The Mule rides again (sort of) - pics.

[The Dark Side of Will]

The Colorado block arrived... I spent the prior weekend deburring, porting the bay-to-bay breathing windows, had it cleaned at the local basic rebuild machine shop during the week, then shined it up last weekend.













Right now it's at the local custom gun shop getting Cerakoted with MC5100

My plan is to have the local race shop line bore it with the heads on, going for minimal change to the crank centerline, then take it up to ProMar in Jersey to have the bores honed and inserts installed. I'm not sure if I'll have the race shop or ProMar clean up the decks.

Then I can assemble the short block!

ETA:
I wore out a LOT of wire brushes... here's the ones I would recommend using:

Code: Select all

McMaster
PN	Short Name	McMaster Nomenclature/Description
4916A13	5/16 End Brush	Stainless Steel Brush with Shank for Tight Spaces, 5/16" Brush Diameter (1/8" shank for Dremel)
4911A79	1/2" End Brush	Brush with Shank for Tight Spaces, Long-Lasting, 1/2" Diameter with 0.01" Diameter Stainless Steel Bristles
4797A32	1.5" Wire Wheel	Brush with Shank for Angles and Corners, 1-1/2" Brush Diameter with 0.012" Diameter Stainless Steel Bristles
4797A33	2" Wire Wheel	Brush with Shank for Angles and Corners, 2" Brush Diameter with 0.014" Diameter Stainless Steel Bristles
4797A55	3" Wire Wheel	Brush with Shank for Angles and Corners, 3" Brush Diameter with 0.014" Diameter Stainless Steel Bristles

For a whole block, I recommend getting 3 of each wire wheel, 2-3 of the 1/2" end brush and about 20 of the 5/16" end brush. You'll need a die grinder to take 1/4" shank tools and a Dremel for the 5/16" end brush. The 5/16" end brush doesn't last long as it only uses 0.005 wire, while the others use tougher wire.
The 1/2" end brush is actually a really cool design; it has three plastic rings around the bristles stacked from the end of the crimped shell. As the protruding wires wear, break and bend, which would normally be the end of the brush's service life, the plastic rings protect lengths of the bristles. You can pull off one of the rings and get some more wear out of the brush; and even do that twice more since it starts with three rings. It's a cool idea.

[pmbrunelle]

Does the wire-brushed finish have enough tooth for the cerakote to bite into (vs. blasted)? Surely the gun shop has a recommendation for that?

[The Dark Side of Will]

I guess I'll find out.
Most gun applications don't get the option of a media blast. My impression is that cerakote sticks to smooth surface finish machined surfaces quite well.

ETA: the surface finish on the casting from the die casting process is sooooo smooth that I didn't want to mess it up with media blast, but I did have to deal with aluminum oxide on the surface. There were also some spots where the casting surface quality wasn't perfect, but must have been ok for GM. I did slightly more invasive work on those locations... mostly to make sure that they weren't concealing cracks.

[pmbrunelle]

What happens is that you start production with nice-looking parts, and everyone pats each other on the back for a job well done.

Then, somebody has the great idea to reduce the mold temperature, so the parts can be cooled faster, permitting a decrease in cycle time.

Then, the skin of the parts cools faster than the inside... and you have that spider web look.

[The Dark Side of Will]

Northstar had been in production for 13 years when the 2006 blocks were cast...

[ericjon262]

Porting the bay to bay ports looks like a tedious nightmare...



looks good though! how long do you think it will be with the coaters?

[The Dark Side of Will]

Yes, it is tedious. That was a 100 grit 1/2" wide x 150yd sanding strip from McMaster. They call it a sanding roll, but that has a different meaning in some circles.
I have a 36 grit roll on the way to get a bit more progress per unit time.

Since I didn't hear from the Cerakote guy this week, it should be done next weekend.

[FieroWanaBe1]

My plan is to have the local race shop line bore it with the heads on, going for minimal change to the crank centerline, then take it up to ProMar in Jersey to have the bores honed and inserts installed. I'm not sure if I'll have the race shop or ProMar clean up the decks.

