Crankshaft align hone?
Thread Starter
Parts Sherpa
Joined: Feb 2017
Posts: 520
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From: ICE boneyard, Pa
Crankshaft align hone?
So at what point does it affect timing chain slack? Camshaft timing? My block was bored and crankshaft polished he recommended the main caps shaved and fresh align bore back to spec shape and size. There was only one cap/main that was out but i was curious how much material does it take before this matters. I ask because this was a thread topic not long ago and there was debate about chain stretch or geometry? At what point should i be concerned?
Racer
Joined: Aug 2011
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So at what point does it affect timing chain slack? Camshaft timing? My block was bored and crankshaft polished he recommended the main caps shaved and fresh align bore back to spec shape and size. There was only one cap/main that was out but i was curious how much material does it take before this matters. I ask because this was a thread topic not long ago and there was debate about chain stretch or geometry? At what point should i be concerned?
Cap 1 .003
Cap 2 .004
Cap 3 .004
Cap 4 .004
Cap 5 .003 Oil pump torqued
Cutting double that much above could result in timing slack.
Instructor
Joined: Oct 2016
Posts: 211
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From: Raleigh NC
I think I commented in that other thread. For timing chain tension to change, the position of the crank has to change. Why would anyone "align" hone out of original factory alignment? Whoever is doing the "align" honing, should maintain the center point of the crank. When material is removed, larger bearings should take up that space and position the centerpoint of the crank right back where it was from the factory. I don't understand at all why the crank has to change position in relation to the cam or anything else just because it's bore is straightened.
Thread Starter
Parts Sherpa
Joined: Feb 2017
Posts: 520
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From: ICE boneyard, Pa
I think I commented in that other thread. For timing chain tension to change, the position of the crank has to change. Why would anyone "align" hone out of original factory alignment? Whoever is doing the "align" honing, should maintain the center point of the crank. When material is removed, larger bearings should take up that space and position the centerpoint of the crank right back where it was from the factory. I don't understand at all why the crank has to change position in relation to the cam or anything else just because it's bore is straightened.
Had a 1976 L-82, 4-sp
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From: Some days your the dog and some days your the hydrant.
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When I blew my engine years ago it was the result of oil starvation in the lower end - a couple main/rod bearings melted and two of the main caps were over heated. The machinist during the rebuild recommended an align hone, not an align bore, was needed. The align bore being considerably more expensive. Anyway, the crank journals were turned down 0.020" and oversize bearings installed. This was over 20 yrs ago and 35K miles later and the lower end of the L-82 is still holding up. No effect on the timing chain or timing.
Thread Starter
Parts Sherpa
Joined: Feb 2017
Posts: 520
Likes: 98
From: ICE boneyard, Pa
When I blew my engine years ago it was the result of oil starvation in the lower end - a couple main/rod bearings melted and two of the main caps were over heated. The machinist during the rebuild recommended an align hone, not an align bore, was needed. The align bore being considerably more expensive. Anyway, the crank journals were turned down 0.020" and oversize bearings installed. This was over 20 yrs ago and 35K miles later and the lower end of the L-82 is still holding up. No effect on the timing chain or timing.
I am just trying to not cut any corners because these parts are very hard to find in original condition. I am not doing this twice.
So my understanding is if the caps are shaved .01 (I dont know what he is doing just hypothetically speaking) then the crank moves .005 closer to the cam and introduces slack in the chain. This would also by a smaller margin reduce top end clearance? .0025ish?
Pro
Joined: May 2016
Posts: 708
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From: Minnesota
Align honing does not require machining the caps. It is a HONE, to get everything straight and to the appropriate size. Align boring involves cutting the caps first (to undersize the mains) and then bore back to the correct main size for straightness and uniformity.
As pointed out already, honing is common, boring less-so and more expensive.
"Undersize" (actually, oversized/thicker) bearings are to tighten clearances. Standard .010 or .020 under bearings are to accommodate crank undersize (NOT oversized mains - the O.D. of the bearings should be standard). Cranks are commonly ground at 10 or 20 under to clean up. In my case I used 0.001" undersize bearings on a standard crank to tighten my oil clearances after crank polishing and align honing.
There would need to be a major amount of change in the crank centerline to cause excess slack in a timing chain. I would question whether that's even a possible cause with the small dimensions we're talking about. A change of 0.020" is only 0.010" on a side. There is slack designed in the chain set to begin with, so how much slack do you have? Have you tried a different timing set? Maybe it's the tolerances in whatever set you're using.
As pointed out already, honing is common, boring less-so and more expensive.
"Undersize" (actually, oversized/thicker) bearings are to tighten clearances. Standard .010 or .020 under bearings are to accommodate crank undersize (NOT oversized mains - the O.D. of the bearings should be standard). Cranks are commonly ground at 10 or 20 under to clean up. In my case I used 0.001" undersize bearings on a standard crank to tighten my oil clearances after crank polishing and align honing.
