[RWS]

My guess is that the timing chain broke, which meant that a number of pistons hit open valves.

That happened to me long ago at about 50 k miles, and it required a total rebuild (albeit with no damage to the block, crank, or rods).

[SRR]

How was the block cleaned before final assembly? I got a block back from a machine shop once and was told "Just put it together" I elected to clean all the oil passages with brake clean and brushes. Lot's of dark gritty stuff came out. I did have a new engine once develop a rod knock after only a few miles and when I pulled the pan there was a pile of black gritty stuff in a small pile under the bad rod...expensive lesson on final cleaning.

The only reason I ask is because I think I see some black debris in your oil pan?

[hgiv]

That was my thought. If had some head work maybe there was stuff in there which didn't initially come through. Maybe once hot or higher RPM? Then it almost instantly knocked out 3 plugs and all sorts of trouble happened. Of course I have no idea if 3 bad cylinders could then cause the other damage or things to seize? I mean... a bad electrical situation could cause the same thing. That wouldn't kill everything.

Also we don't know that it's seized... it just won't turn. Not same thing.

[lust4speed]

Were the dowel pins put in prior to the line hone?

[tom s]

I dont think anyone has pointed out what the issue might be yet!Tom

[Scarebird]

Tom is right. Only disassembly will show the issue here.

[steve25]

Wow! 10 minutes of main Bearing run time on just assembly oil is a bit more then I would have thought.

[mgarblik]

The ten minutes was an estimate, I was not there. Could have been 6-7 minutes. It ran at steady speed breaking in the new camshaft. I guess break-in lube, no to little load, and some splash lube kept it going for a while.

[tekuhn]

I’m anxious to hear the assessment of the crank journal. I have a forged Scat 4.25” myself, although it’s for 3” mains. Still in the box, but I will go over it with the proverbial fine toothed comb.

[mgarblik]

I have seen allot of Pontiac engine failures over the last 40+ years but NEVER a failure on the #5 main bearing alone. That is a bizarre failure and I am sorry you had to be the one to have it happen. I am also sorry to hear a Scat forged crank may be the cause because I am building an engine with one as well. Disappointing situation for sure but it looks like you have a good shop dealing with it and it will be corrected.

From the few pics provided, it looks like the oil slinger area and the radius is the problem. It looks like the slinger is not riding in the center of the groove and has little radius. If it was rubbing in the block or cap that would make allot of heat and ferrous debris quickly..

[Schurkey]

Originally Posted by steve25

Wow! 10 minutes of main Bearing run time on just assembly oil is a bit more then I would have thought.

Auto Mechanics Class graduation picnic.

A Mopar got dragged out of a Treasure Yard, drained of oil, and idled. Bets taken on how long before it "blew up".

When folks got bored, they put a brick on the gas pedal, not enough to achieve WFO, but beyond "fast idle".

Most folks went home before it seized.

God bless the Leaning Tower of Power.

[GTOEARL]

Been following your post and your issues here. My heart goes out for you buddy. Waiting patiently for the results. I hope it’s not too bad. I admire your courage in putting the motor together.

[tom s]

Pics

[tooski]

Looks to me like a chunk missing at the red circle. Perhaps that's where the tang sits. Also the grooves on this side looks to me to be a bit shorter than the grooves on the other side; as if the saddle was bored too much to one side

[hgerhardt]

Originally Posted by tom s

Pics

nevermind what I just said. Man, that made a mess.

[Formulas]

Is the oil groove restricted by foreign material?
Local bearing starvation?

Doesn't seem to be located in the block properly wheres the tang at cant see it on me cell phone

One thing I do on assy is after every addition to the engine assy every bearing cap every rod cap I spin it to make sure there is no large increase of torque or binding

[tom s]

the bearing was tight at the very rear and as it heated up the heat transferred to the front of the bearing where the very front still has coating.The autopsy has just begun as the radius on the crank really does not look wider than a stock 455 crank.As said before the owner supplied all the parts from a 3rd party and did the assm himself.Mike was a little concerned as the engine did not look like it was assm in a very clean room.So far nothing has been found that the owner did anything wrong.I think the issue has something to do with the after market crank and the Clevite bearing.I had a engine with a little copper showing at the very back edge of the rear bearing but nothing like this.Tom

[tom s]

I forgot to ask about the spark plugs!Tom

[Scarebird]

Why would the crank be heat blued at the oil feed grooves?

Would a foreign substance heat up if pumped into the oil grooves? Did the rod bearings show the same thing?

[tom s]

Bearing was welded to the crank,had spun.Tom