Pantera #4033 - the Banzai Runner swallows the carb stud...

disapointing and fustrated are not even the feelings I have and its not even my engine

a frozen crank should indicate it did make it to a valve. do you think the size of the piece was small enoguh to make through which might be better than a bent valve. would pulling the valve covers tell you if it was?

condolences Garth

Best case scenario & my estimation..."1" bent valve...Mark

quote:

Originally posted by JFB #05177:
disapointing and fustrated are not even the feelings I have and its not even my engine

a frozen crank should indicate it did make it to a valve. do you think the size of the piece was small enoguh to make through which might be better than a bent valve. would pulling the valve covers tell you if it was?

Possibly if the "bent valve" BENT at it's fully open position, then there would be excessive valve lash between the tip of the valve stem & the rocker.

The engine not turning is a good indication of a bent valve.

The positive is that it happened whilst the engine was idling/low rpms minimizing the damage vs a 5,500 rpms engine seizure...Mark

Keep us posted - it's like a friend getting a sudden health problem - you have us all worried.

Good Luck -

Rocky

Wow Garth. Sorry to hear that man. Hope it's not too serious.

Wow that sucks...

Garth,

That sucks! I had a GT5-S in about to years ago that this happened to. The stud made it past the carb,past the valve and cracked the cylinder and beat the hell out of the piston.


Ron

Why would that break?

quote:

Why would that break?

My best guess so far...

As long as I've owned the car the top of the air cleaner showed witness marks of contact with the leading edge of the rear decklid. It's been like that for years. However, when I rebuilt my engine I swapped out the Edelbrock Performer intake for a Weiand Xcelerator 2V single plane intake manifold which I had the carb pad milled flat to minimize interference issues with the air cleaner and the rear decklid.

My best guess so far is that the air cleaner may sit a tiny bit higher with the changed intake and the decklid is making contact with it, applying a constant load rather than the occasional vibration scrape. I suspect a constant load or stress on the air cleaner stud combined with 3500+ miles of engine vibration may have work hardened the stud and caused a stress failure which occurred right atop the locknut I used to secure it to the carb to make sure it couldn't ever back out.

Tear down starts tonight. I'll share what I find.

Garth,

Unfortunately, I had a similar (not exact) experience a couple years ago.

To make a very long and sickening story very short, the set nut I had on the carb stud had loosened up and fallen into the carb. The resulting "marble on a roulette wheel" sound at a very minimal 10 miles an hour was something I had never heard before (and never want to hear again). I shut the engine off and had the car towed home.

The first cylinder it entered was #8 and it cocked the piston in the bore, cracking the cylinder in two places before exiting through the valve to see what other damage it could do.

Upon teardown, I found that the nut had visited every single cylinder as the nut came apart, getting smaller and smaller as each piston beat the snot out of it.

That 5 cent nut cost $5000 in new engine work and made a door stop out of the block.

I kid you not, I said to myself just 20 seconds before the incident took place, "Man, the Pantera is running really great today!"

I no longer that a set nut on the carb. I welded the wing nut to the stud where it exits the top of the air cleaner. If the stud ever loosens up, it just spins and can never fall in the carb.

I sincerely hope nothing even remotely like that happened to you.

quote:

Originally posted by garth66:
My best guess so far...
... a stress failure which occurred right atop the locknut...

I had recently commented on a failure in the same location (differnt device) as it is a common failure mode. the root of the thread is a stress concentrator and any side loading (bending) will fatigue there. if the air cleaner was touching the deck, then the engine vibrations were constanitly working the stud back and forth.
for the failure, I recomended to the customer to use a long coupling nut, ream out the top few threads so the untreaded section of the stud was inside the nut. however in this case, the best would be to eleminate the contact with the deck and the bending. making the stud not fail might force the failure into the carburator threaded section

quote:

I welded the wing nut to the stud where it exits the top of the air cleaner. If the stud ever loosens up, it just spins and can never fall in the carb.

Brilliant idea! This afternoon I was trying to think of how I could secure the air cleaner to the carb without risk of the stud (or a jamb nut) falling into the carb. Your solution is so much simpler (and better) than the things I was thinking of. I will definitely do that in the future!

Tonight's update...

Removed the carb and looked around the intake with a flashlight hoping to find that darn stud - no luck! Shoved an extendable magnet down each port hoping to pull the stud back out with it - no luck! Interestingly, no metal bits or shavings came back on the magnet either.

So off comes the intake so I can get a look down the intake ports in the heads...

Still no sign of the stud... I expected to see at least a bent valve or scratch marks in the aluminum head from the stud getting banged around atop a valve and or trying to go into a cylinder. But all the intake ports look undamaged.

Here are pictures of each cylinder's intake port...

#1

#2

#3

#4