I was just talking to Dwayne Porter about rockers arms the other day and he mentioned that he had more than one instant where the lifter bled down on a lobe of the cam at full lift at shutdown. Then at startup, the collapsed lifter let the pushrod fall out of the rocker arm. Our discussion was around certain brands of ball/ball rockers and higher lift hydraulic cams. So, not doubting his word, I’ve been looking at the ball/cup design rockers that have a deeper pushrod cup that may prevent that. Well, on another build, I’m helping a bud with a stock type rebuild. This motor was not machined by a higher performance shop and it was not assembled by a pro that checks everything, so there are a few unknowns here. My bud made several mistakes with this motor. I won’t go through all of them but to get to the point, he let it idle excessively in his drive. Last weekend, he backed it out of the garage and let it warm up as usual and shut it off for a couple of hours. Everything was fine at shutdown with excellent oil pressure. He then started it back up only to have lots of metallic noise and zero oil pressure. Pulling the valve cover and intake revealed a pushrod had fallen out of the rocker and even fell halfway down the around the camshaft. In addition, it was bent on at the top and you could see the mark on the rocker where it had fallen toward the rocker shaft. The next time the lobe came up, it wadded up the pushrod and spit the lifter. This was a MP Performance .484 lift with 241 degrees duration @ 50 and STOCK stamped rockers. Upon further inspection, we found two other lobes flattened on the cam. One message here is DONT LEFT YOUR FLAT TAPPET CAM ENGINES IDLE IN THE DRIVEWAY. The other is a question. This is a new personal experience for me, but has anyone else experienced this. Dwayne and I did not discuss stock stuff, but I’m just wondering if we got a really poor set of lifter that bled rather quickly? Dwayne, now I need two cams! Lol!

I’ve never heard of the exact problem we had with the rockers that have cup style adjusters and the pushrods falling out, happen with stock stamped rockers.

But that doesn’t mean it “couldn’t” happen.
However.....the only way I could see it happening with stock rockers is if there was basically zero preload on the lifter.

The aftermarket rocker with the cup adjuster has the cup depth about .060” shallower than a stock stamped rocker.

The stamped rocker cup is basically as deep as there is total lifter plunger travel....... so it would be pretty unlikely the pushrod would fall out with things set up “normally”.
However...... if the cam is going away and the bottom of the lifter is worn away....... and you have minimal preload...... it could happen.

With the aftermarket rockers that use cup style adjusters, you’d want to make sure the lifter plunger was closer to being bottomed out than what the depth of the adjuster cup is........ with a little safety margin added in.

This would usually have the lifter preload set outside the range of where the lifter manufacturers recommend.

Edit- I just measured a couple pieces to make sure I was remembering things correctly.
The plunger travel on a std hyd lifter is .200”.
The pushrod cup depth on a stock rocker is .180”.
So, with preload over .020”, theoretically the pushrod couldn’t fall out.

The cup in the aftermarket adjuster screw is only 120” deep....... so in theory you’d need to be running .080”+ preload to insure the pushrod couldn’t fall out.

It requires a specific set of circumstances to be in place for the pushrod falling out to occur.
-Lifter is on the closing side of the cam
-lobe lift is slightly more than the adjuster cup depth + preload
-preload is less than plunger travel minus adjuster cup depth
-lifter will not stay pumped up against spring load after shut down

So, the lifter bleeds off after shut down from the spring load of the valve being open.
The valve closes until it rests on the seat.
Now there is no longer any real tension holding the pushrod in place.
As the starter is engaged, the rotation of the cam causes the lifter to go lower in its bore(because it was on the closing side of the cam), and since the valve is already closed the rocker arm isn’t following that downward motion of the lifter/pushrod...... a gap is created....... and the pushrod falls out of the adjuster screw.

We had a heck of a time figuring out what was going on with a motor that experienced this very situation multiple times.
That motor had the rockers with the .120” deep adjuster screws and set up at about .020” preload.

Me thinks the pushrod fell out off of one of the flat lobe lifters, correct

That’s the first thing I thought. It was from a good lobe.

I’ll get the motor in a week or so and maybe I can figure it out and fix it.

this was on a hydraulic lifter FT with the stock, stamped rockers, correct ?

Could it be not enough retainer to guide/seal clearance causing bind and trashing cam and valvetrain.

Yes, it’s hydralic flat tappet and stock stamped steel. Don’t know anything about the heads other than he bought reconditioned 452 heads from Indy cly heads.