[Tom Vaught]

Not much actual room (flexibility) for the crank to be in the wrong spot and not have the roll pin, distributor gear, etc see a lot of stress.

Tom Vaught

[461-69bird]

sorry Tom, I`m not understanding the answer, could you put it in simple terms for me, yes or no haha.

[steve25]

Looks like the break point started at the drill hole, likely started by a sharp edge!

[shaker455]

Originally Posted by Tom Vaught

If the block checks out you can put steel caps on the block is the block shows no other damage. Inspect the block for the oil pump shaft guide (cast in the block) still being there and in good shape.
Tom Vaught

Rick,
X2 on Tom's post....don't reuse the caps and get some steel caps.

If that's a 2-bolt block I'd consider splayed caps.

Either way sorry to see the destruction.

[johnta1]

I'd wait and see what the block looks like when tore apart.

I'd say the block is cracked somewhere in the main bulkhead.

[Tom Vaught]

Originally Posted by 461-69bird

sorry Tom, I`m not understanding the answer, could you put it in simple terms for me, yes or no haha.

Well I tried in simple terms and it was still taking too much typing so I bailed out on a reply

Tom V.

[Dragncar]

If it is a easily replaced 2 bolt block, nothing special sort of deal I would not even think about running that block again in a performance build. Could not sleep at night myself.
Sorry about your engine. But those offshore cast cranks have had issues eating thrust bearings and or failing where they should not.
I have flogged PMD cranks and never hurt one of them.

[70 bird]

Originally Posted by Dragncar

If it is a easily replaced 2 bolt block, nothing special sort of deal I would not even think about running that block again in a performance build. Could not sleep at night myself.
Sorry about your engine. But those offshore cast cranks have had issues eating thrust bearings and or failing where they should not.
I have flogged PMD cranks and never hurt one of them.

X2 I know your not in the U.S. But I would try real hard to find another block.

[Chris Uratchko]

Unless it's the picture, to me it looks like the crank was cracked for a while....

[Half-Inch Stud]

Originally Posted by RA462

I broke a factory "N" 455 crank about the same point on the track once. It was like I killed the ignition. No bang just stopped. I broke the #5 rod journal right off the crank. In our opinion the journal fillets should have been larger creating a stress concentration piont. The power from all the cylinders has to go through that #5 rod journal since the resistance on the engine is the flex plate. Just my 2 cents. Sorry about your engine.

great data point.

[taff2]

Looking at the dark areas in the crack it does appear to have started cracking a while back. Definitely got some cap fretting,what are you revving it to? And why are there main studs on only number 2 and 4 mains?
You could also do with modifying the thrust bearing, file a small chamfer along the parting lines of the shells- about 0.020" will do it. Have you restricted the oil flow to the converter/cooling circuit in the TH400? You sound like you have a recurring problem with the thrust bearing and modified TH400's are notorious for causing engine thrust bearing wear. Increased trans line pressure translates into higher cooler circuit pressure which can force the converter forward,causing thrust bearing problems.

[455firebird1969]

Originally Posted by Chris Uratchko

Unless it's the picture, to me it looks like the crank was cracked for a while....

I see what you are talking about, but I don't think they are "beach marks". I don't see a growth pattern

[twooldgoats]

Originally Posted by taff2

......
You could also do with modifying the thrust bearing, file a small chamfer along the parting lines of the shells- about 0.020" will do it. Have you restricted the oil flow to the converter/cooling circuit in the TH400? You sound like you have a recurring problem with the thrust bearing and modified TH400's are notorious for causing engine thrust bearing wear. Increased trans line pressure translates into higher cooler circuit pressure which can force the converter forward,causing thrust bearing problems.

Yes, definitely. I experienced thrust issues with my '64 GTO engine until we made these two mods.

Jim

[461-69bird]

Originally Posted by taff2

Looking at the dark areas in the crack it does appear to have started cracking a while back. Definitely got some cap fretting,what are you revving it to? And why are there main studs on only number 2 and 4 mains?



You could also do with modifying the thrust bearing, file a small chamfer along the parting lines of the shells- about 0.020" will do it. Have you restricted the oil flow to the converter/cooling circuit in the TH400?

shifting at 5500, max ever revved to 6200 but usually 5800 at finish line

don`t know about the studs, that`s how it was built. the Milodon windage tray was bolted to the studs

both of those mods were done

[i82much]

Originally Posted by 461-69bird

shifting at 5500, max ever revved to 6200 but usually 5800 at finish line

don`t know about the studs, that`s how it was built. the Milodon windage tray was bolted to the studs

both of those mods were done

I wonder if post #2 in this thread answers your question?

http://www.gtoforum.com/f50/455-main...uestion-55713/

[Half-Inch Stud]

Originally Posted by 455firebird1969

I see what you are talking about, but I don't think they are "beach marks". I don't see a growth pattern

The beach marks are a true yield strength limit indicator, yet was it organic defects in the material or a machining "stress riser" that got allowed to propagate. Hmmmmm.

[i82much]

Originally Posted by Half-Inch Stud

The beach marks are a true yield strength limit indicator, yet was it organic defects in the material or a machining "stress riser" that got allowed to propagate. Hmmmmm.

You know, I never know what the heck you are talking about, but I always get the feeling you know exactly what you are talking about.

[GTO]

Originally Posted by i82much

You know, I never know what the heck you are talking about, but I always get the feeling you know exactly what you are talking about.

LOL.

[PAUL K]

Originally Posted by i82much

You know, I never know what the heck you are talking about, but I always get the feeling you know exactly what you are talking about.

Very well said