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Discussion Starter #1
My friend is running Crane Gold roller rockers on his 468. The engine has been together about 8 months. He has heard a slight clicking noise at idle and started to investigate by taking off a valve cover to check the push rod length. In the process, he noticed that the inside of the roller rockers, where the mounting stud comes through, is missing some material. In the photo below, you can see that some of the gold color (and material) has worn away.




We know that the pushrod length is longer than it should be from marking the top of the valves stem and seeing the pattern after a couple of engine revolutions.

Any ideas on what could be causing this?
 

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Does the condition exist on all rockers and both inner faces of all the rockers? Meaning, are both inner sides of the rockers worn?

Also, can you 'feel' the difference or is it simply the coating that has worn off?

Is there any side to side play of the rocker body on the trunnion? I'm wondering if the rocker body is maybe wandering side to side.

I personally would manually rotate the engine and watch the valve train through a few cycles.

Lots to consider with valve train geometry.

Question, why was it decided to run with incorrect push rods instead of getting the right lengths?
 

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This is just a guess, but if the guide plates weren't properly aligned I could imagine that happening. Its pretty easy on a BBC to twist a guide plate while tightening the rocker studs. When that happens the rocker tip ends up running off to one side of the valve tip. With all of the crazy angles involved in the valvetrain of a big block, it could load the rocker at an odd angle. I really doubt pushrod length caused that wear pattern.
 

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Discussion Starter #4
Does the condition exist on all rockers and both inner faces of all the rockers? Meaning, are both inner sides of the rockers worn?

Also, can you 'feel' the difference or is it simply the coating that has worn off?

Is there any side to side play of the rocker body on the trunnion? I'm wondering if the rocker body is maybe wandering side to side.

I personally would manually rotate the engine and watch the valve train through a few cycles.

Lots to consider with valve train geometry.

Question, why was it decided to run with incorrect push rods instead of getting the right lengths?
D_B,

Go to "My Corvette Photos" and look at this same pic there, blown up, and you'll be able to see that it's much more than the coating that's gone.

This engine is in New York and I've only seen a few photos, the one I've posted and a second one in "My Corvettes Photos". It looks like it's only on the one side, but I'm only getting that from the photo posted above.

Your idea about rotating the engine with the valve covers off is a good one.

I've the engine's owner to read this thread and give some more info based on your questions.

Thanks for the help.
 

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This is just a guess, but if the guide plates weren't properly aligned I could imagine that happening. Its pretty easy on a BBC to twist a guide plate while tightening the rocker studs. When that happens the rocker tip ends up running off to one side of the valve tip. With all of the crazy angles involved in the valvetrain of a big block, it could load the rocker at an odd angle. I really doubt pushrod length caused that wear pattern.

:agree: The push rod length is not going to be the culprit. However, if they are not right this is the best time to get them replaced by the right part.

Have your friend inspect the push rods. Even hardened rods...which are used with guide plates, will show wear if a misalignment of the plates is side loading the rockers. Both the rods and plates should show wear.

It's also important to find out if this is isolated to the one rocker or if they are all worn the same way.
 

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Hey Fred Man I have that same problem with my small block and it has screw-in studs with roller rockers and I think it's either #4 or #6 exhaust on mine that is doing the same as yours. I had Proforms on there before and then switched to Harland Sharps and still mine rubs just a little, but nothing serious has occured and I have no issues so I just left them alone. Sometimes when a boss is tapped it's not tapped just perfect and that may have occured on both yours and mine.
 

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This is just a guess, but if the guide plates weren't properly aligned I could imagine that happening. Its pretty easy on a BBC to twist a guide plate while tightening the rocker studs. When that happens the rocker tip ends up running off to one side of the valve tip. With all of the crazy angles involved in the valvetrain of a big block, it could load the rocker at an odd angle. I really doubt pushrod length caused that wear pattern.
:thumbsup:

He needs to check the sweep pattern on all the rockers
 

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Discussion Starter #8
Well, the answer seems to be that the trunion bearings are shot on the roller rockers. Nothing else would allow the movement that the rocker body is doing based on the wear pattern. We figured that the rockers have 40 to 50K miles on them. For the moment, by buddy put the factory stamped steel rockers back on, until he finds out if the rockers can be rebuilt. These are Crane rockers and they went out of business, but then were bought by S&S and are back with a partial product line. Probably go with new Comp Cams steel roller rockers.

