I would like to hear what options there are, for increasing bearing clearances.
 In particularly, clearances on a turned down crank!
 After going thru a long block that i recently picked up and just checking the main and rod clearances with some plastigauge, looks like the they are a little tight.
 The crank is a 10/20, freshly ground, with new bearings. I verified that the bearings are Clevite P series ,010 and .020 undersize bearings.
 With pastigauge, the mains came in at, #1 .002, #2 .002+/-, #3 .002, #4 .002+/-. I say #2 & #4, +/-, because it didnt appear to be dead nuts on the 2 thousandth gauge width.
 Rods 1-8 appeared to be .0015, as best as i could tell.
 I have #1 piston out, so for curiosity, i miced the #1 rod journal and it measured 2.1790. If a standard rod journal is 2.1990, that 1.020 under size, right?
I zeroed a bore gauge to the mic and compared the rod bore, with bearing, torqued to spec, measured 90* from parting line, and found a
 .0015 differance. Kinda backs up the plastigauge, if i did it right?
 This is not a big Hp motor, but it is pretty much an Ls6 454, with i think a smaller cam profile.
 I need to get the clearances figured out, so i can get on with putting this back together.
 
So what are the options for increasing cleasances, in a situation like this?
 H

Hal, you should be able to get the clearance you want by simply purchasing a set of bearings that are -.001 from what you have. In other words, buy a set of .009" main bearings and .019" rod bearings. If that leaves you with too much clearance, then use 1 .009" and 1 .010 per journal for mains and make the same split with the rods, if they need it.

I would like to hear what options there are, for increasing bearing clearances.
 In particularly, clearances on a turned down crank!
 After going thru a long block that i recently picked up and just checking the main and rod clearances with some plastigauge, looks like the they are a little tight.

I hate plasigage. With a passion. It is too temperamental and prone to mistakes. Just want to get that out of the way.


 

The crank is a 10/20, freshly ground, with new bearings. I verified that the bearings are Clevite P series ,010 and .020 undersize bearings.
 With pastigauge, the mains came in at, #1 .002, #2 .002+/-, #3 .002, #4 .002+/-. I say #2 & #4, +/-, because it didnt appear to be dead nuts on the 2 thousandth gauge width.

Like I mentioned before, the stuff is really not that accurate, especially if the temperatures were over 80*F (gets really soft and smears).


 

Rods 1-8 appeared to be .0015, as best as i could tell.
 I have #1 piston out, so for curiosity, i miced the #1 rod journal and it measured 2.1790. If a standard rod journal is 2.1990, that 1.020 under size, right?

No, .020". (Certain of a typo)
 

I zeroed a bore gauge to the mic and compared the rod bore, with bearing, torqued to spec, measured 90* from parting line, and found a
 .0015 differance. Kinda backs up the plastigauge, if i did it right?

You should measure the rod in three places, but yes. How clean and were they totally dry? I use carburetor cleaner and lint free shop towels during this process.

Something to consider. The bearing itself may not be the issue. The rod big end could be distorted and or not providing the amount of crush necessary, Have you checked numerous bearings on the same rod? Sometimes this is all it takes to bring them in.




 

This is not a big Hp motor, but it is pretty much an Ls6 454, with i think a smaller cam profile.
 I need to get the clearances figured out, so i can get on with putting this back together.

Spend the time to mane sure it's right before rushing and throwing it together...
 

So what are the options for increasing cleasances, in a situation like this?
 H

With some Scotch Brite and some time, you can take and rub the silver exterior surface of the bearing to get your .0005" you need. Were the rods resized properly?

Once you have the fit you are looking for, be sure to mark the bearings and rods with a Sharpie for identification.

Good luck, and good on you for checking.

GT

I hate plasigage. With a passion. It is too temperamental and prone to mistakes. Just want to get that out of the way.


 
Like I mentioned before, the stuff is really not that accurate, especially if the temperatures were over 80*F (gets really soft and smears).


 
No, .020". (Certain of a typo)
 
You should measure the rod in three places, but yes. How clean and were they totally dry? I use carburetor cleaner and lint free shop towels during this process.

