Tight(ish) main bearing

Throwing together a ford 2.3 turbo.

1st 2nd 4th 5th bearings measure between 0.0020 - 0.0026

3rd middle thrust bearing coming in at 0.0015 

I can source a +0.001 thrust bearing to gimme 0.0025

No budget left for anymore machine shop work. All the crappy used components I bought needed repaired so funds are limited.

Should work, eh? 

Soak some emery paper in carb cleaner or kerosene or something and then rub it against itself to "kill" it, then clean some of the overlay off of the bearings?

Old Mazda Rotary method of making high clearance race bearings out of stockers.  The overlay in the stock bearings in those was about .0005" thick so sanding it completely down to the copper would add .001" clearance.  Overlay is only there to embed garbage, some people would rather have the garbage floating in the oil than have it embed and continue graunching away at the crankshaft... 

Knurled said:

Soak some emery paper in carb cleaner or kerosene or something and then rub it against itself to "kill" it, then clean some of the overlay off of the bearings?

 

Old Mazda Rotary method of making high clearance race bearings out of stockers.  The overlay in the stock bearings in those was about .0005" thick so sanding it completely down to the copper would add .001" clearance.  Overlay is only there to embed garbage, some people would rather have the garbage floating in the oil than have it embed and continue graunching away at the crankshaft... 

 

 

I rather not modify the bearings if I could avoid it to be honest.

Start it up without oil for a few minutes?

(seriously though, don't do that)

curtis73 said:

Start it up without oil for a few minutes?

(seriously though, don't do that)

At the last LeMons race, the oil pump pickup fell off and the car made a full lap (2 miles) on a 460 Ford turning 2000-3000 RPM with 0 oil pressure.  Fixed the pickup, started the engine up, and it ran great and seemed to have even more power.  We joked that we'd opened up the bearings to "race tolerances".  
We also run Mobil1 15W-50.  So even with 0 pressure, there was probably a good bit of residual lubrication available.  

I would try to "polish" the #3 crank journal to open the clearence up a bit. Take some 1 inch wide emery cloth and treat that journal like an old shoe.

Yes, a +0.001 bearing will do what you're after.  If it turns out that you end up with too much clearance you can run one std and one oversize shell although I don't really like to do that with main bearings.  You can also try another std bearing from another manufacturer.

Chilton says:  .0008 to .0024

Got some +.001 So I'll throw those in. 

I'd leave it and assure myself of better oil pressure at the end of the crank furthest from the oil feed.  Also, I would turn the crank 90 degrees and measure all the bearings again at the same spot.  Could be a slight bend in the crank.

Measuring was done at shop with bearings only installed.

If your machine shop does its own crank work, they can micropolish that journal a little more and get you to .002." Otherwise, I'd leave it alone.

ScotchBrite the bearing shell to open it up.

You need to make sure your crank is not bent.

Rotate the crank 180° and remeasure.

I'm gonna lean hard on this... if it weren't the middle thrust bearing I would leave it too Jerry 

bentwrench said:

ScotchBrite the bearing shell to open it up.

You need to make sure your crank is not bent.

Rotate the crank 180° and remeasure.

I read the faq on the bearing suppliers website and it said under no circumstances should the bearing be modified. A rub with newspaper was all that was permitted! I was gonna email and see what they thought about sanding the rear of the bearing.  Lol

Craigorypeck said:

I'm gonna lean hard on this... if it weren't the middle thrust bearing I would leave it too Jerry 

Please clarify. You keep saying "thrust bearing" - flat pieces that take up end-play in block/ crank relationship. 

Are the suggestions given so far, for that? Or, is everyone misunderstanding you, and talking about journal bearings?

iceracer said:

Chilton says:  .0008 to .0024

So .0015 should be just about as middle of the tolerance, eh? 

Craigorypeck said:

I read the faq on the bearing suppliers website and it said under no circumstances should the bearing be modified. A rub with newspaper was all that was permitted! I was gonna email and see what they thought about sanding the rear of the bearing.  Lol

Don't sand the rear of the bearing. Changing the OD could dramatically increase the risk of spinning the bearing.

RealMiniParker said:

Craigorypeck said:

I'm gonna lean hard on this... if it weren't the middle thrust bearing I would leave it too Jerry 

Please clarify. You keep saying "thrust bearing" - flat pieces that take up end-play in block/ crank relationship. 

Are the suggestions given so far, for that? Or, is everyone misunderstanding you, and talking about journal bearings?

On this particular engine the middle main bearing is also the thrust bearing.. 

gearheadE30 said:

Craigorypeck said:

I read the faq on the bearing suppliers website and it said under no circumstances should the bearing be modified. A rub with newspaper was all that was permitted! I was gonna email and see what they thought about sanding the rear of the bearing.  Lol

Don't sand the rear of the bearing. Changing the OD could dramatically increase the risk of spinning the bearing.

I was kinda joking there

In reply to Craigorypeck :

Gotcha. After posting that, the combined thrust/journal bearing idea came to me.