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Lazy Rocker Arm

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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Topic: Lazy Rocker Arm
    Posted: Apr/13/2021 at 2:13am
Welcome to my latest drama, seems I have a lazy rocker arm that doesn't want to sit on the valve tip properly and would rather ride around on the retainer and lock.





I'm running stock rockers with Chev studs and polylocks to give me some adjustment. It seems the slot in the rocker is allowing the arm to tip over to the side and not run true on the valve tip, possibly contributed to by the fact that the valve tip now has some damage on it.

I'm not sure how long it's been running like this, but obviously long enough to cause a fair bit of wear, this is on the Gremlin drag car. I have tried replacing the rocker arm with another, but still have the same issue.

I realise I probably need to pull the head and repair or replace the valve, but only have a couple more meetings this season that I can run at and probably wouldn't get it back together before the end of the season so I'm looking for a temporary band aid solution, preferably so that I can run it this Friday night.

Couple of options come to mind:

1) Slap some roller rockers on it, the pivot shaft would hold the rocker upright and hopefully the valve and roller tip would survive. Not sure I can actually source a set of rockers in time for this.

2) Try running a factory stud in this position as the shoulder on the stud would help fill the slot in the rocker arm and prevent it tipping over.

3) Could I run a lash cap on this valve to give a wider and flatter surface for the rocker tip to run on. I'm not sure how a lash cap would sit on the valve tip rather than the lock as there is not a lot of valve tip projection to work with.

4) Call it a day and park it up for the season.            
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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 7:16am
Same issue, same valve on the other head, it’s the rear valve on the driver’s side, front valve on the passenger side.

Any suggestions on what the cause is?
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Heavy 488 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 7:32am
Pushrod bent or is the guide slot in the head worn out?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 8:05am
Agree with Heavy 488, but at this point the rocker has also worn on an angle and has to be replaced or the taper removed.
The head of the valve stem should also be checked for flatness. A washer sitting on the spring retainer, blue the end of the valve stem and use a piece of tool steel or similar to find the pattern on the valve stem. If it's convex, you can use the washer(s) and a fine stone to flatten the stem again without removing the valve.
If the valve stem sits below the spring retainer, there is a problem right from the get go. Wrong retainers, locks or both. A valve stem should always sit above the spring retainer on assembly. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 8:39am
I have had this problem in the identical situation and hardware. The slot in the head is likely worn, and with the non shouldered studs the rocker can and does wave all over the place. You should be able to fix with a set of guide plates. I have never used aftermarket guide plates on iron heads as this happened to me decades ago and they were not easily available. I took a set of stock BBC 5/16" guide plates (the ones everyone throws away) with the step up, and cut the center connecting strip out and used those. It took multiple tries the get then aligned with the studs TIGHT, but once correct they worked fine. Did not bother worrying about connecting the plates.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 9:07am
I'm wondering if the slots in the heads might be just enough out of alignment that the rocker can move far enough off center for it to tip over, may well be just worn as suggested, but seems specific to that particular slot on both heads. You can't push the rocker off the other side without considerable effort. 

You can actually see where the edge of the valve tip is worn at an angle roughly where there is also wear on the locks (retainer and locks had been off and back on by the time the picture was taken. The other side wasn't quite so bad.

Might just be another lesson learnt the hard way, I was only in there to swap out the valve springs because I thought they might be getting a bit tired, maybe I need to be checking things like this a bit more regularly. I've been turning it to +6,000 rpm, every run for about 180 trips down the strip.



Edited by WesternRed - Apr/13/2021 at 9:09am
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Steve_P View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 9:11am
I also vote worn slot in head- easy to confirm.  I needed guide plates decades ago, like Ken said, and used the Isky adjustable ones as there were no AMC ones at that time.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 10:18am
Short term solution to get trough Friday night is to put in larger diameter push rods or even sleeve the push rods on these valves to center the rocker. You take the small chance of retainers coming off the valve, but sometimes there are other things that take priority and you live with the risks.
I would not waste a roller tip rocker just for the weekend.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BassBoat Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 12:51pm
I had a friend who found a chunk broken out of the pushrod guide hole in the head.  Solution was to put a guide plate on.  I had some lying around and I gave him one.  

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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2021 at 5:55pm
After some testing, if I run the factory stud and stock pushrod I have about 0.025” lash at the valve tip, so if I run a slightly longer pushrod, I can use the factory stud and still have a bit of room for adjusting the preload. The raised collar on the factory stud should keep the rocker tip on the valve. That seems like the simplest solution. I have 8.100” pushrods in there now, which are probably way too long, just what I had laying around at the time.

Could also just run the correct length pushrod and not have or need any adjustment.


Edited by WesternRed - Apr/13/2021 at 6:00pm
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