[STEELCITYFIREBIRD]

Was the block line honed?
Did you seat the thrust and check end play during assembly?

[wbnapier]

Originally Posted by STEELCITYFIREBIRD

Was the block line honed?
Did you seat the thrust and check end play during assembly?

Yes, but a very light line hone. Just a touch.

For seating the thrust bearing, I used a dead blow hammer and gave a couple of whacks from both sides. My machinist didn't think this was necessary and gave me an explanation of why, but I forget the details.

Yes, I measured endplay and it was withing spec, but I am at work and don't have the notes.

[mgarblik]

Originally Posted by wbnapier

Yes, but a very light line hone. Just a touch.

For seating the thrust bearing, I used a dead blow hammer and gave a couple of whacks from both sides. My machinist didn't think this was necessary and gave me an explanation of why, but I forget the details.

Yes, I measured endplay and it was withing spec, but I am at work and don't have the notes.

I am guessing your machinist said bonking the crank for and aft on a Pontiac doesn't really do anything because the main caps locate on pins, not a block register. He would be right. Many people do it on a Pontiac, but unless you have a loose sloppy fit on the pins, it doesn't really do anything.

[wbnapier]

You're right! That's what he said. I still gave a couple moderate whacks though. I figured it wouldn't hurt.

As a side note, I purchased and used those extra long dowell pins made by Precision Automotive Specialists. Both mains and head dowels were from them.

[chiphead]

Originally Posted by wbnapier

You're right! That's what he said. I still gave a couple moderate whacks though. I figured it wouldn't hurt.

As a side note, I purchased and used those extra long dowell pins made by Precision Automotive Specialists. Both mains and head dowels were from them.

Were the block's housing bore diameters checked after the line hone? My motor ended up dangerously loose (.0015" over max spec) after I swapped those same pins and had a shop line hone it. Shop said "It's fine". I said "It's not". I had to have them shave the caps again to tighten it up, to get enough main bearing crush. There is a long ugly thread about it on here.
Loose housing bores will let a bearing turn, even if the bolts are torqued to spec and the journal clearance looks OK. A turned main bearing is trying to tell you something!

[wbnapier]

Unknown. I assume so. The machinist did the light hone because I switched to ARP studs.

[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.