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Kirkham Motorsports

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  #1 (permalink)  
Old 06-22-2019, 05:18 AM
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Default Messed up push rod and rocker in my 460

Hi, Yesterday I went to set the lash on my 460 that I have in a Cobra. It is a mechanical solid roller setup and has all comp cam valve train parts. The rockers are blue Ford AVO 1.73.

I was checking the lash and I got to one of the exhaust valves and found just over 0.200. It was so loose the rocker was basically floppy. I was able to see the end of the push rod and under side of the rocker was totally hammer'd. I pulled the intaked figuring it was a problem lifter or maybe cam issue. I pulled the lifter out to get a good look and both the lifter and cam look great. I see no problems with either of them. Best I can tell the valve and springs are fine also. There doesn't seem to be any hang up. The rocker stud was seated all the way also.

I think I caught this early as metal flake/bits are at the top of the cylinder near the problem area but I have no idea what caused it!

The rods are one piece. I don't know if it was maybe faulty? Or possibly the steel cup that the rod sits in on the rockers went bad?

Here are some pics..... Thanks in advance!


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Old 06-22-2019, 06:04 AM
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From your photo I wonder if that pushrod
tip was hardened properly.

Good news is you caught it early.

Have you drained/inspected oil/filter for metal
contamination yet? Just curious.

Best wishes to a speedy fix.
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Old 06-22-2019, 06:34 AM
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I have not yet drained the oil but it is on my list to do.

A friend who knows engines really well said that it just looks like a failed pushrod and that I need to make sure to get hardened pushrods.

The comp cam number on the push rod is 7934. I thought these were hardened?
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Old 06-22-2019, 07:30 AM
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It looks to me like the rocker had twisted side ways, the pushrod was out of the pocket, and the roller was no longer on the valve. It appears like it twisted both directions. If the beat up area on the edge of the roller tip and the beat up area beside the pocket line up with the pivot point, then I'm sure of it.

I didn't see any bend on the push-rod, at first glance, but pictures are 2 dimensional. Is this push-rod 0.200" shorter than the others? I would want to prove that the push-rod explains all of the slop.

Maybe the side pipes are too loud, maybe your hearing is not perfect, but that should have made a lot of noise for a long time. Not judging here. I just think this happened over a longer time period than you are thinking.

The worst thing is getting all the metal shavings cleaned up. If only someone would invent an aluminum magnet.
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Old 06-22-2019, 07:47 AM
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I did confirm that the 0.200 is the difference between the bad pushrod and a good one. When I started it up after the winter I remember thinking hmmmm...is that an exhaust leak? But it wasn't loud or clattery or bad sounding. It ran great with no issues. Then earlier this week when my wife and I were cruising together for the first time this year she mentioned "is it supposed to sound like that?" Which made me take pause and check the valve lash and I found the bad rocker and pushrod.
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Old 06-22-2019, 07:49 AM
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Also, no bend in the pushrod. I really have no explanation why the pushrod came out of the pocket other than it went bad. Or maybe the steel cup of the rocker pocked went bad.

Quote:
Originally Posted by olddog View Post
It looks to me like the rocker had twisted side ways, the pushrod was out of the pocket, and the roller was no longer on the valve. It appears like it twisted both directions. If the beat up area on the edge of the roller tip and the beat up area beside the pocket line up with the pivot point, then I'm sure of it.

I didn't see any bend on the push-rod, at first glance, but pictures are 2 dimensional. Is this push-rod 0.200" shorter than the others? I would want to prove that the push-rod explains all of the slop.

Maybe the side pipes are too loud, maybe your hearing is not perfect, but that should have made a lot of noise for a long time. Not judging here. I just think this happened over a longer time period than you are thinking.

The worst thing is getting all the metal shavings cleaned up. If only someone would invent an aluminum magnet.
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Old 06-22-2019, 09:11 AM
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Looking at the underside of the Rocker at the Valve it appears the Roller tip bearing failed. There are contact marks where it was hammering the spring retainer cap. The failure would allow the push rod to have enough play to start hammering the end of the push rod.
I'd "round file" the rocker set. The lifter, although may appear good the needle bearings are probably flat-spotted.

Last edited by spdbrake; 06-22-2019 at 09:32 AM.. Reason: additional info
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Old 06-22-2019, 02:45 PM
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Quote:
Originally Posted by jacobsed View Post
Also, no bend in the pushrod. I really have no explanation why the pushrod came out of the pocket other than it went bad. Or maybe the steel cup of the rocker pocked went bad.
I would say the push-rod had already shrank (beat down) to make the clearance for it to fall out of the pocket.

