[wbnapier]

Thanks to Tom S for going to the shop and documenting things with the machinist.

I just spoke to the machinist. Yes, there was some sort of crank radius problem or bearing failure on #5. Friction, heat, seizure...

He measured endplay again and it was perfect. 6-8 thousands I think he said.

He says that no regular guy can be expected to see or know this would be a problem.

He is going to take all sorts measurements of the Scat crank vs. a stock Pontiac crank radius and those bearings to let me have technical info on the specifics of the failure.

The crank is repairable with a 10 under grind. The radius (fillet) will need to be reduced or a different bearing used that is narrower or has an appropriate chamfer.

The block is likely salvageable, but will need some work. Yes, it looks like a chunk broke off in the picture, I forgot to ask. That is for Monday.

Regarding cleanliness of my assembly area. During assembly, I was constantly texting him with questions and photos. He noticed that I was working in my garage and sometimes in the driveway and didn't like that. I agree, but had no choice. He doesn't believe dirt or debris played any role in this failure.

I'm waiting on Monday, then I need to contact Butler with the info about the crank and/or bearings and see where I am.

Frankly, between the machinist and Tom, they've communicated that I didn't f**k it up, which is a relief. I can live with myself.

[mchell]

Those dowel pins have anything to do with the failure?

[tom s]

None at all,the block was line honed after they and the ARP bolts were put in.Pretty sure its something to do with the radius on the aftermarket crank and the bearing.Tom

[mchell]

Weird.... So you’re thinking it’s a manufacturing flaw? Those scat rotating assemblies are usually darn nice.

[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.

[Mike Davis]

What was the mfg of the bearings? I had a two sets of Clevite bearings here last year and one set was almost .018 wider than the other. I started checking all of them I install now and also radius the sides of all the bearings with a hand debur tool.

[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..

[Formulas]

Was the rear seal already taken out before the pic?
Or a camera shadow thing?

The heat also seems to be quite a bit forward of the slinger radius enough to turn blue in the oil groove. Seems if it was as simple as bearing riding slinger radius it would clearance itself quickly on break in then cool and would also affect end play on assy

I once burned a rear main bearing I suspected it was from a -8 oil line ( to small ) to cooler / filter on a long high speed run went to -10
15 years before interweb

.

[tom s]

Aftermarket cranks are famous for having a large radius.They make narrow rod bearing for them.As said I had a slight issue with a rear main when I took a engine down.The very back was in the brass but nothing like this.Was never enough to even feel it when the crank was turned without the seal.Just something to be aware of when using aftermarket cranks.When I got there today all the caps were off.Im sure the seal was toast with the heat that crank and bearing saw.Tom

[tom s]

I tried to post a pic of the block saddle but wont post for some reason.The seal just melted out of it.The clevite left a imprint in the saddle that you can feel with your finger nail.Maybe it will show up as I did the down load like I did the rest.Im sure Mike will get some more info for us next week as he is REALLY interested.tom

[Baron Von Zeppelin]

Yeh it roasted the 1 piece rear main seal.
A little surprised it didn't make an oily mess back there with it being out of commission ?
Maybe some of the desintegrated seal debris plugged up some oil flow.

Something caused #4 thrust to turn in the cap
And then there's the scuffing in the cylinders that might have been lack of oil

... and the spark plug gaps that are another enigma unto themselves.

Im sure Mike will get some more info for us next week as he is REALLY interested.tom

That is really great to hear he is taking high interest in it.

[tom s]

The 4 cap did not turn!Optical illusion !All other bearings are fine.Tom

[tom s]

Try one more time.

[tom s]

There you go!

[Baron Von Zeppelin]

Dabgummit . lol
In Napier's pics before disassembly, and your pics after crank removed - it looks to be turned out of index in all those pics. (#4 thrust)

The other shells in your pics are still indexed proper.
You got me !
victim of circumstance and opticals !
The #4 surfaces didn't really look bad - i believe you

[hgerhardt]

Originally Posted by tom s

Pics

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

[wbnapier]

The bearings were Clevite Performance, either P or H. My invoice doesn't say which, I can't remember. Both the machinist and Tom are very confident in the diagnosis.

I see damage to the block in one of Tom's photos (attached and circled in red).

Curious what you all think of the block damage and the blocks future prospects.

The spark plug thing is a mystery.

There wasn't a drop of oil leaking. 6.5+ quarts in the engine.

[wbnapier]

Originally Posted by Mike Davis

What was the mfg of the bearings? I had a two sets of Clevite bearings here last year and one set was almost .018 wider than the other. I started checking all of them I install now and also radius the sides of all the bearings with a hand debur tool.

Clevite also. You are more observant than me. Smart move.

[MarkS57]

Just a thought, were the bearings supplied by Butler with the rotating assembly? If it is a journal radius issue wouldn't some culpability belong to Butler?

For the spark plugs, is it possible the center electrode broke inside the insulators and dropped down to close the gap? Crazier things have happened.

[wbnapier]

Originally Posted by MarkS57

Just a thought, were the bearings supplied by Butler with the rotating assembly? If it is a journal radius issue wouldn't some culpability belong to Butler?

For the spark plugs, is it possible the center electrode broke inside the insulators and dropped down to close the gap? Crazier things have happened.

Yes, the bearings were part of the kit I purchased from Butler. I will try to speak with them Monday, but I'm waiting on more info from the machinist. He's going to do some measurements with different bearings, stock crank, etc..

In my opinion, they should sell the kit with a narrow bearing or reduced radius (fillet). The customer should have no need to machine the crank for this. At the least, send a note with the kit that this needs to be checked.

Also, I wouldn't be surprised if this is either a manufacturing defect by Scat or Clevite. I doubt Butler would even check something like this on their own builds,

This cannot be a normal thing, otherwise garage hobbyists are doomed. If a hobbyist needs to go to this level of inspection detail on semi-finished parts, it becomes an unworkable project for most of us.

Moving forward, I would caution anyone against purchasing their own parts and doing this. Let your machinist prepping your block purchase the parts and have responsibility for them.