LQ4 bearing clearance issues
Thread Starter
Staging Lane
Joined: Mar 2024
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LQ4 bearing clearance issues I am building a LQ4 based 408 stroker and am having trouble with tight main bearing clearances. Ive tried just about every brand of extra clearance bearing and can never get more than .0015"-.0018" clearance. Thinking I need to machine the crank for more clearance I called the machine shop who did the all the machine work on the block and ask them what they recommended. They asked what my clearance was at currently and when I told him he said that .0015"-.0020" was ideal clearance for a iron block and a aluminum block and that is what they set the clearance on all the engines they build to and that I did not need to adjust the clearances at all. I personally feel that .0015" is way to tight for a iron block and just asking for trouble but would like some input on what other people think.
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Depends.
If you're building a high-RPM strip-only motor, then yeah, maybe. Especially if you're gonna use gear lube in it instead of motor oil.
You haven't told us much about this motor's purpose and future life expectations, but for anything remotely near a street kind of deal, what your machinist told you is pretty much the same as I've always used.
Another thing to keep in your mind is, clearance NEVER decreases with use, it only ever INCREASES.
If you're building a high-RPM strip-only motor, then yeah, maybe. Especially if you're gonna use gear lube in it instead of motor oil.
You haven't told us much about this motor's purpose and future life expectations, but for anything remotely near a street kind of deal, what your machinist told you is pretty much the same as I've always used.
Another thing to keep in your mind is, clearance NEVER decreases with use, it only ever INCREASES.
Thread Starter
Staging Lane
Joined: Mar 2024
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The engine is going into a 05 ctsv and will be a street car, something fun to drive on the weekends to the local "track" (long straight strip of road) and race against my buddies and maybe drive to work here and there. I would like this engine to last a while and really don't plan on adding any more power. It should make about 500whp. Would like to run 5w-30 oil in it. It has a aftermarket summit pro ls crank. I'm just afraid of getting the clearances too tight and grenading the whole engine as that's what I assume happened to the last engine that was in the car when I got it, only lasted 1000 miles lost oil pressure and spun just about every rod and main bearing.
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Then for that, those clearances should be fine.
Don't "assume" anything like that. Break that word down into its 3 components and banish it from your vocabulary accordingly. Whatever caused the last build to fail was something other than the clearances, if they were the same as these.
Don't "assume" anything like that. Break that word down into its 3 components and banish it from your vocabulary accordingly. Whatever caused the last build to fail was something other than the clearances, if they were the same as these.
With a iron block and If you're feeling uncomfortable go down to 5w20 with the tighter clearances. The trend nowadays on cars are to tighten the clearances to reduce drag on a engine resulting in more horsepower and gas mileage.
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Thread Starter
Staging Lane
Joined: Mar 2024
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Here are what my clearances are currently looking like with a set of Clevites MS2199HX bearings
1- .0022
2- .0018
3- .0019
4- .0025
5- .0019
I feel like the only ones on there that are at what I would consider good for a iron block are 1 and 4 but if everyone else thinks the clearances are good then maybe I am just afraid of some tight clearances lol. This is the first LS bottom end I have assembled have done a few SBC in the past and have never had a problem just smacking them together and letting them rip.
1- .0022
2- .0018
3- .0019
4- .0025
5- .0019
I feel like the only ones on there that are at what I would consider good for a iron block are 1 and 4 but if everyone else thinks the clearances are good then maybe I am just afraid of some tight clearances lol. This is the first LS bottom end I have assembled have done a few SBC in the past and have never had a problem just smacking them together and letting them rip.
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Verdad Gallardo TECH Addict
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They're fine. I might even say, for my own builds, looser than I'd like. In no way are they too tight. Send it. LS motors aren't that much different from the older SBC in that regard after all. (or BBC, or SBF, or Mopar, or ...)
You're only .0002-.0003" ten thousandths of and inch tighter on 3 of the clearances, I have this on file to ease your mind from K1.
https://www.k1technologies.com/k1-bl...ity-explained/
https://www.k1technologies.com/k1-bl...ity-explained/
Fireball, if you still have it torn apart, take the top shells of #1 and #4, and swap them with #2 and #5….just the top shells. That should open them up some, while making things more consistent…unless your crank journals are wonky. I have to ask you here first though…are you using Plastiguage, or are you actually measuring this with the correct tools?
Thread Starter
Staging Lane
Joined: Mar 2024
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Totally depends on the application. For a street build, what your doing is fine, although I’d have to figure out why the mains are so inconsistent. That would bother me waaaaay more than the actual clearances you have there. Race builds are different. Nitrous builds are different. You have to build the engine for the application.
Fireball, if you still have it torn apart, take the top shells of #1 and #4, and swap them with #2 and #5….just the top shells. That should open them up some, while making things more consistent…unless your crank journals are wonky. I have to ask you here first though…are you using Plastiguage, or are you actually measuring this with the correct tools?
Fireball, if you still have it torn apart, take the top shells of #1 and #4, and swap them with #2 and #5….just the top shells. That should open them up some, while making things more consistent…unless your crank journals are wonky. I have to ask you here first though…are you using Plastiguage, or are you actually measuring this with the correct tools?
TECH Apprentice
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Do you have a 24" machinist straight edge? Lay it across the main saddles with the engine upside down. Check with feeler gauges. I want to say you shouldn't have more than 0.001" gap between any of the saddles? Someone please correct me on that if that's not correct.
You said the mains spun a bearing? There's a spec somewhere for the housing bores diameters. I'd be concerned about that. How do the bearing cap surfaces look where they mate with the bearings? No discoloration or rough finish?
Edit: spun main bearings would probably require an align bore/hone, no?
You said the mains spun a bearing? There's a spec somewhere for the housing bores diameters. I'd be concerned about that. How do the bearing cap surfaces look where they mate with the bearings? No discoloration or rough finish?
Edit: spun main bearings would probably require an align bore/hone, no?
Thread Starter
Staging Lane
Joined: Mar 2024
Posts: 66
Likes: 15
Do you have a 24" machinist straight edge? Lay it across the main saddles with the engine upside down. Check with feeler gauges. I want to say you shouldn't have more than 0.001" gap between any of the saddles? Someone please correct me on that if that's not correct.
You said the mains spun a bearing? There's a spec somewhere for the housing bores diameters. I'd be concerned about that. How do the bearing cap surfaces look where they mate with the bearings? No discoloration or rough finish?
Edit: spun main bearings would probably require an align bore/hone, no?
You said the mains spun a bearing? There's a spec somewhere for the housing bores diameters. I'd be concerned about that. How do the bearing cap surfaces look where they mate with the bearings? No discoloration or rough finish?
Edit: spun main bearings would probably require an align bore/hone, no?
The block has arp studs and has been line honed. I don’t have a machinist straight edge but I will look into procuring one.