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Author Topic: 289 with off-center rocker arm... what's next?  (Read 5263 times)
hawgdriver
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« on: June 10, 2014, 11:32:06 pm »

I was in the process of replacing my header gaskets this weekend to fix an exhaust leak and decided to remove the valve covers to replace that gasket as well (my 68 Stang had been in storage for several years before it's recent awakening).  I was surprised to see one of the rocker arms canted to the side and barely touching the valve stem (pictures attached).

Knowing that this is not that uncommon and the fact that I caught the problem before any catastrophic damage occured, I'm now trying to figure out what to do in order to fix it without breaking the bank.  I realize the press-in stud is shot, the push rod is bent and the guide slot is worn, the rocker arm is toast, and the valve stem is no longer square.  However, I'm hopeful that there's a chance I can fix this without taking the heads to a machine shop, but am also realistic that this is not likely.  Is this problem going to require a mod to all 16 valves, rocker arms, guide slots, studs, etc; or can I just fix the one problem?

A little more info about my '68 Stang which is purely a weekend driver:
  • Roughly 5k miles since the 289 was rebuilt in '98 (by my Dad and I... mainly my Dad.  It has been in long-term storage for the past 15 years or so  Sad ... a tragedy I know)
  • Stock heads and components (other than whats listed here)
  • Edelprock Performer intake, mild cam (I don't know the specs), and 600cfm carb
  • Headers (Hooker if I recall correctly)



* offCenterRocker.JPG (297.14 KB, 1024x768 - viewed 443 times.)

* wornStudAndGuideSlot.jpg (310.15 KB, 768x1024 - viewed 392 times.)

* wornRocker.jpg (227.98 KB, 768x1024 - viewed 341 times.)

* bentPushRod.jpg (241.02 KB, 1024x768 - viewed 379 times.)
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scienceguy
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« Reply #1 on: June 11, 2014, 12:30:50 am »

Does that stud have a groove cut into it by the rocker?  It looks like it.  The rocker had a side load on it for whatever reason, and ate into the stud...  eventually gnawing its way through until it was off to the side like that.  Looks like the pushrod is bent as well.

You're probably going to need to remove the heads to repair the studs.  You might get by with pulling the one that is damaged and pound another one in there, though.  At minimum, you're going to need a new pushrod, rocker and stud pressed into place.  Some might use this as an excuse to install a nice set of aftermarket heads and rockers.  Smiley

Good Luck!
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1966 Mustang, Toploader 4-speed
Pump Gas, Flat Tappet 306
9.88 @ 135.67
D Staff
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« Reply #2 on: June 11, 2014, 12:35:47 am »

I'm guessing that if you started removing the other rockers, you would find more guide slots are starting to wear other than just that one. The only "correct" fix is to remove the heads and have them machined for screw-in studs and guide plates. If your machinist is like me, you will also likely be told the heads should be completely gone through and rebuilt.

 Good Luck!
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juiced coupe
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« Reply #3 on: June 11, 2014, 12:44:32 am »

Those aren't 68' heads. They have close tolerance pushrod holes, which ended in mid 66.

It looks like those are mismatched rockers, some are rail design. That would explain the side loading and wear in the pushrod slot. The wear is going to take some machine work and new parts to repair.
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Doing more with less, or something like that.
http://sbftech.com/index.php/topic,20009.0.html

Quote from: Monte Smith
Bottom line, if it was the hot ticket, the fast guys would do it.............they don't

You might need some Titanium rods and a flow bench!  LMAO on floor

I honestly don't get it.

I'm sweating, my heart is racing, my clutch foot is twichin', and my right arm punched the computer screen doing an involentary 2-3 shift while reading all that. 
hawgdriver
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« Reply #4 on: June 11, 2014, 12:51:34 am »

Thanks for the quick feedback!  The stud is worn on the one side and it will definitely need replaced.  I was thinking I could do what scienceguy mentioned and replace the stud with another press in one, and then replace the rocker and pushrod.  I'm not sure what to do about the guide slot... Would I be crazy to leave it "as is"?

D Staff, I've inspected the other guide slots the best I could without removing the other rockers and they seem to be all good (at least on the one side).  I agree that a full rework is the correct way to go, but if I was to spend that money at the machine shop, would I be better off just replacing them with new/better heads than trying to salvage these?
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hawgdriver
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« Reply #5 on: June 11, 2014, 01:08:28 am »

Juiced Coupe, I guess that would explain the "66" stamped on the head Smiley  I guess the engine is not the original, other than the fact that the original had a 289 also.  How would I tell if it had mismatched rockers?  What would differentiate that it is a rail rocker (I admit I'm new to all this, but I'm learning fast)?  Thanks again.
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juiced coupe
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« Reply #6 on: June 11, 2014, 01:41:46 am »

Rail rockers have guides at the valve tip to align the rocker, along with round holes at the pushrods. Earlier rockers have smooth pads at the valve tips and use the close tolerance pushrod slots to guide the rocker. They can't be used together.
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Doing more with less, or something like that.
http://sbftech.com/index.php/topic,20009.0.html

Quote from: Monte Smith
Bottom line, if it was the hot ticket, the fast guys would do it.............they don't

You might need some Titanium rods and a flow bench!  LMAO on floor

I honestly don't get it.

I'm sweating, my heart is racing, my clutch foot is twichin', and my right arm punched the computer screen doing an involentary 2-3 shift while reading all that. 
scienceguy
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« Reply #7 on: June 11, 2014, 08:23:33 am »

Juiced, those are NOT rail rockers.  If they were, it would explain what was going on, but they aren't.  They are the correct rockers for the application.

That being said, you will need to inspect the other studs for damage.  There's a  really good chance that a number of them will show the same wear...   just not quite as bad yet. 

Full roller rockers don't pivot on a ball, and don't have an edge that can gouge into the stud.  You may be able to get by with replacing whatever studs are bad, and installing roller rockers for good measure.  Once you pull the heads and start going through them...  machine for screw-in studs, guide plates, surface, new valves, valve job, keepers, retainers, springs, valve guides, check for cracks, cleaning, etc... you're really close to a set of decent aftermarket heads that will run circles around the stockers.  If I had to pull them, I would simply replace them.

If you don't have much money to spend right now, I would see about a quick repair on the existing heads.  If you can scrape together the funds, any money spend repairing this damage could be put towards some new stuff.  Stay away from the Chinese stuff.  It's JUNK, with bad machine work and cheap, crappy hardware.  Edelbrock has some heads that won't break the bank too bad, and will work really well on your car.  Do a good install, check rocker geometry, and you should be good to go!

Good Luck!
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1966 Mustang, Toploader 4-speed
Pump Gas, Flat Tappet 306
9.88 @ 135.67
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