Rough Start to New Year

maybe try a compression test , than you can maybe found out whitch valve or  cylinder  is the problem.

check the valve caps ,maybe hard to see when you have a hydraulic cam.

Simon

Thanks Simon,

I will try the compression test first.

I have a flat tappet ISKY cam if that makes a difference?  What am I looking for on the valve caps and is that checked down inside the intake? 

I can see inside the middle intake runners but can't see much in the outer 4 cylinders due to the longer intake runners and the curvature of the intake.

John

...'IT's' IN a Cylinder!! The Thud was The Piston Bending a Valve as the Stud Tried to pass Under, or Jamming a Piston. That is what Stopped the Engine...and You tried to restart. You're Going to have to Pull the Head(s). There will be Great Damage. In My View. Anything 'inside' the Air Filter, can come loose. Why Holley Leaves out 2 Screws in their Baseplates, and Why I Never place a Washer Under the Wingnut!! I Feel Your Pain!

Doing a 'Compression Check' means turning over the Engine. Enough Damage!

Happy New Year

MJ

when the sparkplugs are out of the heads , you also can turn loose the valve rockers till the springs are decompresed, use a pressure airgun into the sparkplug holes , when there is one leaking than there is the problem.

this way it is not needed for turning  the engine for protect further damage.

maybe you have luck and find the problem with a flexible magnet.

but most of the time there is a valve bented and one head needs pulled from the engine.

good luck,

Simon

There is no way you can do this without at least partially pulling the engine apart and you should not turn the engine over further unless by hand. You may be lucky and as it's 3" the stud is caught in an intake valve, but as Marlin said the seize was likely due to the piston hitting the valve, so at a minimum expect a bent valve or pushrod and potentially damaged piston and possibly bent rod. Only way to confirm is start pulling it apart. I'd pull the intake and rocker covers first to look in the runners and at the pushrods / rockers and see where it binds turning over by hand.

But honestly that is all just an autopsy attempt, if it were me I'd just pull the engine and strip it down.

I figured this would probably be the case but looking for a miracle.

I planned to do some work on the ZF this year so probably best to bite the bullet and pull everything.

Really sucks as this engine is a fresh rebuild with 4K miles on it.

Thanks for all the advice.

John

Stop turning the engine over and pull the intake...

If needed, pulling a cylinder head with the engine in the car is not difficult.   If you have cast iron heads, it is best use an engine crane.  It also gets easier after doing it a bunch of times.

I pulled the intake off and didn't see anything on the top side of the valves nor any scratching or scoring.

I decided to drain the oil and to my surprise at least 1 gallon of straight green anti-freeze came out, no milky oil at all.  I dumped the anti-freeze and went to drain it again then the oil, milky came out.

Last oil change was 1K miles ago.

At this point, I'm thinking a cracked block or somehow punched a hole in the aluminum heads?   These are Speed Master 3V heads for reference.

Engine is coming out but curious of the root cause of the failure.

Thanks,

John

That sucks, sorry to hear, I expect you to find a cracked cylinder wall.

Maybe do a leak down test and try to find the cylinder with the problem.  Then pull that cylinder head and inspect things.  If the problem is with the head, you might not need to pull the engine.  If the issue is in the block then no harm done.  You would be pulling the heads anyways when the engine out.

Good point Steve,

Now I'm curious to see what has happened.  I won't have the cherry picker back until the weekend so can't hurt to look.

Thanks,

John

If I get lucky and it's a head issue any thoughts on needing to replace all the bearings in the engine?  The engine ran 10-20 seconds at the most.

I have head gaskets go bad in my Cummins work trucks all the time and usually don't need to replace bearings if we catch it soon enough.

Thanks,
John

It's likely that the bearings will be fine but the cylinder will almost certainly need to be sleeved. I rebuilt the drivetrain in a GT5-S a few years ago for exactly this reason.

Ron

IMHO, allthread is evil and should NEVER be used for air cleaner studs!!!!   It isn't hardened at all........  Unless it was in the previous build, having it on the carb for only 4K miles should tell you how inadequate this material is to use in this application.....as a carb stud!

If this 3" piece is still in an intake port/valve you should be able to see it with one of those camera on a snake deals.....go in thru intake ports and or spark plug holes.....but with antifreeze in your oil.....your future task list seem obvious! Just a matter of which head comes off first......

BUMMER BIG TIME!  Hope it turns out to be salvageable!

Steve