Thanks for all the help.

Anyone notice the thin heads on the polylocks? I had them surface ground to fit under the factory steel valve covers.
 

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Well, the answer seems to be that the trunion bearings are shot on the roller rockers. Nothing else would allow the movement that the rocker body is doing based on the wear pattern. We figured that the rockers have 40 to 50K miles on them. For the moment, by buddy put the factory stamped steel rockers back on, until he finds out if the rockers can be rebuilt. These are Crane rockers and they went out of business, but then were bought by S&S and are back with a partial product line. Probably go with new Comp Cams steel roller rockers.

Thanks for all the help.

Anyone notice the thin heads on the polylocks? I had them surface ground to fit under the factory steel valve covers.

Good to know

I'll avoid Crane Rockers in the future as well as Harland Sharps

Thanks :nuts:
 

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Well, the answer seems to be that the trunion bearings are shot on the roller rockers. Nothing else would allow the movement that the rocker body is doing based on the wear pattern. We figured that the rockers have 40 to 50K miles on them. For the moment, by buddy put the factory stamped steel rockers back on, until he finds out if the rockers can be rebuilt. These are Crane rockers and they went out of business, but then were bought by S&S and are back with a partial product line. Probably go with new Comp Cams steel roller rockers.

Thanks for all the help.

Anyone notice the thin heads on the polylocks? I had them surface ground to fit under the factory steel valve covers.

Comp Magnums are a great value. Fantastic quality and affordable price.

Question, as I did the same thing...What was the thought behind milling down the heads of the poly locks instead of the base?

As long as it's done on a lathe or mill for precision, the base is a better option. I removed a full .25" from my poly locks by milling off at the bottom. I filed and sanded them smooth, and chased the threads. They fit under the valve covers and I have full heads on the poly locks.

Something to maybe think about, as poly locks are cheap and easy to get. Heck I have a few extra sets I'll donate if you ever need to do it again.
 

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Discussion Starter #11
Good to know

I'll avoid Crane Rockers in the future as well as Harland Sharps

Thanks :nuts:
I don't know anything about Harland Sharp rockers, but I don't think either brand is meant to go so long without a rebuild. These rockers were on my 427 and then on Dan's 427 and now on this 468. The surface grinding I mentioned above was done in 1995, so there's a lot of miles on the rockers since then. Plently of 6500 rpm rips.

One thing I learned was that a steel rocker is stronger, so for the same size profile at the trunion, you need less material for the same strength so there is more volume available for a bigger bearing/axle set-up. My Comp Cams stainless steel rockers have larger bearings and are definitely rebuildable.
 

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Discussion Starter #12
Comp Magnums are a great value. Fantastic quality and affordable price.

Question, as I did the same thing...What was the thought behind milling down the heads of the poly locks instead of the base?

As long as it's done on a lathe or mill for precision, the base is a better option. I removed a full .25" from my poly locks by milling off at the bottom. I filed and sanded them smooth, and chased the threads. They fit under the valve covers and I have full heads on the poly locks.

Something to maybe think about, as poly locks are cheap and easy to get. Heck I have a few extra sets I'll donate if you ever need to do it again.
D_B,

I chose to surface grind the heads of the polylocks, because I wouldn't be changing anything regarding the relationship between the polylock and the roller rocker. The set screws are so far down the hole that their thread engagement wasn't affected at all. If I cut them shorter than necessary from the bottom of the polylock, then the hex head could get too close to the top of the rocker, to the point of interference. When grinding from the head side, I didn't have to be exact with the final length, just leave enough hex head to work.