I, too, have wonder if the push-rod was incorrectly hardened. On the other hand, once the clearance is too much on a solid roller, it's like putting a demon in your engine with a sledge hammer. Something is going to get the **** beat out of it.


I also agree that the roller lifter has had the **** banged out of it. I wouldn't trust it. I'm not a fan of solid rollers. I hope the cam lobe is good. It's hard to see through a lifter whole. I would NOT spin it with my finger in it, but I would want to. Move it then feel it, in small movements, for two crank rotations. Man that would suck.

With the powdered metal, I would pull it, disassemble it, clean it. After I cleaned it, I would clean it again and again and again. Then make sure everything that goes back in is good. I would inspect the cam real carefully.

Last edited by olddog; 06-22-2019 at 02:49 PM..
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Old 06-23-2019, 04:28 AM
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The cam and lifter seem to be perfectly fine. I did buy a replacement lifter for good measure.

Quote:
Originally Posted by olddog View Post
I would say the push-rod had already shrank (beat down) to make the clearance for it to fall out of the pocket.

I, too, have wonder if the push-rod was incorrectly hardened. On the other hand, once the clearance is too much on a solid roller, it's like putting a demon in your engine with a sledge hammer. Something is going to get the **** beat out of it.


I also agree that the roller lifter has had the **** banged out of it. I wouldn't trust it. I'm not a fan of solid rollers. I hope the cam lobe is good. It's hard to see through a lifter whole. I would NOT spin it with my finger in it, but I would want to. Move it then feel it, in small movements, for two crank rotations. Man that would suck.

With the powdered metal, I would pull it, disassemble it, clean it. After I cleaned it, I would clean it again and again and again. Then make sure everything that goes back in is good. I would inspect the cam real carefully.
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Old 06-23-2019, 07:34 AM
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If you have an oil cooler or remote filter. I would pull the lines and see if there is any metal in them. There is a light you can shine that makes powdered metal show up. I cannot remember if it is a black light or what it was. If there is metal out in these, you know it's all through the engine. Especially if there is metal in the line coming out of the filter. You can clean lines, but an oil cooler is hard to prove you got it clean.

If your not going to pull it apart to clean it, I would at least do this. Clean everything up top under both valve covers. Sounds like the intake is already off so clean everything there too. Then drain the oil. Then pour kerosene over all the surfaces up top and let it run out the drain. It would be interesting to let the Kerosene drain through a clean white cloth to inspect for powdered metal. A gallon or two should do the trick. Let it drip dry. Then pour a couple quarts of oil and let it flush all the kerosene out the drain.

Replace filter and put cheap oil in it. Idle it a 5 minutes, then replace filter and oil again.
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Old 06-23-2019, 10:16 AM
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The cause of your failure is in the first picture. The pushrod cup in the rocker arm broke. The pushrod ate itself up grinding against the sharp edge of the broken cup while the rocker flopped left and right dinging the roller tip end against the spring retainer on both sides of the tip.

Replace the rocker, pushrod and use that new roller lifter you just bought to replace the old one, just to be safe.


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Old 06-24-2019, 02:57 AM
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Quote:
Originally Posted by eschaider View Post
The cause of your failure is in the first picture. The pushrod cup in the rocker arm broke. The pushrod ate itself up grinding against the sharp edge of the broken cup while the rocker flopped left and right dinging the roller tip end against the spring retainer on both sides of the tip.

Replace the rocker, pushrod and use that new roller lifter you just bought to replace the old one, just to be safe.


Ed
I would say the pushrod cup seat has been starving for oil.
Many of this type of rocker system does not have continuous oil flow.
The cup and pushrod tip have pounded themselves away, the rocker has increased it's rocker ratio, and possibly driven the valve to coil bind, allowing for the increased valve clearance.

I would be looking at replacing any/all of the pushrods and rockers.
I would also run the engine with the valve covers off checking for oil flow after reassembly. And do as olddog above has mentioned about flushing the engine.

Gary
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Old 06-24-2019, 12:10 PM
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Quote:
Originally Posted by Gaz64 View Post
I would say the pushrod cup seat has been starving for oil.
Many of this type of rocker system does not have continuous oil flow.
The cup and pushrod tip have pounded themselves away, the rocker has increased it's rocker ratio, and possibly driven the valve to coil bind, allowing for the increased valve clearance.

I would be looking at replacing any/all of the pushrods and rockers.
I would also run the engine with the valve covers off checking for oil flow after reassembly. And do as olddog above has mentioned about flushing the engine.

