I spent a little time this evening measuring the bearing clearance.

BBC stock GM steel crank, std/std, Eagle H-beam rod, Clevite H series bearing.

mains checked out at(in order of 1 through 5) .0026", .0028", .0030", .0030", and .0038-.0040" for #5.

The rods checks out at .028" to .032".

I assume it's normal for the rear main to have additional clearance as the journal size is smaller than the front four.

Looks like all the journals are on the small size of the spec which is also a factor in the larger clearances.

Give me your opinions if any of these clearances need adjusting.

My initial thought is to leave the mains alone and maybe get a set of 1x rod bearings and use one half of each to tighten the clearance .0005".

Any thoughts?

I want to go through the measuring process again so I can feel comfortable my measurements are fairly accurate.

Just as a note...
main journals
1 - 2.7485"
2 - 2.7485
3 - 2.7484
4 - 2.7484
5 - 2.7476-2.7480 (seems to have taper with the front of the journal smaller and the rear of the journal is larger)

rod journals
1/2 - 2.1989 to 2.1991
3/4 - 2.1988
5/6 - 2.1986 to 2.1987
7/8 - 2.1988

Would welcome any thoughts.
thanks
Todd

I would definitely tighten up the rods as you've noted. IMO, I'd do the same for the rear 3 mains. I'd probably go for the whole -.001 in the thrust myself. I'm sort of death on sloppy clearances, myself. don't see the point of it, just spewing oil all over the place.

Todd,

I'm certainly no expert, but I used .0025-.0028 for rods and mains on my engine based upon my machinists advice. Engine has good oil pressure 25-30lbs warm idle and 80lbs WOT.

Todd,
Did you check the rear main with the oil pump bolted on?
Don't forget to check the thrust clearance.
You can tighten the rods up .0005.

No, I quite for the night before pulling the oil pump out and torquing it in place. I'm sure that rear main clearance will open up even more once the oil pump is on. Thrust will be checked once the bearing clearances are set and the crank is ready to be installed for the last time.

thanks for the replies thus far folks
Todd

Gotta give the machine shop a call and see if he stocks the .001" bearings of if they need ordering.

Todd, FWIW
My mains came in at:
.0025
.0025
.0027
.0025
.0035
Thrust = .0055
Crank runout was max .0001 at #3 main

I think the minumum spec for 1-4 mains is 2.7485".
You had a couple a hair smaller than that.

todd, another way you can measure your clearance is to measure the housing bore without the bearings installed then check to see how thick the bearing is using your mike add these to together then subtract the crankshaft journal measurement and this will be you clearance. its always a good idea to check the housing bore first just to see if some bores are lower than others. this can also affect bearing clearance. i dont know if you had the block alighned honed or not.

nevermind on the above todd. i mest up. sorry

I spent a little time this evening measuring the bearing clearance.

BBC stock GM steel crank, std/std, Eagle H-beam rod, Clevite H series bearing.

mains checked out at(in order of 1 through 5) .0026", .0028", .0030", .0030", and .0038-.0040" for #5.

The rods checks out at .028" to .032".

I assume it's normal for the rear main to have additional clearance as the journal size is smaller than the front four.

Looks like all the journals are on the small size of the spec which is also a factor in the larger clearances.

Give me your opinions if any of these clearances need adjusting.

My initial thought is to leave the mains alone and maybe get a set of 1x rod bearings and use one half of each to tighten the clearance .0005".

Any thoughts?

I want to go through the measuring process again so I can feel comfortable my measurements are fairly accurate.

Just as a note...
main journals
1 - 2.7485"
2 - 2.7485
3 - 2.7484
4 - 2.7484
5 - 2.7476-2.7480 (seems to have taper with the front of the journal smaller and the rear of the journal is larger)

rod journals
1/2 - 2.1989 to 2.1991
3/4 - 2.1988
5/6 - 2.1986 to 2.1987
7/8 - 2.1988

Would welcome any thoughts.
thanks
Todd
=
Hi Todd,
Thanks for the email, sorry for not replying, haven't been on as much. Busy as hell right now.
I think Tom & Ken answered it pretty good & you definitely want the pump on when checkin the rear.
I have a cut off pump that I use when measuring or line honing the block.

First, 1X will make it looser, you want .001 under.
I would put a half shell in #3 & 4 main & an .001 in # 5
Rods I'd leave the .0028's & put a half in the rest although in reality anything under .003 is fine.
I would probably just put a full set of .001's in the rods & see where you are.
I also prefer clearances on the tighter side.
Try to adjust everything to a nominal .0025 but don't get crazy
chasin tenths :D
If you can get .0022-.0028 great. If you have the rear at .003-.0032 or so I'd live with it.