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Bent Pushrod-Why? Addl Pics

DEL65

DEL65

Of The Morons
When I pulled my valve covers for the manifold swap, I noticed the rocker for exhaust valve #6 had slipped off. Stock 289 with no modifications. Don't know why it happened.

I pulled the rod and it's bent. I wonder why? All other rockers look OK. Can I just replace the rod, or do I need to replace the lifter too? Any advice? Do you need any other info? Thanks.

X007.jpg
 
Re: Bent Pushrod-Why?

Was the engine running? How badly bent?

The only reason I can think of for a push rod to bend is the valve not moving for some reason (???)
 
Re: Bent Pushrod-Why?

Same thing happened to me I replaced the heads because a couple valves where stuck a couple of my rods actually broke
 
Re: Bent Pushrod-Why?

Rocker arm fell off its mark on top of the valve stem. The cause? How about wear... i.e. the rocker arm. How about a valve guide that's excessively worn, cracked or otherwise so as to position the pushrod out of alignment on its end of the rocker.

Hydraulic or solid cam? Stick a good pushrod down on top of the lifter and manually crank the motor a revolution or two. Note the pushrod travel (without putting the rocker arm on) and compare vs. others.

Think about the other 15. Shoot up a picture of the underside of that #6 Exhaust Rocker... show us the wear. Maybe the hydraulic lifter could be busted collapsed etc too after this mishap... if that's the cam you have..
 
Re: Bent Pushrod-Why?

Yes - could be stuck valve but figure out what caused it. Also pull the plug out and look at the electrode and surrounding area just to see if it can reveal more information. Lastly if the valve is stuck you can install the rocker and begin to "load" it by threading it down on the valve tip so that the nut is at about the same threads down on the stud as the others... then back to manually turning the motor by hand until #6 exhaust valve and its cam begins to open the valve... if you feel the increase in force trying to spin the motor then it's valve is jammed. Expect the worst. I don't like the thought of crap in the cylinder and I would pull the head and again think about the whole deal.

Proceed with pulling off the intake since that's what you were doing initially... then you can see what's going on and look at the 15 other guys in there too.
 
Re: Bent Pushrod-Why?

are those rail rockers or conventional can not tell by the picture..maybe did you change over to more cam than stock.
"DEL65" said:
When I pulled my valve covers for the manifold swap, I noticed the rocker for exhaust valve #6 had slipped off. Stock 289 with no modifications. Don't know why it happened.

I pulled the rod and it's bent. I wonder why? All other rockers look OK. Can I just replace the rod, or do I need to replace the lifter too? Any advice? Do you need any other info? Thanks.

X007.jpg
Click to expand...


From the looks of the rocker arm it looks like you have conventional rockers...not sure why valve was bent is that the stock cam and did you have the lobes checked before manifold upgrade..maybe that lobe on the cam is worn and it messed up the mechanics and some how caused the pushrod to bend..was it a slight bent or was it noticeable running rough, did you check the valve springs they could get weak and cause walking of the rockers at high RPMs causing valve to hit piston and then bend your pushrod.should check valve stem also it coulkd be damaged...If you are doing any high RPM running need to go to guide plates and hardned push rods and that will fix your problem.. I would buy all new pushrods and find out for sure why you bent that one pushrod..
 
Thank you for all the responses. Bone stock 289 2v with about 105K original miles. The motor has never been apart.

Funny you should mention a stuck valve. Last summer I began to hear a slight 'tick-tick' noise up front; typical old lifter or exhaust leak sound. About 4-6 weeks ago, on a very cold morning, I tried to start the car, but the battery was dead. The motor turned over slowly a few times and died. After I replaced the battery, I started it, and for about 5 minutes I heard a loud ticking sound. I thought it was because of the cold weather and the oil was still thick. After the motor warmed up, the sound went away. I wonder of the valve stuck when the motor was cranking. I have not driven the car much since that day.

Here are some more pics. The top of the rocker looks OK. The inside shows rubbing marks. The rocker stud has some definite rubbing on the side. The lifter looks OK, but I'm not sure what a collapsed one looks like. While rotating the motor, I saw valve movement. It looked like it opened/closed OK.

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Re: Bent Pushrod-Why?

Your rocker stud and the rocker itself are damaged/enough galling to move the rocker off the valve tip. What I suspect you had is a lifter with bad internal springs that floated out of oil when sitting allowing for the ticking and also change in valve lash which in turn created the stresses you now see. The when the motor was cold the lifter itself was not sufficiently dampened (.i.e. more or less collapsed which in turn allowed the push road to fall out of its seat on the rocker... next few moves up by the cam resulted in the bent push rod. since you are taking off the intake see if you can remove the lifter and inspect. I would take this opportunity now to change timing chain and gears, maybe consider a new cam and lifter set and I would pay close attention to valve stems etc.

A quick fix for now is just replace the lifter, stud and worn components. But in the spring I would be rebuilding the valve train for sure and would do the heads while at it.
 
Re: Bent Pushrod-Why?

