7.3 Carnage.

***cleatus12r*** · #1 Wed, February 3rd, 2021, 09:43 PM

I rebuilt a 7.3L for a guy about a year and a half ago. It turns out that the engine had been rebuilt ALREADY just before this guy bought it.

I'll post two pictures here and let someone take a crack at what caused the failure. This was a 1000% non-fixable block as you'll see. What was the root cause of the failure?

Good luck. Winner gets.....well......to say he guessed the cause.

***Power Hungry*** · #2 Thu, February 4th, 2021, 01:47 AM

Aren't the valves supposed to be in the Cylinder Head, not the top of the piston?

My initial guess would be bad seat pressure on the springs which caused valve float. Or possible, trying to run an exhaust brake which again caused valve float.

As you indicated, that block is scrap at this point!

***cleatus12r*** · #3 Thu, February 4th, 2021, 08:31 AM

Yes, the valves in that particular cylinder are supposed to be in the head, not the piston.

However, they did not travel from their home due to any issue listed.

A couple more pictures:
Cylinder 6 was the initial failure and as you can see, the block is cracked at the 2 o'clock position in #6 (picture rotated 90 degrees counterclockwise) and cylinder #8 that ate some of the chunks (#6 wasn't selfish and decided to share), cracked the cylinder wall at the 2 o'clock position as well. That whole section of the block was BROKEN all the way to the lifter bores. The tuning that was flashed to the PCM long before I ever saw this thing...well...it was HOT. But that's not why it failed.

The answer will be revealed a bit later but here's another hint: There is a reason the cylinder heads were pictured side by side and keep in mind that this engine was recently remanufactured.

***Longshot270*** · #4 Thu, February 4th, 2021, 04:10 PM

Did they spin it too fast for too long?

***Power Hungry*** · #5 Thu, February 4th, 2021, 08:55 PM

Oh, it looks like the intake and exhaust valves are swapped on the one head.

***cleatus12r*** · #6 Thu, February 4th, 2021, 09:05 PM

BINGO!

They are the same diameter and length. The seats are cut at different angles but they'll still seal. The problem? The margin becomes too narrow and the valve material is WAY different. The exhaust valve is an inconel alloy and the intake is something ferrous that is way less heat resistant.

You win, Bill!

***Power Hungry*** · #7 Thu, February 4th, 2021, 10:24 PM

Quote:

Originally Posted by cleatus12r

BINGO!

They are the same diameter and length. The seats are cut at different angles but they'll still seal. The problem? The margin becomes too narrow and the valve material is WAY different. The exhaust valve is an inconel alloy and the intake is something ferrous that is way less heat resistant.

You win, Bill!

Thanks. I was trying to look at the pics on my phone earlier. Couldn't make out much detail. Now that I'm on the computer, it's much more evident.

Now with that said, maybe they confused the head with a prototype reverse-flow setup. LOL

***cleatus12r*** · #8 Thu, February 4th, 2021, 10:45 PM

At least one head was assembled correctly and able to be salvaged.

I bet it made one heck of a racket when it let go. The guy was pulling a trailer up a pretty good hill when it quit running.

jimcricket · #9 Tue, November 28th, 2023, 01:07 PM

Quote:

Originally Posted by cleatus12r

At least one head was assembled correctly and able to be salvaged.

I bet it made one heck of a racket when it let go. The guy was pulling a trailer up a pretty good hill when it quit running.

curious, were you able to get the mfg/rebuild shop to cover the cost due to incorrect build?