There would need to be a major amount of change in the crank centerline to cause excess slack in a timing chain. I would question whether that's even a possible cause with the small dimensions we're talking about. A change of 0.020" is only 0.010" on a side. There is slack designed in the chain set to begin with, so how much slack do you have? Have you tried a different timing set? Maybe it's the tolerances in whatever set you're using.
Last edited by JoeMinnesota; Nov 22, 2017 at 02:16 PM.
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Melting Slicks
Joined: May 2007
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Align honing does not require machining the caps. It is a HONE, to get everything straight and to the appropriate size. Align boring involves cutting the caps first (to undersize the mains) and then bore back to the correct main size for straightness and uniformity.
As pointed out already, honing is common, boring less-so and more expensive.
"Undersize" (actually, oversized/thicker) bearings are to tighten clearances. Standard .010 or .020 under bearings are to accommodate crank undersize (NOT oversized mains - the O.D. of the bearings should be standard). Cranks are commonly ground at 10 or 20 under to clean up. In my case I used 0.001" undersize bearings on a standard crank to tighten my oil clearances after crank polishing and align honing.
There would need to be a major amount of change in the crank centerline to cause excess slack in a timing chain. I would question whether that's even a possible cause with the small dimensions we're talking about. A change of 0.020" is only 0.010" on a side. There is slack designed in the chain set to begin with, so how much slack do you have? Have you tried a different timing set? Maybe it's the tolerances in whatever set you're using.
As pointed out already, honing is common, boring less-so and more expensive.
"Undersize" (actually, oversized/thicker) bearings are to tighten clearances. Standard .010 or .020 under bearings are to accommodate crank undersize (NOT oversized mains - the O.D. of the bearings should be standard). Cranks are commonly ground at 10 or 20 under to clean up. In my case I used 0.001" undersize bearings on a standard crank to tighten my oil clearances after crank polishing and align honing.
There would need to be a major amount of change in the crank centerline to cause excess slack in a timing chain. I would question whether that's even a possible cause with the small dimensions we're talking about. A change of 0.020" is only 0.010" on a side. There is slack designed in the chain set to begin with, so how much slack do you have? Have you tried a different timing set? Maybe it's the tolerances in whatever set you're using.
Pro
Joined: May 2016
Posts: 708
Likes: 150
From: Minnesota
One thing I have also read, but not experienced personally, is that there are variations in crank-to-cam centerline evident in blocks from the factory - sometimes severe.
Your machine shop should be able to provide you an accurate cam-crank centerline measurement to decide if that's your issue.
Sounds like you don't have an issue, though, and simply asking whether align honing should be a concern? NO. Lots of us have that done as a regular part of the rebuild.
Last edited by JoeMinnesota; Nov 23, 2017 at 09:46 AM.
Melting Slicks
Joined: May 2007
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Noted. So with honing a little bit comes off of the caps. My point was that boring is a more involved/severe process than honing.
One thing I have also read, but not experienced personally, is that there are variations in crank-to-cam centerline evident in blocks from the factory - sometimes severe.
Your machine shop should be able to provide you an accurate cam-crank centerline measurement to decide if that's your issue.
One thing I have also read, but not experienced personally, is that there are variations in crank-to-cam centerline evident in blocks from the factory - sometimes severe.
Your machine shop should be able to provide you an accurate cam-crank centerline measurement to decide if that's your issue.
Le Mans Master
Joined: Apr 2001
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From: Sarver Pa
2021 C1 of the Year Finalist - Modified
I have to have my blocks line BORED when I convert 2 bolt blocks (454) to 4 bolt , then they finish up with a line HONE. Like a cylinder overbored. No you should not need a diff timing chain, I haven't.
Safety Car
Joined: Apr 2006
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From: BC
This just boggles my mind. How do you get or buy a timing chain that is a few thousand's shorter, or even why? It isn't like piston rings or bearings.
Pop Chevy is correct.This is crazy for any engine without an idler and isn't needed there either. I would be more concerned about my chain stretching a quarter inch or more from wear than a couple of thou on a line bore/hone.
Last edited by CanadaGrant; Nov 23, 2017 at 10:48 PM.
Race Director
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From: SW Florida.
Back to OP's engine. Your crank is good? Came out of this block and does not need machined? Then the main bores don't need machined either. It is really only necessary when a main bearing dies and damages the hole it sits in.
Melting Slicks
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Last edited by PAmotorman; Nov 24, 2017 at 07:48 AM.
Racer
Joined: Aug 2011
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Not exactly. Lets take a big block Chevy for instance, there is a housing bore spec for the mains, 2.937-2.938 many times the factory will go bigger than this spec, it is made up for with a over size outside diameter bearing not available to the public. When the housing bore goes outside this spec above its line hone time...if you want proper bearing crush and clearance.
The line hone/bore timing chain: The chain is not shorter, the upper gear is bigger, they come in .005 and .010 tighter and are used when the line bore/hone operator does not know how to perform this operation, or there was severe damage to the housing bore. I can get into exactly how a line hone is done if any ones interested.
Last edited by Vortecpro; Nov 24, 2017 at 08:58 AM.