wrecked engine -- here's the damage
 

lucky lucky me ... a broken pushrod and a bent pushrod

as said it sounded like when you remove a spark plug from running engine.
the exhaust pushrod for #5 cylinder broke. since the exhaust valve couldn't open anymore the gasses went out back through the carb.

the insurance company towed the car back to buddies place. removed the rocker cover and you could see it immediately since one rocker was sideways.
well i pulled the pushrod out.
to check for length I pulled the intake pushrod as well, and that one was bent.
I'm actually convinced it has always been bent. since i got the engine the first thing I did was to correct a tapping on the intake of #5. adjusted the rocker so it would stop. this was probably caused byh the pushrod being bent.

I haved replaced the two with the one from my 289. they are 2mm shorter (0.08"). engine runs great again.
i'll get a full set of correct length pushrods now. but unfortunately found somethign else.
the lobe of the #5 intake on cam is nearly gone. when running the engine with rocker covers off I saw the rockers moving, you can make out a lift at valve. not measured. but the #5 intake travels a lot less than all the others on that bank. so I'll need a new cam soon

here's the pic, i post the video once uploaded

http://lh6.ggpht.com/_7rDLe507VfE/S5...2/pushrods.jpg

and here#s the video. obviously the valvetrain is too quick for the camera to pick it up

http://www.youtube.com/watch?v=E0DMhMnwteM

Glad that was an easy fix for you. I know ours scared the s*it out of us when it started knocking, but thankfully was only a broken rocker stud.

OK, my question is, why did a hardened pushrod break? What is the underlying cause?

If you are running hydralic lifters then i would recommend replacing them. A very good possibility is that your lifter is sticking in the extended position and as the valve train heats up and expands the lifter isnt retacting as it should. This will cause the pushrod to bend and the lobe to start wearing. The pushrods are designed to be the weak point in the valve train for just this reason so they bend and save the rest of the valve train.

I am with 2+2, what is the cause of the problem?

The answer might have been piston contact with the valves VIA a combination of the following--

1. engine built with valves that get very close to piston to start with.

2. High engine speed causing valve float

3. hydraulic lifters pumping up


But this does not seem likely if the cam seems to be worn on that specific cylinder.

A mystery. I think I would baby the car around for a while to see what develops.

Where's the missing piece? If you suspect a wiped out lobe, I'd cut the filter open and see if there are metal shavings. Do you think you bought the engine with a wiped lobe? Has there been a miss since you purchased the engine? I would definitely see if there are metal shaving in the filter and taking a retractable magnet and sweeping the bottom of the pan through the plug hole. You can also use a dial indicator on the rocker to see if the lobe is wiped. I suspect too that you over revved the engine. Good luck and keep us posted.

thanks for all the comment:
2+2: very good question and one that I should always consider when something breaks.
as in the picture it broke at the pressed (or screwed?) in ball. probably the weakest link in them.

jdraper: glad they bend and break, otherwise something else (more trouble) goes.
as for the wiped lobe. i think i can't hear if one engine with 8 cylinders has a lower intake lift. it's not misfiring and still isn't. the lobe is not completely gone, but if the lift at valve is .5" i'd say the intake is about half of it. I'll definetly buy a dial to measure lift at cam on the lobes ...

JMD, to your mystery. i need to clarify:
the exhaust is the one i smashed, the intake (bent) i believe was always bent since I have the engine. that would explain why i had to reset the rocker.

I believe what actually caused it was me hungover, not waiting for the engine to properly warm and making an ass flooring it in first and enjoying that wheelspin (for a bit too long)

valley:
the missing piece I haven't found. it wasn't on the head. I warmed the engine, changed oil. havent found it either. but I will go back and cut the filter. good idea. i haven't seen any shrapnel and bad things in the old oil tough


anyways, the plans are:
get 2 correct length pushrods (don't like having them 2mm shorter)

then buy a kit: cam, lifter and a pushrod length checker, then buy the correct length rods. until then baby it

does that sound like a reasonable plan?

Yes, something definitely caused the pushrod to break, and you need to find out what it was.

I'd swap in a roller cam.

I'm glad you engine damage is not nearly as bad as it could have been.

Couldn't it have bent just from being over reved?