The Stovebolt Site Forums The Shop Area Engine Shop Main bearing question...

:confused: Okay, something as simple as installed insert bearings in the lower end of my engine shouldn't be complicated correct? I mean I know that I have them facing the proper way and that I am not trying to stuff and end bearing in an intermediate slot and vice versa. However, the bearing that acts as the thrust bearing (what my machine shop told me) does not want to fit the journal on the crankshaft. It fits in place on the block and the cap, but when I go to lay in the crank, all bearings fit the journals except for this one. The thrust bearing is the intermediate located towards the flywheel, correct? Please help, I am getting ready to have my machine shop order another set and eat these. Thanks.

oh yeah, the engine is a 1959 261. Sorry about forgeting the minor details.

Will the bearing shells fit onto the crankshaft when they're out of the block? Sometimes a thrust face must be fitted to the crankshaft by using a piece of plate glass and some fine-grit sandpaper to establish the right end play. Try to fit the bearing onto the crank journal, and check the side clearance with a feeler gauge. Some thrust bearings are supplied intentionally tight, and need to be fitted for correct end play.
Jerry

Jerry,

The thrust bearing is very tight, I did try to slide into the journal but couldn't even get it seated all the way. I don't have a plastigauge available at the moment. I understand the tight fit theory and sanding it to fit, but how tight or oversized is too much? Would it be worth taking the crank and bearing to my machine shop and having them toy with it to get it right? If not, what grit of sand paper would be appropriate for this and what steps do I need to take to get smooth, even sanding on all points of the bearing? Thanks for the input, I do feel a little better about the situation.

A 261 uses the same crank as a 235. I've built several 235s, and never had to sand a thrust bearing. Sanding thrust bearings was a procedure done 40 years ago to fit the parts. The shoulders on the thrust bearing take the fore and aft movement of the crankshaft. Typical values are .003" to .009" thrust clearance on the thrust bearing, taken between shoulder of bearing and crank thrust face. The insert should just slide on. The Clevite or Federal Mougal bearings should fit correctly. A machine shop is needed to insure that the bearing is the correct one, and the crankshaft has been machined correctly.

I once had a 235 engine come apart due to a failed thrust bearing. The crank walked back and forth and beat the hell out of the rods and chewed up the bearings. The thrust face on my store-bought crankshaft was poorly machined, and it ground down the thrust bearing inserts in about 10K miles.

good luck

chip

I agree, the thrust bearing should fit correctly, without hand-fitting, but it depends on who did the crankshaft grinding, and the radius they put on the shaft where the bearing area meets the thrust face. If you look at the edge of the bearing surface, next to the vertical area for the thrust face, there should be a rounded transition, not a square corner. If the radius is too broad, the bearing will not fit onto the flat part of the shaft. It's called "radius ride", and is responsible for a lot of bearing failures on the thrust bearing. In the "crankshaft specifications" part of any good service manual, there's an "end play" spec. That's the amount of front-to-rear movement the crank is supposed to have, and it's controlled by the thrust bearing. If you use a feeler gauge beside the thrust bearing, you can figure end play before the bearing is installed. For instance, a .005" feeler gauge clearance between the thrust flange and the crank will translate to the same amount of end play with the bearing installed. If it's necessary to adjust end play, I use a piece of plate glass, some lightweight oil, or cleaning solvent, and a piece of 400 grit wet-or-dry sandpaper. Lap the bearing thrust face (ONLY, not the round part) in a figure-8 motion until the clearance is correct. if both bearing shells have thrust faces, (most do), make sure clearance is equal on both bearing shells, and that the adjustment is done on the same side. Another method is to have the crank grinder measure the bearing shell, and grind the correct clearance into the crankshaft. Any good crank grinder should do that as part of the regrinding procedure, but some don't bother to fit thrust bearings correctly. Fittng a thrust bearing, using the procedure I've described, is a last-resort method to save a problem job!
Good luck!
Jerry

Thanks guys for all the input. The crankshaft just came back from the machine shop, like the engine. Everything was turned, honed and bored. I even had the head redone. So, you could imagine my surprise. I am going to go back to the machine shop and have them resolve it, hopefully, it won't cost me much extra. What would you expect? Is this something that they should have inspected in the first place? I had them order the bearings for me, should they have checked the fit? And would it be reasonable for me to ask them to resolve this issue without further compensation? Just curious. Thanks again for all the input.

Jerry, I will check the crank for some of those subtle details you were talking about with respect to the journals.

-Shane

Oh yeah, the bearings are Clevites. So, quality shouldn't be an issue here.

Pick up the phone and call the shop. Explain the problem to them. Sounds like they ground the wrong radius on the crank. I would expect that since you bought the parts there they will make it right. Most machine shops treat their customers right.

Just got off the phone with the machine shop and he is going to check with the bearing supplier. He suspects the journal is not to specs as well. The other three bearings slide right in, so that would make sense. Anyways, it seems like they are going to take care of it...it's always nice to deal with a reputable business. Thanks again.

shane please keep us posted.

Where does the bearing insert hang up? If it binds up on the shoulders before it actually touches the journal, its an end-thrust problem. Either the bearing insert is too wide, or a crankshaft dimension is wrong. Sometimes these crank journals are re-welded in a past life and reground. This can make the width of the thrust journal too wide or too narrow, depending on how hung over the guy was that day.

Do you have the old thrust insert? Measure the shoulder thickness with a caliper or mic and compare to the new parts. Measure the overall width and compare that too.

chip

Shane:
I don't know for sure, but others probably know this. However, I faintly recall that the 235/261 is not bored straight thru when it comes to the main bearing mounts. I believe one of the bearing mounts is different from the others. Again, I am not sure of this or if this even makes any difference to your situation.

