I'm not sure why it broke.  I replaced them, made sure the valves were opening and closing as they should.  It's running good.  Performance is the same so I guess nothing else is wrong.  I think the bent one is the result of firing the engine with the exhaust valve closed.

Should I replace this rocker arm? 

      recently there was a thread concerning the same thing. I also have been experiancing the same problem. New motor, about 1200 miles on it, all new push rods from NAPA, and rebuilt rocker assemblys. Sure can't figure that out. I'm going to start adding Marvel Mystery Oil in the fuel and see if that makes any difference. I also though of going to the larger diameter rods through Murmmunt  but don't know if there will be any problem with the "G" rockers that have using the bigger ones. I have a very boring stock cam too, nothing loopy.

                                        Michael

I talked at length with Mummert on rocker/pushrod geometry and he feels that it is very important, but difficult to change on a Y-Block outside of pushrod length.  It is my personal opinion that valve spring height will change the geometry and along with the higher lift cams, it is very possible that the base circle is a smaller diameter and therefor might start the rocker/pushrod angle at a stressful position with too short a rod.  Therefor short of shimming the rocker towers, like Mummert says, pushrod length is the key.  We check the geometry very carefully and make sure we order the correct length of pushrod.

Defective pushrod?  Stressful geometry angle?  At least it is something to think about.

Sorry about the drawings............they won't get any better!  Also note that too short a rod will require more adjuster showing below the rocker.  Adjustable rods to calculate the correct length are available from CompCams and I have seen some very effective home made units.

I feel brave with these comments, remember, Tim has the final word on our builds.  I guess he is just letting me ramble here.

Your pushrod has a radial break under the cup (a sign of excessive compression).  Your valve came to a sudden stop, but the lifter kept pushing on the rod.  Somehow, either the valve got stuck and couldn't go down any further (not likely), or your valve ran out of stroke from something else like a collapsed spring, or from too much shim, or the lash adjust was too tight.  The pushrod collapsed at the weakest point, and came to a violent end from excessive pressure.

Dave.

PS: I did get to be the first Columbus dude to ride in Charlie's truck. Sounds hard!

Shaft rockers are not to be confused with those rockers that are supported by a rocker arm stud and the height of which are fixed by the length of the pushrod.  Shaft rockers are at a fixed location or pivot point which makes geometry at the valve dependent upon the rocker stand height and not the length of the pushrod.  The length of the pushrod on a shaft rocker arm setup simply alters the rocker arm ratio.  That’s the simple explanation.  More detail on these subjects can be found at the following links.

Rocker arm geometry for shaft mounted rockers

Altering the rocker ratio by changing the pushrod length

Charley.  Your rocker arm is reusable as long as the adjuster screw still works freely.

I’m voting on defective cups on the pushrods and suspect that the problem will not end until all the pushrods have been replaced.  I observed a similar problem two weeks ago when breaking in a Y engine that was also Dove rocker equipped prior to performing a dyno session on that engine.  The pushrods I had trouble with are similar in manufacturing appearance to yours for what it's worth.

At ten minutes into the camshaft breakin period on the engine in question, one of the pushrods had chipped out the side of its cup.  It was subsequently replaced and camshaft breakin then completed.  At that point, two more pushrods also had chipped ends.  A hard look at the remainder of the pushrods showed four more with visible cracks in the cups.  At this point, all the pushrods were replaced with a stock tubular set of the same length (8.00”) and the problem was resolved.  Eleven dyno pulls and three intake manifolds later, the stock pushrods are still holding up just fine.  The final analysis on the broken pushrods was that the cups were slightly undersized allowing the rocker adjusters to not seat far enough down in the cup and that was simply putting too much pressure on the upper portion of the cup.  The Dove roller rockers in this case received a clean bill of health and were absolved of being the problem.

Here’s pics of the faulty pushrods, both the ones with chipped cups and those found with cracks.

And here’s a pic of the stock pushrod style that replaced the set in question and also a picture of some Smith Brothers pushrods going into another Y.

It's easy to check each spring by inching the crank and checking for more valve travel when each valve is fully open (down).  Rocker ratios, fulcrum points, and valve stem heights are secondary to valve stem stroke limits.  Some guys machine the tops of their guides to accommodate more travel (provided the spring has more travel left).  It's easy to see, when we marry different brands of parts, they may not be compatible when stacked.  Hope this helps, and I hope you check your other spring Shut-heights.

Dave

 By the way Ted, thank you for the pics of the Flathead pump. I sent you an email but it came back to me, I seem to have that problem everytime i send you something might want to look into that.

You and I are alike.  We look for the professional written word before we speak.  I too was armed with the CompCams info on rocker geometry before I talked to JM.  Ted made the long story short by explaining the CompCams info was based on stud mounted rockers.

By the way Ted and Tim, thanks for agreeing with me on Charley's problem.

mctim64 (5/21/2009)

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By the way Ted, thank you for the pics of the Flathead pump. I sent you an email but it came back to me, I seem to have that problem everytime i send you something might want to look into that.

