longer pushrod and you'll end up with the tip riding off center, and then you've really got problems!

 

I agree 1971BB427 but with the look of these rockers we are not needing much maybe .010-.020” which would work for him.
I spend a lot of time on rocker geometry and use many parts for the proper solution. Your typical guy doesn’t know about valve keepers with different heights, the use of lash caps, especially on 10* keepers, beehive tops and retainers, and of course pushrod length etc. I personally have given up on stud mounted rockers and have gone to T&D sportsman and never looked back. No more stud girdles, poly locks etc. and the cost is very little more. A season or racing and no valve clearance adjustment sold me.

 

I did not suggest longer push rods as a wholesale change, I’m wondering if the engine has aftermarket aluminum heads that in some cases call for +.100 p/r’s.
Hopefully when @isan42 gets back online we can get some more details about his combination.

 

Sorry everyone, didn’t get email notifications like I thought I would.

Engine is a SBC with double hump heads. I do have guide plates, and I did check the pushrod length and order custom length pushrods, but I could have messed up, since it was my first time doing it.

So, since it’s likely the guide plates are pushing up the base of the stud too far, what’s my best (cheapest) solution? It’s not a high RPM engine (144 blower) so I don’t really need the roller rockers, it’s just what was on the engine when I inherited the car.

 

If your heads had guide plates from the factory then the base of the studs would not be too high. That could only be a possibility if screw-in studs and guide plates were added to the heads and the stud bosses were not milled enough. Can you give us the casting number on the heads and also the length of the push rods you ordered? Stock SBC p/r’s are 7.800 for a flat tappet cam.

 

Can grab the castings later today but the guide plates are aftermarket.

looks like I did order the stock length pushrods (pn. 249-7812-16)

so, I need to recheck the pushrod length? I want the roller to wipe in the middle of the valve stem, correct? I do have a adjustable length pushrod

 

Correct pushrod length does not necessarily put the roller tip contact centered on the valve tip....centered is a secondary consideration that while nice is not a requirement. Most important is narrow sweep width of the contact pattern, even if it is off-center.
On center but wide sweep will eat the valve guides right out of it, since wide sweep side loads the valve into the guide wall harder.
So many guys have repeated that completely wrong "center the contact on the tip using pushrod length" mantra for so long it has become an entrenched "fake news" fact. Magazines and even some clueless cam companies parroting it around certainly didn't help either.

Want to do it right use the Mid-Lift method.
Push Rod Geometry for Engines - YouTube

 

I used the above method to check for pushrod length and it came out to .200 longer. I did the typical sharpie on the valve stem to check, does this look ok?

 

Having the pattern more in the center would be ideal.....


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In my mind I picture the mechanical operation of a roller rocker arm pushing against a valve stem, and the logical ideal is pushing down dead center will produce less sideways force......but then there is the discussion about the width of the sweeping motion. If someone were pushing straight down on a valve, it probably doesn't matter much if they are on center or not.....no sideways force. So the idea is that by getting the sweep to be very narrow, someone is essentially pushing straight down. Now my mind is picturing the relationship between the rocker and the tip, and the only way I can see that narrow band happening is by having the rocker arm much higher than normal......which would change the actual mechanical ratio of the arm. I don't see any way possible for it to narrow the sweep and maintain the original ratio. Also, rollers are going to negate most of the sideways force on a valve anyway.
If someone has stamped steel rockers and they get them below the optimal pivot point, they are probably generating a lot of side force and wearing guides. Now I'm not saying that the stuff I just said is correct........but it just seems logical....at least to me.

 

The amount off center could be lived with....its about as far out as I couild let pass in search of the narrowest sweep pattern....but I don't like how close the top of the keepers and retainer are t the valve tip.
This set-up really screams for a set of lash caps and the correct keepers to fit them in. Adds a little height to the stem, getting the rocker a little more width on the stem tip to work with and proventing possible contat with ather parts of the retainer/keepers package.

 

I noticed that the stud bosses were milled down, but for what "thickness" guide plates?????.......

 

Looks to me that the roller end could be hitting the retainer. Valve stem heights look low to me.


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