I was doing it just for clearance with the stock valve covers, when I was running the tri-power, AIR pump and all the stock jazz. Now I have tall valve covers, a single 4 barrel and Edelbrock Air Gap manifold, Hooker side pipes, etc, so it's not looking too stock these days.
 

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Discussion Starter #15
Are you sure that your studs are not bending ? What type /force of valve springs are you using ? Lift of the cam ?
The heads are GMPP 290cc oval ports with 7/16" screw-in studs. These heads are made by Edelbrock and use the stock valve train geometry (meaning less problems than with Dart, World Products or other aftermarket heads with non-stock geometry). The cam is a Comp XE274H, hydraulic flat tappet with 274/280 advertized duration (230/236 @ 0.050" lift). Valve lift is 0.552"/0.555". Nothing radical. 6000 rpm redline with this cam. Springs are 130# closed and about 360# open. The heads were just redone by a professional. He didn't have the rockers at the time of the rebuild and didn't see them until yesterday morning.
 

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I'm with Belgian1979 cause if the studs aren't tapped straight or if the stud is bent then the rocker will be off. I know cause that is what happened to mine and I know because two different companies (Harland Sharp and Proform) have been on mine and the same one rubs so that is the problem. Harland Sharp is a very well know company and Proform is what GMPP use to use ( not sure if they do now). I've had Comp Cams guideplates that were made for 5/16 pushrods not even be close to their demisions cause I had to open the hell out of them so my pushrod would fit in the guideplates. My whole point is that Crane use to be good and any part from any manufacture is suspectible to problems. Good luck and I hope you find your problem and sorry for the long reply:thumbsup:
 

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Fred have you determined if it was just the one rocker with the wear or did they all exhibit it?
 

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Discussion Starter #18
Guys,

You have to remember this isn't my engine and it's in NY and I'm in Florida. I've seen a few more pictures than you have, one or two of one cylinder head and the No. 1 valve stems. I wanted the engine's owner to put this to bed, by disassembling a rocker or two. It's only a snap ring holding the works together, but so far that hasn't been done.

I have had some of the weirdest and worst luck with some of the things I have and/or others have done on the various versions of my engine and other components. When something is going wrong, I want to find out why. So I'm not satisfied that we know what's going on here, but for the moment, the owner has put the stock stamped rockers on and buttoned the engine up in order to be able to move it. How far he'll look further into this I don't know.

The heads were just gone through, but the builder only worked on the heads and didn't assemble the engine. So the heads could've looked fine on their own, but could have something wrong once assembled on the block with the topworks in place. From the marks on the underside of the one rocker you can see, there had to be quite a bit of misalignment between the rocker and stud to cause the damage. If the stud bent that much to cause what can be seen, I think it would have broken or the pushrod would have bent if the rocker was not worn. I don't know if the pushrods were checked for straightness.

There's only so much one can do with a limited amount of information. Again, thanks for the input and suggestions. That's what makes DC a great place. If I hear more on this subject, I'll report back.
 

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Discussion Starter #20
I'm with Belgian1979 cause if the studs aren't tapped straight or if the stud is bent then the rocker will be off. I know cause that is what happened to mine and I know because two different companies (Harland Sharp and Proform) have been on mine and the same one rubs so that is the problem. Harland Sharp is a very well know company and Proform is what GMPP use to use ( not sure if they do now). I've had Comp Cams guideplates that were made for 5/16 pushrods not even be close to their demisions cause I had to open the hell out of them so my pushrod would fit in the guideplates. My whole point is that Crane use to be good and any part from any manufacture is suspectible to problems. Good luck and I hope you find your problem and sorry for the long reply:thumbsup:
These GMPP heads have been on this car for more than 4 years without a problem. Then about 8 months ago the heads were switched over to a 468 short block with the roller rockers. So, I think the basic head, guide plates and studs and the basic geometry were sound up to that point. Of course, that could have changed in the case of a bent stud or something else recent.
 
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