Bad pushrod

[78bigblock]

Open to any ideas. I had my #4 intake pushrod catastrophically fail. The upper ball end is completely gone. About 535 miles since rebuild. Comp cams magnum pushrod, comp cams 1.72:1 roller tip rocker. Set to zero lash then 1/2 turn. Looks like maybe it wasn't rotating properly and just chewed itself up. Replacements on order. Was this possibly due to setting it up too loose during break in? 1/4 turn... Or bad lifter? I'm at a loss. After cam break in I torqued everything down to 1/2. This is the only one I'm having issues with. I am however mulling the idea of yanking the motor and checking all of the bearings and cleaning out all of the metal particles. As minimal as it is.

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[SlickGTP]

I had that happen on one of mine after a rebuild and it turned out to be the rocker. It had a small defect in the socket and chewed up the pushrod. I bought a a new rocker and a then for the hell of it a whole new set of pushrods so that they would all be the same.

Here's what mine looked like:

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[78bigblock]

I changed the stud today and ordered a new pushrod and a new rocker arm.

 

[SlickGTP]

My guess is that you'll be good after putting the new parts in.

 

[GTME94]

One good thing is that the debris from the pushrod would go down the oil drain back and get filtered out. A main bearing would tend to send debris on to a rod bearing or somewhere else through an oil supply passage and cause more trouble.

 

[bobkyle2]

I'd yank that engine apart. Been there done that.

 

[Irishman999]

Im wondering if you have the wrong length push rods, if you mess with valve train stuff it can throw off valve train geometry. Easy way to check is to write all over the top of the valve with a marker, install the rocker and rotate the engine a few times. It leaves a line where the roller contacts the valve stem and it needs to be right in the center.

 

[78bigblock]

Irish I did that when I installed the lifters/pushrods/rocker arms. All of them were dead on center.

 

[Irishman999]

Irish I did that when I installed the lifters/pushrods/rocker arms. All of them were dead on center.

Hydraulic lifters?

 

[Irishman999]

Well I gotta get some sleep, so I figured I would leave with some ******** I typed up that might help even though I am in no way qualified to give advice.

Comps cams wont sell you a product that will eat a pushrod end like that, their level of quality is really good.

I think you have the valve train way tight, you said you adjusted everything during installing all this stuff and the engine is new. I went through the same thing with my big block, I actually got the engine in the truck and ready to fire before ordering push rods because I wanted to pressurize the lifters and get good measurements. That was just a preliminary adjustment, once I got it fired over and running I went back through and adjusted them with the engine warm and running.

If you ran your valve lash too loose there would be a very audible ticking noise the entire time. I think you ran them way too tight and might as well order all new push rods, then again its weird that it ran this long fine and only that one pushrod failed. Then again the more I learn about hydraulic lifters the more I get confused.

I am excited to see the conclusion.

 

[chengny]

Maybe excessive pre-load or a sticky metring disc on that lifter:

EVER WONDER WHY WHEN YOU PRELOAD THE LIFTER MORE THAN ABOUT A 1/4 TURN ON THE ROCKER ADJUSTMENT NUT THE VOLUME OF OIL SQUIRTING OUT OF THE PUSH RODS DROPS OFF RAPIDLY,

The seat in a hydraulic lifter rides on a cushion of pressurized oil, oil that's displaced up the push-rods as the cam lobe sweeps under the lifter base, as the lifter returns to the cam lobes base circle the lifters seat is pushed back up to full height by oil pressure (one reason lifters tend to click with low oil pressure)
the potential problem is that the total distance the seat supporting the pushrod moves is usually about .055 thousands, a full turn on a rocker nut is usually .040, so the more you preload the lifter the lower the volume of oil under the lifter seat

picture may help