*update* ever see a pushrod do this?
Safety Car
Joined: Jan 2001
Posts: 3,637
Likes: 27
From: Norwalk Ct
I had this happen to me.
I had the guides replaced in my heads and installed stainless valves. Apparantly the guides where very "tight" so when the engine got to a certain temp the guide grabbed the valve, the rocker arm goes loose, the tip of the pushrod falls out of the rocker hole and increases valve lift enuff for the valve to hit the piston, and the pushrod was the weakest link and resulted in something like you show in your picture. Had the guides clearenced enuff...and no more issues.
Nick
I had the guides replaced in my heads and installed stainless valves. Apparantly the guides where very "tight" so when the engine got to a certain temp the guide grabbed the valve, the rocker arm goes loose, the tip of the pushrod falls out of the rocker hole and increases valve lift enuff for the valve to hit the piston, and the pushrod was the weakest link and resulted in something like you show in your picture. Had the guides clearenced enuff...and no more issues.
Nick
Melting Slicks
Joined: Feb 2004
Posts: 2,435
Likes: 0
From: largo florida
Originally Posted by Ex_F-Body_Enthusiast
To get the extra clearance for polylocks and/or roller rockers, you can try doubling up the valvecover gaskets by glueing them together with 3M Trim Adhesive or get the Felpro fatties. . .
Melting Slicks
Joined: Nov 2003
Posts: 2,362
Likes: 1
From: San Antonio TX
No you do not need Poly Locks. You can purchase the locking nuts along with the groved pivot ***** and long slot rockers from GM for a decent price. And you still may need to just barely clearance the rocker arm slot where the stud is for enough clearance if they hit. They may not hit at low rpm but up in the high rpm they may so just something more to check. But when you put it all back together and go to set the valves set them a little loose with the engine cold then start the engine and readjust the rockers while the engine is running. Follow the MF specs as far as when they stop clicking turn in one quarter turn or half. If you want more info on this just pm me and I would be glad to explain it in more detail. 
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by vader86
Somethings not right in the valvetrain elsewhere too then, only time I've seen that is when the piston smacks the valve. If the valve springs are new and you havent floated them, this shouldnt happen.
This shouldn't happen unless something went solid. For something to go solid the piston hit the valve or the quide to retainer clearance is not enough. Just a nut backing off doesn't make sense. It would have become very noisy.Lack of retainer to guide clearnace usually shows up as a destroyed valve seal and in some cases mushroomed ends of the valve.
I would bet on piston hitting the valve.
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Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
I had a rocker nut backing off on the solid lifter L71 heads . The pushrod shot up and holed the valve cover being stuck in it.
The rod was still perfectly straight , actually, I reused it for a while without further problems.
The Lock nuts all got replaced after this.
Luckily it was a intake valve, so it didn't harm the engine staying stuck closed.
I also hada exhaust valve staying closed once due to e broken rocker arm and that does make a hell of noise as the exploded gas can not escape. I was still able to drive the car off the highway for a over a mile and thought the engine would explode, so noisy it was.
But your problem seems to be an other one, as the rocker arm was still in position.
Rgds. Gunther
I had a rocker nut backing off on the solid lifter L71 heads . The pushrod shot up and holed the valve cover being stuck in it.
The rod was still perfectly straight , actually, I reused it for a while without further problems.
The Lock nuts all got replaced after this.
Luckily it was a intake valve, so it didn't harm the engine staying stuck closed.
I also hada exhaust valve staying closed once due to e broken rocker arm and that does make a hell of noise as the exploded gas can not escape. I was still able to drive the car off the highway for a over a mile and thought the engine would explode, so noisy it was.
But your problem seems to be an other one, as the rocker arm was still in position.
Rgds. Gunther