There are 4 different main bearing diameters on this engine.

Crankshaft diameter (standard size)
#1: 2.6835/2.6845"
#2: 2.7145/2.7155
#3: 2.7455/2.7465 (thrust bearing)
#4: 2.7765/2.7775

Oil clearance:
#1: .0005/.0033"
#2: .0005/.0033"
#3: .0005/.004"
#4; .0013/.0043"

Main bearing thickness (front-to-rear measurement):

#1: 1.098"
#2: 0.942
#3: 1.244 (thrust bearing)
#4: 1.224

Note: If the thrust bearing is a .060" undersize, the thickness is different, 1.256". Unless the crank has been ground WAY undersize, all the thrust bearings are the same thickness.

I don't have an end-play specification handy at the moment, but your machine shop should be able to check on it for you.
Jerry

Okay, talked with machine shop today and they have ordered another set of mains. I was incorrect, they are Federal Mogul, not Clevites...not that it makes much difference. Anywho, I am going to drop the crank by there tomorrow with the 'funky' set of bearings so that they may check the new against the funky and see if they can figure out the problem. I'll let you know how things pan out, but I expect it will be several days from now b/f I hear something.

okay, here's the update...took the crank to the machine shop and had them check it. Just needed about a thousandth or so worth of room. Minor, like all suspected. Since the crank has been turned twice now to date, the machinist opted to mill down the respective sides on each thrust bearing to get the clearance needed. End play is within specs. So what do y'all think? In addition, I put in the bearings this evening and placed the crank in position. It should be noted that I greased all the bearings above and below with some Engine Assembly Grease from Carquest. I understand this is like lithium grease and will break down as the engine is run in. My question is, how hard should it be to turn the crank? I am having problems getting it to turn in place and I am having a hard time getting the caps to seat flush with the block. I have read on previous posts were it is necessary to step the cap bolts to torque spec. Think I still have a clearance issue or do I just need to get the journals lubed first to spin it?

Did you put grease under the bearing insert? That would "tighten" up your clearances, especially if it was a thick paste. I use Lubriplate as an assembly lube. I don't put anything between the bearing and the block/cap.
Scott

Yup, I did...thought that might be part of the problem but couldn't decide if I was just being too safe or if the grease under the bearings really served a purpose. Guess, I should pull them out and clean and reinstall without any grease, how about a light weight oil?

48,

Nevermind, so nothing under the bearings, huh? Just want to make sure I have EVERYTHING lubricated and then lubricated again. Thanks for the input.

Yes, the back side of the bearings, (rod and main, BTW), need to be installed dry. This is necessary for proper heat transfer, as well as clearance issues. A bearing is slightly oversise, actually projecting above the surface of the block, and cap, and gets a "crush" fit as the cap is tightened. This is important to prevent the bearing from turning in the block or connecting rod. Put all the lube between the bearing and the shaft, none on the back side.
Jerry

Install the bearings as dry or dryer than possible. Use brake cleaner and get all signs of petroleum off. Might even use a little lock-tite, but I would'nt. The tighter the bearing is to the block/cap, the less likely you are to spin a bearing.
Scott

NOOOO!!!!! Never install grease, shims, lube, anything under the bearing shell. It'll cause bearing failure. Take it all apart and clean it good.

For that matter, did you clean the bare block when you got it back from the shop? Any block is full of metal chips and dirt when it comes back from a machining operation.

And the caps should slide over the crank journal and mate with the block saddles easily. Then tighten the main bolts in 3 steps of increasing torque.

Pull the crank and bearing inserts. Clean the hell out of everything. When I build an engine, I hook my garden hose to the hot water heater. I use Dawn dishwashing liquid and rifle brushes to clean every oil and coolant passage on my bare block. Then I immediately fog the block with WD-40, cuz the block is totally clean and will rust in a matter of minutes.

OK, OK... I've calmed down.....

When installing a crank with a neoprene seal, the crank should spin freely when torqued into place. You should be able to grab a counterweight and give it a one-handed tug that produces at least one full, smooth revolution. The crank should be smooth thru out the rotation, no binding or sticking. Using a rope seal makes it more difficult to tell, as the rope tends to bind up the crank rear seal surface and make it harder to spin. But it should still spin fairly easily. You shouldn't have to use the bolts to draw the cap down flush with the block. That means something could be terribly wrong.

Did you plastigauge the bearings? Do you know what the oil clearances for each bearing are? You must check the assembled oil clearance of each main and rod bearing, if you want it to live.

Not trying to down on you, but I've blown 235s up every which way to sunday. Trying to help you prevent some of the mistakes I made.

best of luck

chip

Yup, he needs a magnetic base and a dial indicator to check crank runout and end-play, once he has the crank installed.

One of my 235s died because of too tight main bearings. Another because of crank end-play due to improper crank machining. Another died because of distributor to oil-pump clearances. It pays to check everything.

And remember: Just because you're paranoid, doesn't mean they're not out to get you.

Main bearings are the trickiest part of a 235/261. These engines only have 4 mains, and they're under a lot of stress from the heavy rotating assembly.

chip

okay guys, thanks for that last round of input. I don't have the instruments you are talking about which is probably why I am in the dark in the first place. What I am thinking, and please feel free to retort, is taking the whole block back to the shop with the crank and having them check the clearances for me as they install the crank. Then, I can have it all documented by a machinist and hopefully avoid these issues of which you speak. I am not worried about handing it to these guys b/c they have communicated very freely with me and they have been willing to this point to work with me on everything to this point. I haven't gotten any bad feelings from them and I feel like I did a fair amount of research. Anybody's thoughts as to how far I should have them take the install? I was thinking just the crank to make sure it is properly done and then I could handle the rest from the cam on up. Thanks.