Gary
I was thinking the same thing initially, Gary. What changed my mind was the lack of heat discoloration that usually accompanies an oil starvation failure. My suspicion is, if the pushrod cup had a scratch or perhaps a hairline crack that was the weak link and it finally gave up the ghost with all the attendant carnage.

The more probable (big) contributing factor, was very likely poor rocker geometry attributable to too short of a pushrod for the pieces being used that never was investigated, measured or corrected. The short pushrod as already noted would put the full load of opening the valve on the side of the pushrod cup instead of in the center. The abuse does not take a long time before it extracts its pound of flesh.

When the pushrod is short the rocker fulcrum has to be lower to make contact with the pushrod. As you lower the rocker fulcrum the existing pushrod increasingly pushes on the side of the cup. Cups are pretty hard little devils. Push on the side instead of the approximate center long enough and you can induce this type of failure.

Determining the correct pushrod length to obtain the correct rocker geometry is always the responsibility of the engine builder and something that needs to be done anytime you build an engine from parts. I suspect that step was overlooked or just not known to this builder. In fairness all the other rockers could be at the same risk of a similar type of failure and there is no way to know w/o checking the geometry.

Here is a teaser with respect to the geometry issues off the T&D website, T&D's focus in their explanation is prevention of premature guide wear;

The main thing we are looking for in geometry is the pattern on the valve stem to ensure that valve guide wear is at a minimum.

The roller tip needs to start towards the intake port side of the head when the valve is closed. The rocker should then roll out to just past center towards the exhaust side of the head at half lift. Then from half lift to full lift, it should roll back to where it originated on the intake port side of the valve stem. The amount of tip travel will be directly affected by how much lift there is at the valve.

Example: If you have 0.550 lift, the roller tip should start 0.020-0.025 before centerline of the valve stem. If you had 0.650 lift, this pattern will roll back towards the intake side of the head and be 0.025-0.030.


The OP's engine looks like it may have had very short pushrods. With stud mounted rockers an uniformed engine builder would just snug down the adjuster until the pushrod made contact with the rocker. This is high stakes poker no matter how you cut the cake.

There are several good videos on YouTube. I did a quick search and found this one, from Prestige Motorsports, click here Rocker Geometry (you need to wait for the YouTube commercial to finish). The video is fairly well organized and presented. By far the best explanations I have seen come from T&D in their tech literature that accompanies their products. I did not check but I would not be surprised to discover that you can download their installation doc.


Ed
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Old 06-24-2019, 09:18 PM
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Yes Ed, I think you are right on the money.

Rocker geometry is the cause, and so far one has failed, no doubt some of the other 15 will show signs of this.

The OP should remove all rockers and pushrods for further examination.

I spend more time on rocker geometry to get the rocker "strike" correct, and all the clearances necessary, than the short motor assembly on some of my builds.

I agree, and have no doubt that the engine builder of this engine in question has not addressed the valve train correctly.

Gary
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Old 06-24-2019, 09:35 PM
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Got it all put back together and running tonight. Gotta say she runs strong and sounds great. Much better than before. I did check the other rockers and push rods and they look perfect. I also inspected the geometry based on the youtube video and to my eye I don't see any problems. The rockers are sitting nice and centered on the valve stem like in the video. Not too far forward or too far back. The pushrods are angled directly into the cups. I don't see any angle that would indicate its pushing out of the cup. I filtered the oil and found nothing in it. I'll cut apart the oil filter later when I have time. I cleaned up a bunch of bits that were under the bad rocker at the bottom of the head so hopefully that was most of it and anything else is in the filter.
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Old 06-24-2019, 10:14 PM
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Here is another video I like about rocker geometry:

https://www.youtube.com/watch?v=o5is9BsH5OU

Gary
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Old 06-24-2019, 11:21 PM
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Quote:
Originally Posted by Gaz64 View Post
Here is another video I like about rocker geometry:

https://www.youtube.com/watch?v=o5is9BsH5OU

Gary
Good pick Gary and an excellent presentation with a clear explanation of the issue and how to resolve it in a low tech easy to do fashion. This kind of engine build detail is the stuff that novice builders often inadvertently overlook and it does make a difference it also changes cam to cam ...

Ed
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Old 06-24-2019, 11:54 PM
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Good pick Gary and an excellent presentation with a clear explanation of the issue and how to resolve it in a low tech easy to do fashion. This kind of engine build detail is the stuff that novice builders often inadvertently overlook and it does make a difference it also changes cam to cam ...

Ed
Yes, that's correct. Any change - camshaft, heads, valve stem length, needs geometry checked.

Gary
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