Something to consider. The bearing itself may not be the issue. The rod big end could be distorted and or not providing the amount of crush necessary, Have you checked numerous bearings on the same rod? Sometimes this is all it takes to bring them in.




 
Spend the time to mane sure it's right before rushing and throwing it together...
 
With some Scotch Brite and some time, you can take and rub the silver exterior surface of the bearing to get your .0005" you need. Were the rods resized properly?

Once you have the fit you are looking for, be sure to mark the bearings and rods with a Sharpie for identification.

Good luck, and good on you for checking.

GT

Glenn, I was using the plastigauge to to get an idea, as to where things are at, due to the long block allready being  assmbled. The guy that assembled it, said that  the clearance was at around .0015.

Yes, .020. The 1 is a typo!

Yes totaly clean and dry, but im not a pro at this.
I was just trying to verrify the plastigauge on the one rod, to see if maybe i was way off. It is the only piston that i have out.

All the rods were resized. Resized right, i dont know? They were done by a machine shop,here in town.

Not a genius here, but you are only talking a difficult to confirm half a thousandth, I would say they are all a little "tight" for my taste, would you not want .021" bearings? Thinking you are looking at it backwards.

How are the mains?

On most jet pump applications for a big block, I like to see .0025" to .0030" final clearances. But I also run 40 or 50 wt synthetic racing oils.

GT

I dont know, maybe i am backwards?
The rod Journal is turned .020" undersize(smaller than standard) it has a .020" undersize bearing. The clearance measures .0015". To get to .0025"min, i need another .001". A .019" bearing, is larger( diamiter) than a a .020" bearing, by .001", right?
So to gain a full thou, i would need a .019"?

The mains are at .002, They are cut to .010 undersize. If I wanted to increase clearance, by .0005", then i would need a half shell of a .009 undersize? If i wanted to gain a full thou, to get to .0030, then I would need a full .009 under size bearing? .009" is larger( diamiter, than .020, when talking undersize, right?
 Or is my brain thinking backwards? Its been known to do that sometimes!

I dont know, maybe i am backwards?

You're not... I spent too much time in the sun this morning... 

The rod Journal is turned .020" undersize(smaller than standard) it has a .020" undersize bearing. The clearance measures .0015". To get to .0025"min, i need another .001". A .019" bearing, is larger( diamiter) than a a .020" bearing, by .001", right?
So to gain a full thou, i would need a .019"?

You know what, My bad, I had finished dimension in my head, you are correct, you would order .001 less under bearings. My bad. Going 100 MPH getting ready to head up north and wanted to give you another opinion.

Sorry about that.

The mains are at .002, They are cut to .010 undersize. If I wanted to increase clearance, by .0005", then i would need a half shell of a .009 undersize? If i wanted to gain a full thou, to get to .0030, then I would need a full .009 under size bearing? .009" is larger( diamiter, than .020, when talking undersize, right?

Yes, you would need to change the lower half to a .009".

Or is my brain thinking backwards? Its been known to do that sometimes!

Nope, this ones on me brah.

GT

What engine did you end up with?

Its just a 454 BBc.
For all intense and purposes, it is an Ls6 454, with the exception of the open chamber heads, instead of closed.
454 stnd 4 bolt block
990 rectport open chamber heads
4.00' steel gm crank
6.135" steel gm  "dimple rods"
forged trw dome pistons (Ls6 spec)
The cam has been swaped out to a wimpy comp cams, http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=387&sb=2 but it should be ok to just get back on the water, for now.

Basically... the only way you're gonna do this right is to have it measured with a quality set of mics and a quality bore gauge... if you do not own these... seek out someone that does, a decent machine shop should. Second... once you determine your actual current clearance and decide that they need to be opened up... then size the rods and main bores accordingly... as long as the resulting resizing does not exceed the tolerable limits of housing size... otherwise your bearing crush will not be ideal. Theroetically, if the crank journals are within a nominal undersize... and you are using a quality bearing, such as a Clevite (not china junk), then sizing the main and rod bores to achieve the desired clearance will typically land you on the high side of the spec.

X2
Do it right the first time - I've tried a lot of things like some have suggested and as well as matching bearings to different journals, easier to just have the machinist do it right so that bearing crush is correct and the same for all journals. (mains & rods)

JW