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As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.:no:

Tim
 

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As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.:no:

Tim
I actually think you answered your own question! Jocko
 

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As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.:no:

Tim
I don't remember anybody saying those numbers are too big. Maybe bigger than necessary, but they will work fine with the right oil.
You don't mention what the "too tight" clearances were. Maybe they were, maybe they weren't. The clearance you can "get away with" has a lot to do with the quality of the crankshaft and block machining.
A less than dead nuts straight crank and dead straight align bore require sloppier clearances.,



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Discussion Starter #4
The tight clearance was the .0025/.0030. Thats what I had when I built the engine in'03. '08 I took it down for inspection and found #3 rod bearing down to the copper. The crank was turned .010/.010. After that is when I had the bearing problems and later found out the crank was bent from turning the mains. The mains have been honed before I built the engine in '03. They were confurmed straight by a different machine shop when I was having the problems. Now it seems that the .0025/.003 is the recommended clearance. Just curious that there seems to be a change on what is recommended.

Tim
 

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.003 mains, .0025 rods is a very generic, safe, "performance" bearing clearance. It's not even close to tight.
Clearances are dictated by a number of factors; oil type and weight, oil temp, HP and rpm, and the quality of parts as well as the intended usage.
FYI... .0002" of added bearing clearance on a SB Chev can mean as much as 6 gpm more oil consumption, (more on a BB Chev) and that's just more oil flying around inside your engine and not where it should be.
 

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.003 mains, .0025 rods is a very generic, safe, "performance" bearing clearance. It's not even close to tight.
Clearances are dictated by a number of factors; oil type and weight, oil temp, HP and rpm, and the quality of parts as well as the intended usage.
FYI... .0002" of added bearing clearance on a SB Chev can mean as much as 6 gpm more oil consumption, (more on a BB Chev) and that's just more oil flying around inside your engine and not where it should be.
But it will require him to buy another set of bearings .001 smaller and use the half shells to reduce what he has .0005.
But then, he will have a set of bearings for the next freshen up:happy:



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But it will require him to buy another set of bearings .001 smaller and use the half shells to reduce what he has .0005.
But then, he will have a set of bearings for the next freshen up:happy:
Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable. :)eh:) :D
 

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But it will require him to buy another set of bearings .001 smaller and use the half shells to reduce what he has .0005.
But then, he will have a set of bearings for the next freshen up:happy:
I have a few half-sets of one unders...oh well. No one ever said this was easy or cheap (to do it right)...
 

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Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable. :)eh:) :D
I'd like to see the data to support that.
 

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Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable. :)eh:) :D
I was told the same. Don't know if I buy it. But it sure does make me concerned about using the left over bearings from a the x set for the next rebuild. :)sphss
 

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Ill take all of those leftover sets. Wouldn't want you to put some in and worry about it the whole time. :hmmm:
 

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Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable. :)eh:) :D
I'd like to see the data to support that.
I was told the same. Don't know if I buy it. But it sure does make me concerned about using the left over bearings from a the x set for the next rebuild. :)sphss
Its in one of their tech bulletins. Some BS about loads blah blah blah. The mains were one way and the rods were another. The idea in the rods is a complete joke due to the delta wall. In either case, its a .00025 difference in thickness at each butting. I never had problem doing it either way and stopped worrying about that years, I think it was means to sell more bearings.

Also, according to Clevite, .001 X journal diameter or .0021. But then +.0005 "as a margin of safety" for a starting point. WTF does that mean. A starting point heading to where. They never say. Starting point if this is your first engine? Who flock knows.


Any how, before I would use a half set, I would send the POS out to be coated. My favorite way to rid a little clearance. :happy:
If this thing is blown, I would still use them as is, and still have them coated. But that's me. Your mileage may very.

Page 6 installation and fitting tips

http://www.stealth316.com/misc/clevite-77-rod-main-bearings.pdf



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Yeras ago a Clevite Tech told me you can mix main bearings sets but the thicker half has to go in the cap. I guess that means the set left over is undesireable. :)eh:) :D
Small blocks used to come like that from GM, something about a semi-line bore.

I saw a guy hone a little extra on the big end to get a little more clearance,probably not the right way but it hasn't caused any problems so far.

If i remember correctly GM calls .001 minimum on rods....fine for a basic mo ho but in a boat it will start pitching parts after a few min. @ 5500. 2.199 crank and std brngs and the dummy who assembled it didn't double check machine shop.:hmmm:
 

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Small blocks used to come like that from GM, something about a semi-line bore.

I saw a guy hone a little extra on the big end to get a little more clearance,probably not the right way but it hasn't caused any problems so far.

If i remember correctly GM calls .001 minimum on rods....fine for a basic mo ho but in a boat it will start pitching parts after a few min. @ 5500. 2.199 crank and std brngs and the dummy who assembled it didn't double check machine shop.:hmmm:
The line hone establishes the bearing "crush", not a good idea to jack with that.
 

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Small blocks used to come like that from GM, something about a semi-line bore.

I saw a guy hone a little extra on the big end to get a little more clearance,probably not the right way but it hasn't caused any problems so far.

If i remember correctly GM calls .001 minimum on rods....fine for a basic mo ho but in a boat it will start pitching parts after a few min. @ 5500. 2.199 crank and std brngs and the dummy who assembled it didn't double check machine shop.:hmmm:
I can't say I ever saw GM do that with a SBC, but of the 2 BBCs I have stripped down that I KNOW were factory original, both hand mismatched bearings to account for misalignment. I have built a few SBC that were not align honed, and never built a BBC that wasn't.
Honing bearings for clearance is nothing new. Vic Edelbrock use to use under sized main bearing and align hone the block with bearings installed pretty regularly. But the bearings had .015-..020 of silicon aluminum bearing material. You can hone a King bi metal bearing with no problem.



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Discussion Starter #17
The engine is a N/A 468 single Dom. Has a Callies Compstar crank, Eagle H beam rods internally balanced and the mains have been align honed when converted to 4 bolt. The second machine shop I had it to, said it was done right. I'm running this in a 9 second hydro turning 7500. Sounds like you guys are leaning to the tighter clearance. What brand of bearing is suggested? Plain or coated? Thanks

Tim
 

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As to not to high jack a thread, back in '09 I was having bearing issues. I was running .0025/.003 clearance turning 7500 RPM with an Eagle crank. I found that the crank was bent and replaced it with a Compstar. I was also told my clearances were to tight and I was told to use .003/.0035. They ended up at .0029/.0034. Now lately I've been reading and it seems my clearances are big and it's being recommended to use the tighter ones again. I've checked my bearings and feel I can reuse them and only replace the rings. Now I'm wondering about clearances again.:no:

Tim
I don't get it.
You had "bearing problems".
You changed the crank and the clearance.
Now you have checked your bearings and they look so good you can reuse them.......but you want to jack with that.

Sounds like you need to stop reading so much.
 
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Discussion Starter #19
I don't get it.
You had "bearing problems".
You changed the crank and the clearance.
Now you have checked your bearings and they look so good you can reuse them.......but you want to jack with that.

Sounds like you need to stop reading so much.
:))THumbsUp:thumb: Thats just what I was thinking. Seeing these clearances tighter got me thinking more than I needed. I guess I should have listened to Jockorace in the first place. Thanks



Tim
 

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I don't get it.
You had "bearing problems".
You changed the crank and the clearance.
Now you have checked your bearings and they look so good you can reuse them.......but you want to jack with that.

Sounds like you need to stop reading so much.
x2 ! :thumb: Jocko
 
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