Tim.  Thanks for the heads up about the email.  Have been struggling with recent ISP problems and have noticed that the incoming email count has also been down so I’m apparently not getting everything that’s being sent my way.  And I can’t say for sure if everything I send out is indeed going out either as I don’t get any error messages on my end.  But relieved to hear you received the pics I sent you.

The customer supplied the pushrods but they initially came from J.M.  Didn’t see any thing that looked like part numbers on them though.

Charlie,

thanks for posting the part #s I have just completed three engines and one I installed push rods that looked something like yours, I still have the engine in my garage so I checked and they have a different cup on them and don't seem to even contact the upper edge. I get my HP pushrods through Clevite the ones that are similar to yours are part # 215-4041 and the heavier ones are 215-4150. I know a lot of parts companies don't make there own parts and farm them out so the quality is not always consistent but I have had good luck so far with Clevite.

The push rod on the top is the 215-4150 it is 3/8" in dia. and probably a little over kill but they do hold up. If Bing reads this these are what is in your engine. The bottom picture shows the wear pattern, a little hard to see but it covers the whole area of the cup.

Hope this is a help.

Hindsight is 20/20, but I wonder why so many different pushrod cup sizes sold for the Y?  Does it mean every aftermarket setup needs to be clearance-checked?  Then, do they need to be ground or lapped to make the ball seat at the bottom to match OEM?

I'm learning new stuff every day on this site.  Thanks.

(As a side note, heavier valve train parts cause valves to float.  That's why lighter-hollow pushrods, etc.  Ex: Overhead cams elliminated pushrods, lifters, and a ton of kinetic energy. 
That allowed lighter springs to aid in the abreviated kinetic energy.)

      Was the diameter of the Dove balls correct, and round? Obviously not the problem but a contributor?

Charlie, hope you find the problem with the breaking pushrods, just make sure they are sized correctly and that there is enough adjustment on the ball so that the cup doesn't come into contact with the rocker as it opens fully.

 Bingo!!! Especially since the end of the pushrod looks to have a larger od cup than the tubular version. At least from the photos. The cup wear sure looks like a too small recess though in all the photos.

I am having a great Sunday afternoon doing what I like best, building engines, and I am in the middle of a 292 for a guy in Texas that has asked me twice to build Ys for him. What I have is a set of push rods that were purchased from John Mummert and as you can see they have a perfect fit ball to cup. I sprayed the cup with graphite and rubbed the rocker ball around in it to mark it and the pattern was just right. I just want to post these pictures to show that if there were some bad push rods out there I'm sure John dose not sell them knowingly.

You're a good Machinist/Die Maker, Tim.  Could you shoot a light coat of layout fluid in that cup, and show some mating witness marks?  As long as the ball seats at the bottom, it may have up to a .010" clearance fit.

 -  Dave Dare

I think the picture a few posts back shows the proper contact area better, it's hard to get a perfect picture with detail, it is touching a good 2/3 of the cup but not the upper edge.

                                                    Michael

         Didn't know that, always thought it was just effective length. guess I never bought any Clevite pushrods.

One of your statements caught my eye.  The mopar pushrod.  I wonder if the ball cup on a mopar pushrod is the wrong size, and whoever decided their mopar rods would fit Y blocks were only looking at length.  If the cup was too small, the ball would keep trying to wedge itself into the cup and possible finally fracture it.  I measured a used Y ball a couple days ago, it's .360" diameter.

                                 Michael

(quote) If Mellings (& others) use effective length & Clevite uses overall length, now we're are trying to compare apples & oranges....Ford and others use overall length, seems melling is one of the few that use effective length, just goes to show when you order one has to ask many questions.

The picures above: left to right are new Elgin pushrod, original 57 Merc 312 pushrod, next original 56 Ford 272 pushrod (note larger cup head OD on the 57 vs 56 beside it) and furthest right NOS E&F code pushrod.

I had a little time today to do some measurements on pushrods, these measurements maybe not 100% accurate as I used a vernier caliper.

New Elgin pushrod overall 8.131", socket depth 0.150", effective length 7.981" 

Original 57 merc  pushrod 8.139", socket depth 0.145", effective length 7.991"

Original 56 272 pushrod 8.10", socket depth 0.113", effective length 7.986"

NOS Ford E&F code pushrod  8.068", socket depth 0.187", effective length 7.881" 

You can see all the pushrods except the E&F code pushrod are within +/- ).005"  of each other

The Melling effective length of 7.967 would be slightly shorter by 20 thou +/- 5 thou

The E&F cade pushrod is about 30 thou shorter overall however is  about 100 thou shorter on effective length as it has a very deep socket of 0.187"    

One thing I thought about is does the Dove rocker has a recess above the socket ball to allow clearance for the pushrod to have free movement when the valve is in max open position. If it does not have this clearance when valve is fully open the cup could become very leveraged  and break as the pictures show. I don't have Dove rocker to compare and the pictures do not show the adjuster stud and ball clearly.

marv