Main bearing clearance
06-17-2010, 07:56 AM
#1
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Main bearing clearance I'm getting ready to install a Callies 383 kit in my LS1. It came with ACL race bearings, and I'm wondering about my main bearing clearances. I'm getting:
1 .00275
2 .003
3 .00225
4 .00275
5 .0025
The GM spec is .00212 max. I've got 2 LS1 books. One says .002 max, and the other says Stock to Moderate build .0021 max, Moderate to High performance build .00275 max.
I'm thinking of getting a .001 set of bearings for mains 1,2,4,5, and using them, or mixing a .001 bearing half and a std. bearing half to tighten things up.
What do you guys recommend? It's going into a Chevelle that will be summer only and street driven 90% of the time.
1 .00275
2 .003
3 .00225
4 .00275
5 .0025
The GM spec is .00212 max. I've got 2 LS1 books. One says .002 max, and the other says Stock to Moderate build .0021 max, Moderate to High performance build .00275 max.
I'm thinking of getting a .001 set of bearings for mains 1,2,4,5, and using them, or mixing a .001 bearing half and a std. bearing half to tighten things up.
What do you guys recommend? It's going into a Chevelle that will be summer only and street driven 90% of the time.
06-17-2010, 01:02 PM
#4
Well, GM spec on the main's is 0.0008-0.0021 in. for production and 0.0008-0.0025 in. for service. So your 3 and 5 clearances are on the max end 1,2 and 4 look to be too large. Being that it's going to be street driven 90% of the time, I would try to stay within factory specs for longevity. If you were building an all out race motor then those clearances might be acceptable depending on the build.
I would try and get in contact with Erik over @ HKE, he's probably one of the most respected engine builders on the boards, maybe he can give you some guidance...
I would try and get in contact with Erik over @ HKE, he's probably one of the most respected engine builders on the boards, maybe he can give you some guidance...
06-17-2010, 01:20 PM
#5
On aluminum short-blocks we will not ship them any looser than .0025" on the mains (very few exceptions to this rule). When the ACL's setup on the higher side of that range, we try a Clevite and they tend to setup a couple tenths (.0001's) tighter. Might be worth checking out!
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POWERBOND - ASP - AND MORE!
06-17-2010, 01:23 PM
#6
I shoot for .0017 - .0019 on my main bearing clearance....no more than .002 for sure.
An aluminum block will expand opening up those numbers when the engine is at temp. You wont have very good oil pressure if you set the engine up like an old school cast iron engine.
If we are discussing iron than .0024 - .0027 is probably perfect.
Note you can speak with numerous people and get numerous opinions but that is what I have used with excellent results and good oil pressure. My 383 main bearings after almost two years of abuse looked practically brand new and I honestly could have reinstalled them when I took the motor apart for a freshen up before I sold it.
Hope this helps...
-Tony
An aluminum block will expand opening up those numbers when the engine is at temp. You wont have very good oil pressure if you set the engine up like an old school cast iron engine.
If we are discussing iron than .0024 - .0027 is probably perfect.
Note you can speak with numerous people and get numerous opinions but that is what I have used with excellent results and good oil pressure. My 383 main bearings after almost two years of abuse looked practically brand new and I honestly could have reinstalled them when I took the motor apart for a freshen up before I sold it.
Hope this helps...
-Tony
06-17-2010, 01:37 PM
#7
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Thanks guys, that's what I was looking for. If I went to a .001 oversize I would be fine on 1,2 & 4, but a little tight on 3 & 5. I should be able mix half a .001 & half a standard as long as I use the same brand, right?
Measurements were taken with a mic and bore gauge.
Measurements were taken with a mic and bore gauge.
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06-17-2010, 02:34 PM
#8
-Tony
06-18-2010, 06:07 PM
#10
FormerVendor
You could run what you have and be fine but the oil pressure will be lower than normal maybe by enough at idle hot to make you worry. I would do like you said and run a half .001 to tighten it up by about .0005 and you should be fine.
It depends on what you are doing as to what you would set them at and make sure your measurements are accurate. On regular stuff we do about .002 ish like Tony and Matt said on aluminum unless it is a large power adder or an engine that will be run cold in drag race only usage.
If you end up a lil larger you can use a heavier oil like 15W50 as well and it will make more pressure and/or use the HV pumps as well. The lifters like oil pressure on the hydraulic roller stuff.
It depends on what you are doing as to what you would set them at and make sure your measurements are accurate. On regular stuff we do about .002 ish like Tony and Matt said on aluminum unless it is a large power adder or an engine that will be run cold in drag race only usage.
If you end up a lil larger you can use a heavier oil like 15W50 as well and it will make more pressure and/or use the HV pumps as well. The lifters like oil pressure on the hydraulic roller stuff.