Its interesting that you're having it honed with the heads on. Have you verified that torqueing the heads down affect the mains circularity or concentricity?

[The Dark Side of Will]

Yes, the mains egg by about 0.0002 when I bolt the heads on a block with the bottom end torqued. Local race shop said he could hit a 0.0005 window in bore size when line-boring and that I shouldn't worry about 0.0002. I bought 0.0005" feeler gauges and I'll do some checking on main alignment this weekend.

The bearings I had Calico coat ended up with -0.0025 clearance. I ordered another set of Clevites as I don't feel like having the crank polished down that far.

I picked up the block on Friday, but didn't have the opportunity to set it up on the stand to grab photos. It's effing beautiful. It doesn't look much different... maybe the luster is a little shinier. It feels like it's been clear coated when I touch it, though. That's what I wanted... a non-porous surface to protect the shiny. That was using Cerakote MC-5100.

I'll get to play with it more next weekend.

[The Dark Side of Will]

Also disassembled an '84-'87 rear ball joint (well... actually a U-body minivan part) to help me get some geometric data on the early style knuckles.

[The Dark Side of Will]

I was playing with the Cerakoted block last weekend... I'm seeing some weird shit.

I torqued up the bottom end and measured the main bores.
Then I bolted on the heads and measured the main bores again.
Then I split the bottom end, installed the replacement bearings, retorqued the bottom end and measured the bearing IDs.

I pulled the new set of Clevite bearings out of the box and found that the shrink wrap had ruptured and the bearings had been banging eachother up in shipment for who knows how long. They looked like they'd been media blasted in places. I polished them carefully on a veratex wheel, then cleaned and installed them. They measured out weird with a bunch of out-of-round and poor consistency from one to the next.

In looking at the numbers, I see that the Colorado block main bores are ~0.002 larger than the rusty bore block main bores in which the bearings ended up at -0.0025 main clearance. I figured that was a step in the right direction, so I split the bottom end again, installed the coated bearings and measured them. They still come up with negative bearing clearance, but it's improved from -0.0025 to about -0.0012... which is effing weird, because that's an '06 block and '06 crank... why are the bearings coming in like that?

Between the beat up set and the coated set, subtracting the bearing ID from the bore ID gave me a total shell thickness number. This is 0.3164 for the beat up bearings and 0.3170 for the coated bearings, so there's not enough variation between the bearing sets to account for the delta in bearing ID.

Once I had installed and measured the coated bearings in the Colorado block, I pulled the heads and measured them again.

I need to bolt up the bottom end on the '93 block that came out of the car and see WTF it does. I took those measurements when I built that engine, but they didn't get into my Google drive, so I may not be able to find them now. I need to check for the hard copy notes in my filing cabinet.

I also need to measure the thickness of the factory bearings that came out of the rusty bore block to see if they are different from my coated Clevites

//

When I measured the rusty bore block with and without heads, the average main bore and average out of round each increased by 0.0001. The average out of round increased from 0.00026 to 0.00038, which seems a little high.
In the Colorado block, the average main bore increased by 0.0001 and the out of round was consistent at 0.0001.

The rusty block deltas are barely worth considering and the Colorado block numbers are in the noise, so I no longer think that the mains should be bored with the heads on. If the situation evolves to the point of boring the mains 0.002 to get the bearing clearances right, this will be handy knowledge.

The average main bore in the rusty block is 2.8523 and the average main bore in the Colorado block is 2.8542. Both blocks are 2006 units. 0.0019 difference seems like a lot of variation in what should be a very consistent and precise feature.

[The Dark Side of Will]

Oh wait... I just compared the journal ODs of the cast crank that came out, the forged crank I bought new and the forged crank that came out of the rusty bore block. The crank from the rusty bore block came out at 2.5385 average, while the new forged crank and old cast crank came out at 2.5335 and 2.5338... so my used crank, that came out of a running engine is 0.005 larger than the other cranks.

That's fishy... I need to go back and make sure I didn't blow those measurements by reading the mic wrong.

[The Dark Side of Will]

I'm reasonably lucky that I have access to this place to work on precision stuffs.