Short of a rebuild, at least pull the heads and have them gone through. I'm sure a combination of things contributed to the pushrod bending. What does 46 years of metal fatigue do to an engine? I'll bet there's a handfull of old umbrella oil seal fragments in your oil pan, indicating an oiling problem in the past. . .

Robert
 
Re: Bent Pushrod-Why?

"DAVER" said:
A quick fix for now is just replace the lifter, stud and worn components. But in the spring I would be rebuilding the valve train for sure and would do the heads while at it.
Click to expand...

The spring probably isn't the problem. But the tip of the valve is definately worn. The heads need to come off. At this age, I'll bet all the exhaust valves are sunk into the seats so far that they all need to be replaced.

Robert
 
Re: Bent Pushrod-Why?

lots of maybees such as the rocker stud could have given a little(pulled out of the head),nut holding rocker maybe needs replacing. i would just do the easy stuff first starting with double nut the rocker and try it and see. wes
 
Thanks again for all the input.

My long-term plan was to rebuild motor in late this year or early next year, so this problem comes a little too soon. I'm not sure that I want to spend any money on this motor or heads.

If I just replace the rocker and push rod, will that get me through this year? Too risky? I drive about 600-800 annually, including a 600 mile weekend road trip to Southern Calif.

Also, anyone have a rich aunt?
 
My quick assessment, if you want a QD fix:

Presuming the lifter/cam checks out OK....

That valve tip is likely going to give you trouble with the OEM scrubber rockers, so here's an idea.

Get one hardened pushrod; yes, I know you don't need it.
http://www.summitracing.com/parts/CCA-7935-1/

Get one roller rocker; doesn't have to be tricky or expensive. Example:
http://www.summitracing.com/parts/CRN-11746-1/?rtype=10

Stick everything together and see how the roller tip contacts the valve stem and where the fulcrum rides on the existing rocker stud. The roller rocker provides precise locating of the tip so you can see how far off the valve stem tip is. If it looks fixable, a flat file can work to flatten it. Since the roller rocker rolls instead of scrubbing and contacts just a small area, it's a bit more forgiving.

If you have to remove the stud (I wouldn't if there's less than .080" of wear in that slot *and* if the fulcrum captures it), you can stack some washers with a rocker fulcrum ball on top and use a hardened nut to pull the stud out, being careful not to bottom out the nut on the threads. The resulting hole is the right size for a 7/16-14 tap and the threads can be tapped with the head on, if you're careful to capture the shavings. I usually use grease and suck the mess out of the hole with the shop vac. If the hole is not blind (goes into water) use some Permatex #2 when putting the stud in. Be careful to tap the hole as perpendicular to the machined boss as possible. Use a stud something like this:
http://www.summitracing.com/parts/MRG-1076/?rtype=10

Check everything carefully and adjust valve lash to spec. Sounds like a lot of work but it really isn't. Shouldn't take more than an hour, plus reassembly.

IMO, if the engine ran fine before and the camshaft isn't damaged, I'd attempt this kind of repair before taking the heads off. The wild card is the valve stem tip. Hard to know without being there what we can get away with. I've fixed worse. There's always a way. Good luck

Pat
 
I would also add a lash cap to the damaged valve tip after smoothing it up with a small flat file. Make certain that the cap does not contact the valve keepers. (read that last sentence again). I'd start here: http://www.summitracing.com/parts/CRN-99421-2/

Ditto with the roller rocker, and add the thickness of the lash cap to the length of the new pushrod. You can buy custom length pushrods for cheap, about $12-20 each for a common app like a SBF.

Personally I would pull the heads, rebuild them, and install a new valve and stud, but if I was 800 miles from home, in a NAPA parking lot I'd fix it like that. If you only put 800 miles on it a year, and you are going to pull it and rebuild it in the fall, then same thing, right?
 
"66benchcoupe" said:
So you think the hole in the head for the pushrod is acceptable to use as a guideplate for the roller rocker?

Robert
Click to expand...

Apparently, CAMACHINIST does. The heads do not use the "rail" type rockers and the purpose of the hardened push rod CAMACHINIST recommended is to be able to take the rubbing that comes from the "slot" heads guiding the push rod.
 
Thanks again everyone for all the assistance. I'll let you know what happens. I'm not going to do much until this weekend.
 
"66benchcoupe" said:
So you think the hole in the head for the pushrod is acceptable to use as a guideplate for the roller rocker?

Robert
Click to expand...

From the photo of the bent pushrod, there doesn't appear to be abnormal wear in the guide area, so I'm presuming the cast-in guide slot is still serviceable. That said, a roller rocker is a bit more forgiving of a little slop than the ball/fulcrum rockers. Things can go sideways pretty fast with those.

My first thought was installing a lash cap, and that's a good idea if it will stay put with the damaged tip. I spec'd a longer pushrod to allow for the increased height, though geometry isn't critical with a stock cam and OEM engine, IMO.

Also, I like the hardened pushrods because of the material they're made out of and how the hardening affects the tensile strength. If things aren't perfect, they'll take a bit more abuse.
 
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