[wbnapier]

Hot, soapy water. Acetone, mineral spirits, etc... I had one of those engine brush cleaning kits, Maybe a missed something. We'll find out.

The first oil filter was really clean after initial start and the second oil filter was pretty clean after failure.

[hgerhardt]

And none of the recent posts address the rotated/spun main bearing that we already know of. My guess is he installed that bearing with the oil hole down which caused that bearing to run dry and seize. With only light load, the rod bearings could have been OK since the rods share common crank pins and would have gotten some oil from the mains that did get oil.

[dataway]

Curious ... how much run time was on the engine before it saw it's first shake down drive on the street? Was the street drive the first time it saw any substantial rpm?

[wbnapier]

Originally Posted by dataway

Curious ... how much run time was on the engine before it saw it's first shake down drive on the street? Was the street drive the first time it saw any substantial rpm?

I had it idle two times, for about 15-20 minutes each time in my driveway. Then I drove around the block, maybe 3 mins.

Yes, this was the first real drive with any RPM. I got up to 4K on the freeway.

[F ROCK]

one bad lifter can leave alot of metal

I hope there is minimal damage

[61-63]

You may have answered this or stated it somewhere above but did you use plastigauge on every main journal when you put the thing together? I'm asking for my own benefit here. I've put a couple of Pontiac engines together but not a nice one like that. But am about to. I really feel for you man!

[wbnapier]

Originally Posted by 61-63

You may have answered this or stated it somewhere above but did you use plastigauge on every main journal when you put the thing together? I'm asking for my own benefit here. I've put a couple of Pontiac engines together but not a nice one like that. But am about to. I really feel for you man!

Yes, I used plasti-gauge. I know it gets a bad rap by some, but it is user friendly. I have a set of outside micrometers and a dialbore gauge, but the plasti-gauge was easier.

[dataway]

Whatever happens ... don't be discouraged about assembling an engine. Although, the farther an engine is removed from a stock condition, the more experience and expertise is needed. Not just because aftermarket parts have quirks that experience will spot, but because the engine is going to be stressed beyond it's designed range and that usually requires an additional level of knowledge and attention.

Personally I'm pretty confident assembling a stock engine but when HP gets up above 450 these engines become a different animal that requires a different skill set. When you find out what the problem was ... dive right back in and make it right. Although you can put me in the micrometer camp .... I can't get plastigage to work for sheeet.

[tekuhn]

Any possibility you forgot to torque the #4 main cap? With the visible gap between the cap and block it seems like you would have heard something if it broke enough to have that much gap with it fully torqued. That or perhaps the cap hung on the alignment stud or something was trapped underneath? All just guesses, of course. Sure sounds like you did everything right and it's certainly a high quality build overall. It sure sounds like you knew what you were doing. I hope the mystery gets solved. I think you'll regret selling the car down the road, so don't rush into that decision. Hang in there...

[HWYSTR455]

I don't think there's a gap there, think it's an illusion, due to a slight build up of oil at the parting line.


.

[tekuhn]

Originally Posted by HWYSTR455

I don't think there's a gap there, think it's an illusion, due to a slight build up of oil at the parting line.

I wondered about that and hope you're right.

[tekuhn]

---

[GTOEARL]

Read every entry in this blog. Very interesting information and very unfortunate for you. I hope it’s an easy fix. Obviously you’ve heard from a lot of people and a lot of different scenarios of what might’ve happened. Hopefully it’s a spun bearing that allowed the crank to move just a bit to kiss those spark plugs.. The very best of luck for you in solving this issue..

[NeighborsComplaint]

Originally Posted by GTOEARL

Read every entry in this blog. Very interesting information and very unfortunate for you. I hope it’s an easy fix. Obviously you’ve heard from a lot of people and a lot of different scenarios of what might’ve happened. Hopefully it’s a spun bearing that allowed the crank to move just a bit to kiss those spark plugs.. The very best of luck for you in solving this issue..

How does the crank move with a spun rod bearing? It's upward travel is limited to the normal stroke plus the main bearing clearance which is restrained by the main cap. Even with a single main bearing failure, the unsupported part of the crank between adjacent bearings does not deflect enough to allow a piston to contact the combustion chamber.

As regards theory that a flat top piston can hit the spark plugs, try this at home: Screw a spark plug into a cylinder head. Turn the cylinder head upside down and and place a flat top piston on the deck. What does it do? It sits nice and flat on the deck without getting anywhere neat the sparkplug.

My current 455 motor was drag raced and had 670 heads with Venolia pop-up piston domes. The motor had repeatedly spun a rod bearings and the owner gave up and had the motor disassembled. Every piston had a ding in the corner of the dome from contacting the edge of the combustion chamber due to interference as a result of the block being decked too severely. Even with spun bearings and an interference fit with the chambers, the piston domes were not hitting the spark plugs.

The pistons (3) hitting the sparkplugs and no piston to valve contact is a good story, but it doesn't add up with "no other damage other than a spun bearing and sheared cam gear keyway.

[HWYSTR455]

Aside from the plugs, the timing gear and pump shaft appear to have obvious damage.

If the crank came to a sudden stop, so would the cam, which is why I'm thinking it was the other way around, the cam came to a dead stop, crank kept moving (some), and that damaged the timing gear & pump driveshaft.

It's kind of moot, since it needs to be completely torn down, and once that happens, it will most likely be obvious what the root cause was.


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[wbnapier]

I've got the preliminary diagnosis from the machinist. Further tear down and diagnosis will be done tomorrow morning by the machinist and Tom S will be there to help as well. Many thanks to him.

I will refrain from comment here until the machinist is satisfied with his conclusion. Should be tomorrow.

If the prelim is confirmed, it will be a good lesson for all of us. It hasn't been touched on in this thread yet.

[Brian Baker]

Originally Posted by NeighborsComplaint

How does the crank move with a spun rod bearing? It's upward travel is limited to the normal stroke plus the main bearing clearance which is restrained by the main cap. Even with a single main bearing failure, the unsupported part of the crank between adjacent bearings does not deflect enough to allow a piston to contact the combustion chamber.

Think of it like this. The lower rod bearing half gets under or on top of the upper rod bearing half, decreasing the deck height. It's still possible for the pistons to kiss the ground electrode but unless they were extended plugs I think it would kiss the head first like you said.

[NeighborsComplaint]

Originally Posted by Brian Baker

Think of it like this. The lower rod bearing half gets under or on top of the upper rod bearing half, decreasing the deck height. It's still possible for the pistons to kiss the ground electrode but unless they were extended plugs I think it would kiss the head first like you said.

You missed the point of my post. The crankshaft does not cause the stroke to increase due to a rod bearing issue of any kind. What you refer to is "throwing a rod" meaning the crankshaft "threw" the rod away from the cap as a result of a rod bolt failure , The excessive clearance lets the bearing rotate and then partially "nest" one half atop the other. Nowadays, "throwing a rod" can mean any connecting rod failure, breakage or otherwise.

Again, for this to happen, a rod bolt has to fail or a bearing has to be worn through down into the shell the corresponding depth of the head gasket thickness plus deck height to allow the piston to hit the cylinder head and the plugs would still be untouched (extended tip plugs a maybe) none of which applies to the OP's motor.

[WARPATHWARRIOR]

Nice car man. Keep your chin up you're gonna get threw it get it out..Good Luck I would switch out those 48 heads for 6x-4. I might be able to help you.

[WARPATHWARRIOR]

Probably a piston to valve problem.