4094 M2 main bearings

[Nacho-RT74]

Dissasembling my engine, found a problem on mains. It seems they would need to be resurfaced. They are standard but don't want to cut them 0.010" if is not necesary. HOWEVER found somebody is selling these Mains bearings with PN 4094 M2 on box and seller told me they got stamped the L002 numbers. Seller claims that means is 0.002" undersize. Is that true ? I could get my mains "resurfaced" to that size and will save from cut to 0.010"

 

[Nacho-RT74]

Mechanic told me it could be polished and install fresh standard bearings again without problem. It looks uglier that really is. Barelly can be feel some irregularity. But preffer to resurface them at .002 since found available these bearings.

Of course if the PN and stamped numbers really confirm these are .002 undersize

 

[lewtot184]

never heard of a .002" under main. there used to be .001" under rod bearings.

 

[Nacho-RT74]

Actually Mopar parts catalog show .001, .002, .003, .010 and .012 LOL

 

[Hemirunner]

You can't polish off .002 worth of material easily. Polish it up and mic it. You could probably use standard bearings and be fine. You'll be lucky to have removed .0005".

 

[Nacho-RT74]

Ok. Will work on that. Still need to take it to machine shop and confirm. I already have new standard bearings in hands, but will buy the .002 ones just in case need to be cut.

 

[bm02tj]

Do not buy as it will be cheaper to grind .010 than try to polish the 0.002 accurately
see your machine shop first
Loose is better than tight

 

[Fran Blacker]

Engines with a maltese cross came with undersized bearings. Got a Hemi crank with number 5 main and 5-6 and 7-8 rod journal .001u/s.
Anybody have a .001 u/s number 5 main for sale.

 

[Hemirunner]

Engines with a maltese cross came with undersized bearings. Got a Hemi crank with number 5 main and 5-6 and 7-8 rod journal .001u/s.
Anybody have a .001 u/s number 5 main for sale.

The rod bearing is a CB527HND1 and is available anywhere. An extra thou on a main wouldn't hurt anything. Same on the rod, but those bearings are available individually. Just buy a standard set and run it. A coated set will close it up by .0006 or so. A good rule of thumb for minimum clearance is .001 for each inch of diameter. A 2.75" main should have .00275" min clearance. .003 or even .0035 wouldn't hurt a thing.

 

[Cranky]

Like mentioned above, polishing it .002 isn't an easy task and no grinders that I know of want to even mess with taking .002 off of any kind of shaft and if the shaft is running out .001", then it's even more difficult and I've seen them run out .003 before. The machine and the machinist have to be one with each other to do that close of work. I used to machine pump shafts from bar stock and we were supposed to leave .010 on it so the grinder could do a precision finish on it and make it true. Our grinder was pretty good and I tested him by leaving less and less. He said .005-.006 with no run out was perfect until I started leaving only .004 on them and that's he he started bitching. He said it took too much time being careful to not kill it lol.

 

[moper]

Polishing doesn't even remove .001. If it were me I'd just have it cut .010. There is virtually no loss in stength doing this, and Mopar cranks are notoriously strong. That dimension is because cutting and polishing it to a smaller dimension is more difficult, and easier to mis-measure in a mass production situation. Cut them .010 and know they're good to go. Because that really looks ugly. Did you measure it or try using plastigage to check it?

 

[dieseldazzle]

I'd just have that crank cut. It's not much more money than polishing and will need only .010 max and then you don't have to play the bearing game.

 

[Cranky]

IF you work at it hard and long enough, you can remove .001 or even .002 with the right grit but no one I know would want to do that.....

 

[miller]

Jumping in, and grinding the journals -.010, easily knocks off a full 100,000 mile run off the crank. At least that's my warped way of looking at it.

Main thing on the journals is...are they straight, and round...even as they look.
I've had them like that, and polished them out. A good machine shop would have the right equipment, to do it right, and even taking a full .0005 off, probably keeps good limits.
But, depends on what they measure now. Let your machine shop look.

 

[moper]

No offense meant, but that is a warped way of understanding...lol
One turns a crank to renew the surface for the oil wedge to form on. It needs a flat, smooth surface for that to form. It's the oil that carries the load. If the whole journal is used for that there's very little wear, ever. If there are high spots or the journal is egged or tapered, the oil can't do it's job as well, causing problems locally on the journal and overall in the engine. The reason the cut goes +.010 is it's easy to machine and maintain, and very few scratches or defects will go further than .005". Mopar cranks are way over-built. They can be turned down quite a bit with no real loss of strength (beyond going through the surface hardening if it goes smaller than .020"). How do you think the 440 cranks are fit into a 400 block? They cut them .125" smaller to fit the block...

 

[miller]

None taken, moper.

Sure, I completely understand what your saying, and many do exactly what your saying. Makes it easy, don't it.
Probably too old school (and like it!), though I've spent most of my adult life working on engine parts...mostly crankshafts. So, have a bit of thoughts on crank journals. Know how they should be, and how they work.
Nothing against your thoughts. Just don't believe it's needed to take off .010, when .002 will do it.
But, I'll admit, alot of the stuff I've worked on, there were no shiny new ones that could be store bought. So, you deal with what you have, and make use of it.

 

[Nacho-RT74]

I can try to get them to 002 and if not, allways get a chance to get to 010, but never backwards.

The deal is locally I just have the chance to find 010 but these 002 are in the States at a very good price. A friend of mine is in the States and will be coming to Venezuela next week.

I think worths the try

This is a stock 440 crank grounded to 400 in fact.

A mechanic told a polish an fresh standard bearings will hold but I preffer IF 002 cut is posible the get a new ground job on them. The pictured main journal is the worst of all 5 and is the number 3.

 

[Cranky]

If the throws are in good enough shape, you can polish them and just grind the mains. I know guys that have just did one or two mains or throws before but then you have to buy two sets of bearings but if you work with this stuff long enough, you end up with extra bearings. Over the years I've had several people give me broken sets. I've never done that myself but still have odd bearings. Ya just never know when you might mess one up and having some extras laying around never hurt anything.

 

[miller]

Appears to be a steel (forged) crank. Overall it looks like normal wear on it, that bearing is another story.

A 'complete' measuring on the crank will tell the story, if it needs to be ground, or just a good polish. The journals must be round, and straight, and be that after any work.

 

[Nacho-RT74]

Yes, is forged

This engine has being riding around just 2 years but as daily driver. Even interstate highways once a week for sometime

I guess this happened once I was riding around and sudenlly heard a tapped sound and the oil pressur went down. For safety reasons ( Venezuela us a dangerous country ) I didn't want to stop and wait for a tow. Was close to home and arrived home in 3-5 minutes without revving up the engine.

At next day removed valve cover and found a pushrod bent and a lifter out of the bore. That was the oil pressure fall. But never thought could affect the crank like that. This was long time ago. But after that the car still was riding around a year and a half more.

My car it at body shop now and wanted to check the engine at the same time. I found a badly decked engine, and working now on get quench. All this time I have got pinging arriving to 3500-3700 RPMs without load or at 2400 RPMs or so if loaded ( or going up a hill )