Large(ish) Main Bearing Clearance
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Teching In
Joined: Mar 2025
Posts: 28
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From: Northern Wisconsin
Large(ish) Main Bearing Clearance I’ve got a LQ4 block and crank that are in great shape, but it appears that out of the factory they are/were extremely close to the tolerance extremes. After crank polishing and align hone, I’m at the very max for bearing clearance…one journal is even a hair bigger.
My question is: In a slightly higher performance engine (550hp) can I maintain a better oil film strength with a slightly heavier oil and a high volume and pressure pump?
My question is: In a slightly higher performance engine (550hp) can I maintain a better oil film strength with a slightly heavier oil and a high volume and pressure pump?
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
I’ll have to get my measurements later this evening and post them. I measured the crank journals and main bores before and after bearings installed and caps torqued.
I want to say I’m in the .00275 - .003 range. I’ll have to get exacts when I’m looking at my notes when I get home.
I used a Starrett dial bore and also compared with telescoping gauges also.
I want to say I’m in the .00275 - .003 range. I’ll have to get exacts when I’m looking at my notes when I get home.
I used a Starrett dial bore and also compared with telescoping gauges also.
Thread Starter
Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
I stupidly bought extra clearance bearings originally without having a better understanding of clearances (or engine building). I have since installed Standard Size coated King bearings to end up at my current situation.
The extra clearance was way way out to lunch I discovered right away.
The extra clearance was way way out to lunch I discovered right away.
I stupidly bought extra clearance bearings originally without having a better understanding of clearances (or engine building). I have since installed Standard Size coated King bearings to end up at my current situation.
The extra clearance was way way out to lunch I discovered right away.
The extra clearance was way way out to lunch I discovered right away.
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Joined: Feb 2018
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From: Michigan
I would try to get it a little tighter like others suggested. That said, my mains in my LS7 are set about 0.0024 to 0.0027, and being that it's an aluminum block, it will expand a bit more.
I run a Katech LS9 oil pump with 20w-50 oil and it has been good so far, over 100 psi of oil pressure at 7000 rpm when the oil is 200+ degrees.
I run a Katech LS9 oil pump with 20w-50 oil and it has been good so far, over 100 psi of oil pressure at 7000 rpm when the oil is 200+ degrees.
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Teching In
Joined: Mar 2025
Posts: 28
Likes: 5
From: Northern Wisconsin
I finally dug through my notes and found my measurements-
1) .0027
2) .0027
3) .0035
4) .003
5) .0032
These are with the King Coated Main Bearings installed.
I’m thinking (hoping) 10w-40 with the Melling high volume and pressure pump is going to keep the oil film strength in the survivable range.
I’ve definitely learned so far that I’m going to have to show up at the machine shop with specific instructions as to what I need them to accomplish.
1) .0027
2) .0027
3) .0035
4) .003
5) .0032
These are with the King Coated Main Bearings installed.
I’m thinking (hoping) 10w-40 with the Melling high volume and pressure pump is going to keep the oil film strength in the survivable range.
I’ve definitely learned so far that I’m going to have to show up at the machine shop with specific instructions as to what I need them to accomplish.
Jesus, fire your machinist. He total fubared that line hone. It will survive, but trust me, go Mobil 1 15w-50. Just trust me, been down this road so many times.
Do this:
Melling 10295 w COPO spring and the 15w-50 and it should be ok. If the machinist screwed up the line hone that bad, I would absolutely look at and measure the cam bearings. If those are way off, don't even build it, fix the issues first because it will be a never ending nightmare once running.
Do this:
Melling 10295 w COPO spring and the 15w-50 and it should be ok. If the machinist screwed up the line hone that bad, I would absolutely look at and measure the cam bearings. If those are way off, don't even build it, fix the issues first because it will be a never ending nightmare once running.