[Jim Moshier]

I agree ....take a breather, Walk away....come back in a couple days with a clear head! if the plugs were smashed, something is a miss or separated. Hope its something small!

Jim

[Joe's Garage]

Since you mentioned changing back to the heavy valve springs from the lighter 'checker' springs, there's a pretty good possibility that the keepers on one of the springs for cylinder #1 did NOT seat correctly.

That would explain the cascade that would cause the engine to stop turning. (I hate using the word 'seized').

And to add my voice to the chorus, if you get frustrated WALK AWAY for a day or two

[wbnapier]

Update-

Tranny removed. No issue with the tranny. The input shaft spins free. Looking in the bell housing hole, no apparent issues.

With the tranny out, starter out, dizzy out, fuel pump out, pullys loose, and rockers loose, I put a breaker bar on the crank and it is still seized in both directions.

To confirm, all valves ends and springs appear good and held up by the keepers. I didn't do the straight edge deal, but I think that would be a good idea.

I put a borescope in the timing cover, all looks good. Pics attached. It's very difficult to get good pics of the some cylinders where the piston sits high in the hole. Some pistons are clean others are dirty.

The lift plate is on the intake and I can pull the engine tomorrow night and put it on the stand. Saturday, I would pull the heads and pan and reassess. I have Monday off, and if I want to get deep, I can drive the engine to the machinist who is about an hour away.

[694.1]

Plus- We want to know what happened! Maybe something in the timing set let loose?

[abefromen]

Remove the fuel pump and look inside with the borescope.

[sdbob]

I've been there. Like others have said take a break. Then set a goal for your family duties, then the car. No one was hurt. You wanted this GTO ,so relax it will be figured out.Take your time. It's easy to get discouraged. I've done it more than once. I had to re machine 2nd time a SD455,luckily the machinist to screw up the heads to bad.Do not quit! Good luck.

[tom s]

Get the trans out and starter out and then try to turn it over with a breaker bar.Tom

[lust4speed]

Only wild card that blows out a lot of guesses is the closed up sparkplug gap. We can come up with some cool scenarios, but the closed gap still says something was floating around those three cylinders and not a bottom end seizure -- but mild since the borescope didn't find any massive trashing.

Did you try and turn the engine once the starter was dropped and the starter pinion was off the flywheel? There's a possibility that the starter dying after engaging the ring gear could keep the engine locked up. Even if you get lucky and the engine turns over after removing the starter you still need to trace down what closed up the gaps.

[johnta1]

Only wild card that blows out a lot of guesses is the closed up sparkplug gap. We can come up with some cool scenarios, but the closed gap still says something was floating around those three cylinders and not a bottom end seizure -- but mild since the borescope didn't find any massive trashing.

Most closed gaps on plugs I've seen (more than one plug) is from rod bearings spun that let the piston hit the plugs. But is usually accompanied by noise. The no noise thing is what is strange.

Weren't 4 wheeling were you? I've seen a chuck of wood get stuck between the damper and the oil pan. Locked it up quick. But also noticeable.

[wbnapier]

Yes, the first thing I did Monday am was pull the starter to make sure there was no pinion issue interfering with the flywheel. Next will be tranny.

[chuckies76ta]

Timing chain..Came loose.

[tom s]

Mick,thats why I suggested to pull the trans and starter!Tom

[hgiv]

I'm going way in here.. and a bit over a guys head.. but... I think the plugs are the most telling. Can't get around that despite all the tranny and timing belt stuff. In order to smash the plugs something had to be in there. The pistons didn't reach them on there own. That would have made quite a bit of noise lol. Also because you had 3 and not one smashed plug we can assume whatever got in there it happened in the intake and was distributed over multiple cylinders. So think stuff rather than "it"? When you dropped rpms vacuum increased. More pull for junk? So next question... if you suddenly smashed 3 plugs what would happen? Might just stop pretty quick. But seize? Not sure about that. Maybe chain reaction into some other part.

Somewhere along the line somebody left some stuff in the intake, carb or heads and it got processed. That made things very unhappy. Thats my guess. Why didn't it happen immediately. Who knows?

I would pull it. Take it all apart and see whats up. At this point what have you got to lose.

[Formulajones]

Sorry to hear about the mishap.

Spark plugs closed says something was floating around.

I'm assuming this thing has flat top pistons in it. The only time I've ever had a piston close a plug gap was with a dome piston.
The last 454 I spun a couple rod bearings in was so bad the piston was smacking the bottom of the cylinder head, and actually marked up the top of the piston. Never touched the spark plugs though, because it had flat tops in it. You would need to have a plug that actually stuck down below the entire combustion chamber for a flat top to touch it, and I've just never seen that.

Most Pontiac builds seem to have either flat tops or dished pistons so my feeling is the plugs weren't closed by the piston itself, but likely some foreign object that got in the combustion chamber. I would expect to see a mark (or 2) on the ground strap from contacting something as well.

[PunchT37]

Originally Posted by Formulajones

Sorry to hear about the mishap.

Spark plugs closed says something was floating around.

I'm assuming this thing has flat top pistons in it. The only time I've ever had a piston close a plug gap was with a dome piston.
The last 454 I spun a couple rod bearings in was so bad the piston was smacking the bottom of the cylinder head, and actually marked up the top of the piston. Never touched the spark plugs though, because it had flat tops in it. You would need to have a plug that actually stuck down below the entire combustion chamber for a flat top to touch it, and I've just never seen that.

Most Pontiac builds seem to have either flat tops or dished pistons so my feeling is the plugs weren't closed by the piston itself, but likely some foreign object that got in the combustion chamber. I would expect to see a mark (or 2) on the ground strap from contacting something as well.

My thoughts too. I would think a piston would hit the head 1`st, and the plug would be further up in the chamber.

[ponjohn]

Pull the heads off now while waiting for help.

[wbnapier]

More photos.

It's hot, and I'm tired. I could do better photos, but I need a break.

Note the vertical striations in one bore.

I cracked number 8 rod cap loose and I was able to move the piston.

Here's what more I have...

[Brian Baker]

I'm hoping the "smashed" plugs is just some weird anomaly and when you open it up you find something really simply, weird and stupid...like the oil pump shaft broke and wedged itself on one of the crank throws. I know...far fetched, but...

[johnta1]

like the oil pump shaft broke and wedged itself on one of the crank throws. I know...far fetched, but...

I've had that happen, broke the 'hole' in the block where the shaft goes through.

Look down the distributor hole and see what it looks like?



So many things can be the problem, maybe it will be a new one for us?



(but hopefully not an expensive one)

[400 Lemans]

I've seen that happen too. Pump shaft busted out of its block hole. It looked like a pretzel caught up in crank and locked the engine down.