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I have always used .0012" /.0016" vertical oil clearance on aluminum block, 400 Chevy main bore size and it probably requires careful and controlled warm-up.
That's actually a good way to do it. How else could you? I have done the same thing. Its amazing how much a rod for example grows on the housing bore from 2 minutes in the jet wash. I personally think the above clearance .0012-.0016 recommended is a disaster waiting to happen. I wouldn't change them really much at all. I usually do what you did above, about .0005 smaller. If I would normally want .003, I would run .0025.k-star wrote: ↑Mon Sep 24, 2018 9:27 am Years ago when I was building my first LS aluminum block engine ( Remember those blocks have steel caps not aluminum caps) I was searching the internet for another issue and came across a few discussions on the aluminum block main bearing clearance. The general idea on those threads is that they needed to lose about .0010 clearance cold to make up for expansion. I tried to calculate the coefficient of thermal expansion for the block and the crank, but that got into some calculus formulas that I didn’t understand. So I did an experiment where I measured the Main bores in the block at room temp and then again after I heated them to about 150. (Note: I know that the mains run closer to 230 for temp but could not get the block that hot). I then heated the crank in my jet washer to 180 and measured that. What I came up with both grew about the same amount. The block maybe a few tenths more. So when I built that engine I made the mains about .0005 smaller then what I would usually run them. Kind of a red neck way of doing things, but I never had any issues with that engine.
That is what I am looking at. Thanks They don't grow as much as one would think.Frankshaft wrote: ↑Mon Sep 24, 2018 9:32 amThat's actually a good way to do it. How else could you? I have done the same thing. Its amazing how much a rod for example grows on the housing bore from 2 minutes in the jet wash. I personally think the above clearance .0012-.0016 recommended is a disaster waiting to happen. I wouldn't change them really much at all. I usually do what you did above, about .0005 smaller. If I would normally want .003, I would run .0025.k-star wrote: ↑Mon Sep 24, 2018 9:27 am Years ago when I was building my first LS aluminum block engine ( Remember those blocks have steel caps not aluminum caps) I was searching the internet for another issue and came across a few discussions on the aluminum block main bearing clearance. The general idea on those threads is that they needed to lose about .0010 clearance cold to make up for expansion. I tried to calculate the coefficient of thermal expansion for the block and the crank, but that got into some calculus formulas that I didn’t understand. So I did an experiment where I measured the Main bores in the block at room temp and then again after I heated them to about 150. (Note: I know that the mains run closer to 230 for temp but could not get the block that hot). I then heated the crank in my jet washer to 180 and measured that. What I came up with both grew about the same amount. The block maybe a few tenths more. So when I built that engine I made the mains about .0005 smaller then what I would usually run them. Kind of a red neck way of doing things, but I never had any issues with that engine.
What I was thinking Frank and Nate!needforspeed66gt wrote: ↑Tue Sep 25, 2018 4:16 pm I setup all the LS aluminum engines with .0017"-.002" max main bearing clearance on a 2.559" journal...many are supercharged racing applications with over 1K HP and on tear down the bearings look like new, great oil pressure with 30 weight, 40 if they're really getting the oil temps up.
That too thanks Bill!engineguyBill wrote: ↑Tue Sep 25, 2018 12:28 pm Adam,
Main bearing clearance in an aluminum block is not critical, use the same clearances that you would use with a cast iron block. What is important though is the housing bore dimension. Aim for the minimum bore diameter, or very close to it.
Is that cam bearing loctite deal a FE peculiarity due to the narrow bearings and limited contact area or something you like to do on all engines?blykins wrote: ↑Wed Sep 26, 2018 6:06 am I set all-aluminum FE's up with .002" main bearing clearance. No issues there.
Also remember that the blocks grow considerably, which will affect your compression ratio, valve lash, etc. Also remember that you need to do something about the cam bearings....pin them, green Loctite them, etc.
Dave, I don't particularly like aluminum blocks and don't do many of them anymore, but I secure the cam bearings in all aluminum blocks.Dave Koehler wrote: ↑Wed Sep 26, 2018 7:45 amIs that cam bearing loctite deal a FE peculiarity due to the narrow bearings and limited contact area or something you like to do on all engines?blykins wrote: ↑Wed Sep 26, 2018 6:06 am I set all-aluminum FE's up with .002" main bearing clearance. No issues there.
Also remember that the blocks grow considerably, which will affect your compression ratio, valve lash, etc. Also remember that you need to do something about the cam bearings....pin them, green Loctite them, etc.
How to you deal with the loctite if you need to freshen the cam bearings?
Please allow me to correct you.k-star wrote: ↑Mon Sep 24, 2018 9:27 am Years ago when I was building my first LS aluminum block engine ( Remember those blocks have steel caps not aluminum caps) I was searching the internet for another issue and came across a few discussions on the aluminum block main bearing clearance. The general idea on those threads is that they needed to lose about .0010 clearance cold to make up for expansion. I tried to calculate the coefficient of thermal expansion for the block and the crank, but that got into some calculus formulas that I didn’t understand. So I did an experiment where I measured the Main bores in the block at room temp and then again after I heated them to about 150. (Note: I know that the mains run closer to 230 for temp but could not get the block that hot). I then heated the crank in my jet washer to 180 and measured that. What I came up with both grew about the same amount. The block maybe a few tenths more. So when I built that engine I made the mains about .0005 smaller then what I would usually run them. Kind of a red neck way of doing things, but I never had any issues with that engine.
