1G Main Bearing Clearances?

[craracer05]

So went and did some measureing on my block tonight to try and figure out if I can get this car back on the road.

i measued all the main caps at 61mm all the cranks mains at 56.74mm and my clevite 77 bearings at 2.28mm thick.

from what I figured that makes me .0059" of an inch too tight??????

 

[craracer05]

I had the crank machined .010" so I ordered .010" oversize bearings as well.

 

[Jeff99GS]

The stock reccomended clearances are .0008 through .002

Try to use some plastigage and see how that reads.

I have heard of people using as large of a gap as .006 in racing applications. But I have No first hand experience with that.
My engine was .002 on all Mains and rods.

 

[My1GLaser]

The proper way to measure them is by putting the bearings in the block/cap and torque the caps to spec. Then measure with a telescoping bore gauge or something similar and subtract the crank journal diameter.

I plastigauged mine and that was sufficient for me. They were between .002 & .0025.

And .0059 would be way too loose. .003 is about the max I would feel comfortable running and then you would need to run heavier weight oil to ensure you had good pressure.

 

[Big Woo]

Did you measure these with the main caps, bearings installed and torqued? If not your numbers as mentioned are off. This is because the torqueing process stretches bolts/studs firmly beds main caps into thier respective block registers, and apples a known amount of crush to the bearings.

If a dial bore is not available for measuring the bearing clearances with the bearings and main caps installed and torqued, without the crankshaft, then I would also reccomend the plasti-gauge method.

 

[craracer05]

Ya i"m just going to get a plasti gauge and see whats up, I returned my dial bore gauge last year when I ditched the project. But does anyone know the listed size for the block main bearing bores?

 

[craracer05]

Well through it together today plasti-gauged it and cam up with .04 to .05mm on all the mains. Which accordding to my service manual is right on spec towards the loose end.

 

[craracer05]

Can anyone chime in and let me know if they think I'm good to go or not?

 

[Jeff99GS]

I think that clearance is TOO big. But you can try it I guess?

Run some thick ass oil.

 

[My1GLaser]

That comes out to .00157-.00197." The service manual calls for .0008-.002" with a service limit of .004". So as you said, you are on the loose side of the OEM spec.

3 of mine were .002, with one at .0017 & .0025. I have no balance shafts and run 10w40 Castrol to make sure I have sufficient oil pressure. I have 6,000 miles on the build.

I think you will be fine, as long as you measured them correctly.

 

[donniekak]

That comes out to .00157-.00197." The service manual calls for .0008-.002" with a service limit of .004". So as you said, you are on the loose side of the OEM spec.

3 of mine were .002, with one at .0017 & .0025. I have no balance shafts and run 10w40 Castrol to make sure I have sufficient oil pressure. I have 6,000 miles on the build.

I think you will be fine, as long as you measured them correctly.

I dare anyone to mod their car while running the .0008" listed in the manual. That is a joke. On a car with any real power i usually go at least .0025". I also delete the balance shafts. These cars have a great oiling system, at least the 6-bolts. This allows the use of a proper high performance oil clearance. You should see what the nhra guys run.