Bearing clearance problem LQ4
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Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
Bearing clearance problem LQ4 So I just picked my block (2002 LQ4) and crank up from the machine shop. And now I'm assembling the bottom end. It is a stock crank and the shop recommended King XP bearings (going TwinTurbo). The crank was just cleaned and balance for the new assembly and the bearings are standard size for the LS engine. But when I Plasti-gauged the mains today, I'm getting readings of .001 and slightly wider. I re-checked and got the same readings. Just wondering if I'm doing something wrong. Seems to be a really tight fit for everything being stock. Do these bearings tend to fit tighter? Thanks.
Thread Starter
Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
Are the plasti-gauges usually off? I am heading over my dads now to grab a micrometer to measure the crank and main journals. I figured that way I'd have some proof for the shop if the numbers are off. I did pay them to check everything and recommend a bearing. So we shall see
Thread Starter
Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
So I measured the mains with the bearings in and no crank and the space was consistently at 2.557". The crank journals measures at 2.560 (1), 2.559"(2), 2.560(3,4,5). So it looks like the crank is too big for the bearings.
What's the full part number for the bearings?
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Was this block bored/honed and if so how did the machine shop clean this block before said procedures ??
I use shops that acid dip which removes ALL porosity from the coolant passages
Many shops still "bake and tumble" and I've seen way too many instances where a crank that came out if an engine won't turn or turns too tight after the shot tumbling process tightened up the main bores. Thus crushing the bearing shells too tightly. These blocks need a kissing from a line hone for the mains to be correct spec again
I use shops that acid dip which removes ALL porosity from the coolant passages
Many shops still "bake and tumble" and I've seen way too many instances where a crank that came out if an engine won't turn or turns too tight after the shot tumbling process tightened up the main bores. Thus crushing the bearing shells too tightly. These blocks need a kissing from a line hone for the mains to be correct spec again
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Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
Thread Starter
Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
Was this block bored/honed and if so how did the machine shop clean this block before said procedures ??
I use shops that acid dip which removes ALL porosity from the coolant passages
Many shops still "bake and tumble" and I've seen way too many instances where a crank that came out if an engine won't turn or turns too tight after the shot tumbling process tightened up the main bores. Thus crushing the bearing shells too tightly. These blocks need a kissing from a line hone for the mains to be correct spec again
I use shops that acid dip which removes ALL porosity from the coolant passages
Many shops still "bake and tumble" and I've seen way too many instances where a crank that came out if an engine won't turn or turns too tight after the shot tumbling process tightened up the main bores. Thus crushing the bearing shells too tightly. These blocks need a kissing from a line hone for the mains to be correct spec again
The Plastigauge is not as accurate as a mic and dial bore gauge with .0001" increments, but it's better than nothing. Usually the standard bearings are a little tight, but it shouldn't be an interference fit. You may have to swap the MB5013XP bearings out for a set of MB5013XPSTDX bearings to get your clearance where you want.
Thread Starter
Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
Usually the journals on the crank are within .0001", especially the GM cranks. It's the mains that are usually inconsistent just because it's very difficult to line hone to the same consistency as grinding the crank.
The Plastigauge is not as accurate as a mic and dial bore gauge with .0001" increments, but it's better than nothing. Usually the standard bearings are a little tight, but it shouldn't be an interference fit. You may have to swap the MB5013XP bearings out for a set of MB5013XPSTDX bearings to get your clearance where you want.
The Plastigauge is not as accurate as a mic and dial bore gauge with .0001" increments, but it's better than nothing. Usually the standard bearings are a little tight, but it shouldn't be an interference fit. You may have to swap the MB5013XP bearings out for a set of MB5013XPSTDX bearings to get your clearance where you want.
Main Journals mic out at 2.559. Bearings torqued down mic out at 2.560. Which is pretty close to the reading I was getting with the plastigauge of .001. I also just mic'd the rods and bearing. Crank journal was 2.100, rod opening was 2.223. The bearing width was .068. So that tells me they'll be too tight as well. If I did that correct. Rod bearings are King CR807HPN. Thanks for all the advice.
Thread Starter
Staging Lane
Joined: Jan 2016
Posts: 79
Likes: 4
From: Delaware
So I bought an calibrated a new Mike set and here's what I got
King specs. 2.7509/2.7514. 2.5588/2.5593. .192. .0001/.0006
Main cap/ Housing diameter/Crank diameter/Bearing clearance/Total Clearence
1. 2.7475/ 2.5588/ .192/ -.0033
2. 2.7460/ 2.5588/ .192/ -.0048
3. 2.749/ 2.5588/ .192/ -.0018
4. 2.7505/ 2.5588/ .192/ -.0003
5. 2.749/ 2.5588/ .192/ -.0018
Looks like the main caps are too tight and probably need to be line honed. I do have a question though. On Kings website, if the crank and mains fall within the peramiters they set. The clearance ranges from .0001-.0006, which still seems very tight. Am I calculating this incorrectly?
King specs. 2.7509/2.7514. 2.5588/2.5593. .192. .0001/.0006
Main cap/ Housing diameter/Crank diameter/Bearing clearance/Total Clearence
1. 2.7475/ 2.5588/ .192/ -.0033
2. 2.7460/ 2.5588/ .192/ -.0048
3. 2.749/ 2.5588/ .192/ -.0018
4. 2.7505/ 2.5588/ .192/ -.0003
5. 2.749/ 2.5588/ .192/ -.0018
Looks like the main caps are too tight and probably need to be line honed. I do have a question though. On Kings website, if the crank and mains fall within the peramiters they set. The clearance ranges from .0001-.0006, which still seems very tight. Am I calculating this incorrectly?
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Joined: Jan 2025
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So I bought an calibrated a new Mike set and here's what I got
King specs. 2.7509/2.7514. 2.5588/2.5593. .192. .0001/.0006
Main cap/ Housing diameter/Crank diameter/Bearing clearance/Total Clearence
1. 2.7475/ 2.5588/ .192/ -.0033
2. 2.7460/ 2.5588/ .192/ -.0048
3. 2.749/ 2.5588/ .192/ -.0018
4. 2.7505/ 2.5588/ .192/ -.0003
5. 2.749/ 2.5588/ .192/ -.0018
Looks like the main caps are too tight and probably need to be line honed. I do have a question though. On Kings website, if the crank and mains fall within the peramiters they set. The clearance ranges from .0001-.0006, which still seems very tight. Am I calculating this incorrectly?
King specs. 2.7509/2.7514. 2.5588/2.5593. .192. .0001/.0006
Main cap/ Housing diameter/Crank diameter/Bearing clearance/Total Clearence
1. 2.7475/ 2.5588/ .192/ -.0033
2. 2.7460/ 2.5588/ .192/ -.0048
3. 2.749/ 2.5588/ .192/ -.0018
4. 2.7505/ 2.5588/ .192/ -.0003
5. 2.749/ 2.5588/ .192/ -.0018
Looks like the main caps are too tight and probably need to be line honed. I do have a question though. On Kings website, if the crank and mains fall within the peramiters they set. The clearance ranges from .0001-.0006, which still seems very tight. Am I calculating this incorrectly?
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