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Classic Man
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Wider than tall? I would think it was machined like that.

Taller than wide, id be more concerned about it being OOR since thats how the forces are applied to it.

With it being 5 ten thousandths out of round, is it throwing your overall bearing clearances off?

If you are really worried you could take it to the machine shop for a line bore.
 

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Discussion Starter #5
Eccentricity is built into the bearings. The bores should be round. For some reason I'm measuring huge eccentricity with the bearing installed. It's going from 20 tenths vertical clearance to 50 side to side. So I don't know what the deal is. I think the block is just over stressed from several race seasons. I doubt if anyone around here can line bore. I don't know if align honing would work especially since the oil pump center would be off.
 

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Discussion Starter #6
For future reference, I measured five blocks and found a range of 1.5-3 thousandths wider near the parting line. So I'm going say it's probably normal for a used block and not that big of deal.
 

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Discussion Starter #10
I drew up I circle (2.3228") and an elliptical "circle" in cad that is .001" wider than the circle. You would have to cut off .026" from the cap and the block to bring the parting line back into the circumference of the round circle. So align boring isn't going correct this. Chopping 2 thou off a cap and honing will do nothing if the bore is too wide.


Here is a video of the best attempt I've seen at a proper line bore. Notice the blue across the parting line when they are done. The machine didn't even touch the sides. I wonder if the bearings are just flapping in the breeze or if they actually bend and touch.

 

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Classic Man
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Here is the first good data I've found on this subject. He says that if the block is out of round it can be up to .001" at the parting line. (not vertically)

Geometrical parameters of engine bearings [SubsTech]
This is what they teach us in mechanics school as a good generic value to use. Mostly for larger pins than what a D16/D15 has, but its still a good number to use as a "ok this needs to get fixed" threshold.

Glad you updated the thread.
 

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I thought you needed a head plate or an actual head torqued down on an inline engine in order to properly line bore it?

doesnt the head squeeze the block out of shape slightly?
 

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Prelude, Integra DB9
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I thought you needed a head plate or an actual head torqued down on an inline engine in order to properly line bore it?

doesnt the head squeeze the block out of shape slightly?
We used to reckon with cast iron engines that both parts were distorted slightly, so if the block and head materials are similar, you may have a point.

Whether the 'slightly' is enough to bother about, I don't know. The bolt torque specs aren't particularly high.
 

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I drew up I circle (2.3228") and an elliptical "circle" in cad that is .001" wider than the circle. You would have to cut off .026" from the cap and the block to bring the parting line back into the circumference of the round circle. So align boring isn't going correct this. Chopping 2 thou off a cap and honing will do nothing if the bore is too wide.


Here is a video of the best attempt I've seen at a proper line bore. Notice the blue across the parting line when they are done. The machine didn't even touch the sides. I wonder if the bearings are just flapping in the breeze or if they actually bend and touch.

https://www.youtube.com/watch?v=AAWAUEnAOEM
Not a bad setup at all as Kaiser makes some really nice boring heads.


The bearings shells will bend and touch since the bearing sells need to be larger than the bearing housing bore in order to attain crush. Then again, if there bearing housing bores have too much eccentricity to being with, then the shell could possibly not attain proper crush as the circumference is larger than if the bore were perfectly round.

Depending on bearing manufacturer and the popularity of the engine, there are different bearing series with varying degrees of eccentricity. Also, there are typically oversized bearing shells available so that the bearing bore can be oversized to correct a condition like this.
 

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Discussion Starter #15
I don't know if the circumference of the bore has changed. I would expect the bore is shorter to make up for being wider. However if the bore is overall larger, then bearing crush is less.

I already called king bearings to investigate options. They do not make an oversize OD bearing. Surprise surprise. I doubt if anyone does for the D-series.
 

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I hate to bump an old thread but did you get this engine running again? Did you find bearings that account for the out-of-roundness? I have a D17 engine with the same problem; all of the main bearing clearances are .002 - .003 inches wider than tall. It's a stock daily driver so I'm not sure if I get it line bored or not.
 
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