Coated block:



The luster of the surface is "deeper", like it has been clear coated, but that does not show up well in photos. The whole coated surface of the block looks like this... you can see that the side of the cylinder and the head bolt boss tube looks "wet", like it has a sheen of oil... or has been clear coated. That's the coating. That a surface has been coated is immediately obvious to the touch. The coating is hard, very smooth, and actually quite slippery. I need to evaluate what the coating looks like under the heads of the "outside" crankcase to block bolts.



Mic'ing a whole lotta bores...



Valley as I was putting the (ugly, filthy) heads on my bright shiny block



Forged crankshaft with RMS weighs 50.25#, so the bare forged crank should be right at 50#.

[pmbrunelle]

Did the bearing shell thickness ever change during Northstar production?

Same bearing PNs?

[The Dark Side of Will]

Did the bearing shell thickness ever change during Northstar production?

Same bearing PNs?

My prior cranks were 2.533x on the mains. I thought the used forged crank I'd settled on using was 2.538, but it's actually 2.533. I asked the racing machine shop guy to put a mic on the crank; he called me back Saturday with the results.

So when I measured that crank, I had just finished measuring the main bore IDs in one of the blocks. Since those are 2.85XY, I was reading X off the mic barrel and Y off the vernier. I then went to the crankshaft and instead of reading 2.525+.00XY, I read 2.53XY... So I got 2.538 when I should have gotten 2.533.

So there are actually zero problems there.

HOWEVER, that means my main clearance is 0.0035ish... which is not horrible, but definitely on the wide side. Now I'm looking up bearing build-up coatings...

[pmbrunelle]

Going to build up the block side, not the journal side?

I'd be wary of building up the journal side, as there is some stackup of thin soft metal near the journal to accommodate defects, and stronger harder metal below to handle the compressive stress.

Apparently shims were a thing:
https://www.corvetteforum.com/forums/c1 ... stock.html

[The Dark Side of Will]

http://deckwartaperedshims.com/main-bea ... t-info.php

[The Dark Side of Will]

Going to build up the block side, not the journal side?

I'd be wary of building up the journal side, as there is some stackup of thin soft metal near the journal to accommodate defects, and stronger harder metal below to handle the compressive stress.

Apparently shims were a thing:
https://www.corvetteforum.com/forums/c1 ... stock.html

Sooo... these guys have a piston skirt coating that is meant to be applied to close up the piston to bore clearance a bit tight, then wear away into the exact contact pattern of the piston skirt to the bore. It's a really interesting idea, as the thickness of the coating ends up exactly matching the interface between the piston and the bore *AT TEMPERATURE* and *UNDER LOAD*... which is otherwise VERY difficult to achieve. It just wears away where the contact pressure is highest until the contact pressure is even across the entire surface.

I was hoping there was something similar available for bearings, as it should work even better in that application... although the bearing contact pressure or surface shear on cold starts or loss of oil pressure may be higher than the coating can take.

https://www.line2linecoatings.com/

http://deckwartaperedshims.com/main-bea ... t-info.php

I also sent these guys an email about the use of their product in an engine turning >8000 RPM and making >100 HP/liter.

[pmbrunelle]

I don't understand why the shims are tapered (or using a stepped approximation to a taper).

Normally, the crankcase is bored with round holes, as are the big ends of connecting rods... so I thought that the shim should simulate a smaller (circular) bored hole.

So why is the practice to make a lemon-shaped hole?

Edit: I thought about it for a bit. Since the shims are normally only added to the lower bearing caps (to avoid blocking oil passages in the engine block), the shim must be tapered towards the ends to avoid a discontinuity between the upper and lower bearing shell halves. Shimming the lower half only also keeps the upper half as fixed references, so hopefully the overall alignment between the holes remains OK.

[The Dark Side of Will]

If you put a 0.001 thick shim between each end of the insert and the block, the inside dimension across the tips of the insert decreases by 0.002. Meanwhile, if the shim is only under one of the two inserts, the inside dimension across the middle of the inserts decreases by 0.001.