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Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
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PostPosted: Fri Jul 17, 2020 10:12 pm 
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I'm reasonably lucky that I have access to this place to work on precision stuffs.

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Coated block:

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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.

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Mic'ing a whole lotta bores...

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

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

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PostPosted: Sun Jul 19, 2020 1:50 pm 
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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 to reduce clearance... But not having much luck.


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PostPosted: Mon Jul 20, 2020 11:35 am 
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Mark, do you have any experience with shimming bearings?

I'm looking at this product: http://deckwartaperedshims.com/main-bea ... t-info.php
I emailed them asking if they knew of their product being used in engines turning >8000 RPM and making 100 HP/liter or more.

To start with, my current clearance is 0.0035, which is usable, but outside of spec and wider than I want to be.
In either the 0.001 or 0.002 thickness. I'd put it under the bottom bearing shells only. A 0.001 shim would get me down to 0.0025 clearance, which is within spec. A 0.002 shim would get me down to 0.0015, which is on the tight side of where I'd like to be. I think I want to be just under 0.002 clearance.

I think I should post this at Speed Talk as well.


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PostPosted: Mon Jul 20, 2020 12:46 pm 
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Having built many engines, I can see where this solution would be possible. I am skeptical in a high performance, high rpm situation.
I am not saying it won't work, I am just undecided I guess. I could see using it on a 355 with cam drive gear mesh issues due to line honing.
I see no reason for it not to work. For $52 what is there to loose, just buy some and see how they fit and measure out.
I am interested and will be watching your progress.
Oh, I think less than .002 on the clearance is too tight.

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PostPosted: Mon Jul 20, 2020 1:34 pm 
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0.002 is snug... but it's an aluminum block AND aluminum bedplate; although the bearing shells are steel, so as the block heats up, they'll probably just lose crush more than increase clearance


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PostPosted: Wed Jul 22, 2020 11:17 am 
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I don't know....putting it under the bottom only seems a mistake as the sides of the top bearing will to too loose right?

When I was putting mine together I didn't like the bearing clearance and used this stuff
https://www.calicocoatings.com/coating- ... lubricant/

its 2.5-3 tenths thick so 1/2 thou on the diameter and call it good enough? The rule for race engines is better loose than tight, you can always up the oil viscosity if loose but tight means spun bearings. also stuff moves and flexes, normally when you increase the rpm, increase the bearing clearance, 0.002 seems too tight for race engine mains.


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PostPosted: Thu Jul 30, 2020 9:03 am 
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I already have the standard Calico coating on the bearings, so I can get another set of bearings and install uncoated if the clearance turns out tight.

I dropped the lower crankcase/bedplate off at the local prototype machinist I've been using. He has a fly cutter and will skim 0.002 off the mating surface. That should get the main bores on my block down to the diameter of the main bores on the first block (which had pitted cylinder bores). That block would have 0.0025 clearance with the same bearings, so I'm optimistic this will work out.

I posted this topic at Speed-Talk:
https://www.speed-talk.com/forum/viewto ... 15&t=61699

One guys says if you use shims, you'll see the edge of the shim in the wear pattern on the bearing.

Calico says they can coat up to 0.0006 coating thickness. Line2Line says they can coat thicker... the rep didn't have an issue when I asked if there was a technical reason to get both shells coated at 0.0007 or one shell coated 0.0015.


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PostPosted: Sun Aug 09, 2020 11:36 pm 
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Oh yeah... After consulting the brain trust at SpeedTalk and considering that the block I'm going to use has main bores 0.002 larger than the main bores in the block with pitted cylinder bores, and that the block with pitted cylinder bores would have main clearance right at 0.0025... I decided the best solution would be to skim the lower crank case 0.002 to reduce the main bore ID. So I dropped it off with the prototype machinist a couple of weekends ago.


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PostPosted: Mon Aug 10, 2020 7:23 am 
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TheDarkSideOfWill wrote:
Oh yeah... After consulting the brain trust at SpeedTalk and considering that the block I'm going to use has main bores 0.002 larger than the main bores in the block with pitted cylinder bores, and that the block with pitted cylinder bores would have main clearance right at 0.0025... I decided the best solution would be to skim the lower crank case 0.002 to reduce the main bore ID. So I dropped it off with the prototype machinist a couple of weekends ago.


Its the right general idea but if the bores are round now then the result will be bearing bores that are about .002 out of round. You can do a CAD model or excel sheet to figure out exactly what you'd need to remove to get round holes .002 smaller....probably about .010 from each surface would be my guess. Still, I guess the result will be on average 1/2 better than you have now.


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PostPosted: Mon Aug 10, 2020 7:26 am 
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mk e wrote:
TheDarkSideOfWill wrote:
Oh yeah... After consulting the brain trust at SpeedTalk and considering that the block I'm going to use has main bores 0.002 larger than the main bores in the block with pitted cylinder bores, and that the block with pitted cylinder bores would have main clearance right at 0.0025... I decided the best solution would be to skim the lower crank case 0.002 to reduce the main bore ID. So I dropped it off with the prototype machinist a couple of weekends ago.


Its the right general idea but if the bores are round now then the result will be bearing bores that are about .002 out of round. You can do a CAD model or excel sheet to figure out exactly what you'd need to remove to get round holes .002 smaller....probably about .010 from each surface would be my guess. Still, I guess the result will be on average 1/2 better than you have now.



.010? should that be .001?

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