Now I know.
Polishing... you mean with some emery cloth? Seen it done (even did it in 1977 in machine shop...), but how do you do that on a crank?
I have an after-market drain plug that is magnetized.

 

It would have NEVER occured to me that there could be a spread like that. Almost seems intentional, as both 1 and 5 are the same. So what do I do, just mix sets? Order individual bearings?

 

Thank you! Never would have thought to check breaking resistance vs what it takes to keep it spinning. Lot's of other good reads there, thanks.

 

Just add “X” bearings on 2,3,4 mains…..you have to buy the whole set….
Don’t leave it like that….too tight.
You will find that even with the center three at .0015 that the crank will still spin freely….opening the clearance has zip to do with how hard it is to spin unless the bearings are metal to metal or close to it…..
I keep X bearings on the shelf…..it is standard engine builder parts stock to have one over and one under bearings….or your build is stopped in that moment you find out…..
At .0015 your oil pressure will be high….all over….I want .003 on mains and .0025 on rods….but .0025 will do….

Jebby

 

@Jebbysan I’m sorry, you lost me… “X”?

 

They are .001 undersized from the advertised number. Some bearing manufacturers will have bearings that are only marked .010, .030, .040. .060 over bore but sometimes its too much so they have .010X or .030X which is .009 or .029 so you can get more oil clearance. A few manufactures will list bearings as .009, .019 etc but not too many

 

Normally the crank is removed and placed on a machine with emery type belts that can micro fine polish the crank journals and the rod journals if needed.
Only the bigger machine shops would have that type of equipment.

Just my opinion, but I would bet that almost every journal in that engine will "open-up" one one thousandths of an inch after a considerable break-in period.

Bearing sets are fairly cheap, but if you have to buy multiple sets to satisfy each and every journal, then it becomes expensive and laborious.

Are you concerned about the rod bearings also?

 

It may be expensive and laborious.....but that is how it is done......and you do not have to buy multiple sets......in this case...the OP will buy one X set and use the center three bearings......my King -1 and X bearings are less than $40 a set.....
And there is no movement in a properly installed bearing insert once it is installed and torqued. The crank never touches the surface of the bearing.....unless it runs dry, or clearance is way too tight.......if you watch the bearing as you torque the caps down....the ends stick up just a hair and when torqued these crush together and create a "spring" lock, along with the tang....to prevent movement. Once torqued, the bearing will measure after 100,000 miles what it did when new if well taken care of.....

I have run a crank polisher....to get .0005 you can polish it but to get .001 you will be there all day......and rods you have 8 to do as opposed to 5 mains.....

When you walk into any of the engine build rooms that I have...like at Dart, Diamond/Trend, World, our old shop...etc.....there will be a whole shelf of boxes with different inserts in them......X, -1, STD., .010, .011......
Eagle crank are almost always fat and need an X bearing on the main......so you have to keep X on hand if you want to build that day......

Anyway.......what bearing is in it now....? What brand?

Jebby

 

I'm not a giant Plastiguage fan.

I'd love to see you get even a cheap micrometer and dial bore gauge to ensure clearances are correct. It's a new skill you can learn, but it takes a little practice also.

Or take it all apart and haul it to machine shop with bearings in block and torqued with crank out so they can quickly measure it for you. Same with rods...torque the rod caps back in place with bearings in there and they can quickly measure also.

From there you can determine what bearings will get you where they need to be. Or if the line hone is suspect? But from what you've shown, I'm guessing bearing juggling will get you there.

Polishing .0005" off a crank evenly takes a skilled hand...and "machining" that amount is even tougher and requires top of the line equipment.

I had to use "X" bearings throughout my recent blown 408" Clevor build with a new crank and rods. And even then, I'd have liked it a little looser on the mains, but it was OK.

JIM

 

Unpopular opinion, but for a street engine I think your clearances are fine

assemble it and have fun!
I’d be more concerned about checking and adjusting ring gap

 

.0015 is awful tight on a 2.45" main. That's only .00075 between the bearing and a spinning crank. And if that crank has anything except .0000 runout things will get cozy.

And since the goal is to make it have more power and it has more cubes......you have to assume it's going to get hammered once in a while.

This is the time to make it right and sleep good at night.


Thanks,

JIM

 

100%

Jebby

 

I’ll confess that I don’t remember. But it measures.091 and here’s the stamp. Says M557L then HC2 STD.

 

Followup question: Could the measurement be tight because there's oil between the crank and the bearing underneath? When using plastigauge, wouldn't one normally measure completely dry? Or does that not make enough of a difference? If I'm going to replace these then I'm going to have to remove the crank anyway, so I suppose it's moot. I'll end up measuring again, dry, once I've removed the crank. Just more of a curiosity for the sake of the next guy that goes through this....

 

Put oil on the bottom bearing to resist scuffing....the cap should be dry as a recovering alcoholic.....

Jebby

 

@Jebbysan I didn’t mean oil “outside” the bearing, I meant oil between the bottom bearing and the bottom of the crank. Does that small bit of oil affect the measurement I made with plasigauge?

 

Just a skim with your finger....dont soak the bearing....just wet enough so it isnt metal on metal....

Jebby

 

OK, so I went and bought some calipers. Couldn’t find a dial bore gauge so I used a telescoping gauge for the bore. I figure that at worst I’m off .0005”. At any rate,
measured the crank mains and the ends are 2.440 and the three in the middle are 2.4415.
I torqued all caps to 70 and the end caps are about .0015 and the three middle are from .0005 to .001 clearance.

So then since those bearings say STD, then I should get -.001 for the ends and -.002 for the three middle?

 

Shunyun, this is how I was taught to plastic gauge any con-rod or main bearing in Power Mechanics class 101. (Never mind what year that was)

Even Plastic Gauge web site says the same as me.
Install a piece of gauge on a clean dry journal and clean dry bearing.

And I would like to add:
A film of oil, a film of Moly or whatever lube you don't need at this time will throw the reading off by the thickness of the lube. If you have one and a half thousandths thickness of lube, it will give a false reading the bearing is too tight.

However, when all is said and done with that journal measurement, THEN you must apply a moly or whatever before torquing to specs and rotating.

 

You are duplicating the results….but the numbers are way off…..Plastigage is more accurate than snap gauge and calipers…..
You need a 2-3” mic and a dial bore gauge….
There is no 2x bearing…..
You need 1x for the three center as I stated before….
Platigage is more accurate than one would think….but not as accurate as the mic/bore gauge….
Just order both from Amazon….Summit has them too….I have the cheap Summit handle with a mid range gauge on it….it repeats very well….scary almost….and I checked it against my friends Sunnen….it was spot on….

Jebby