Engine Bearing Replacement

[HydroPuddle]

I have a 1943 Ford 9N. I have taken the engine all the way down to a bare block and I am ready to purchase new bearings all around. The shop manual (Paragraphs 40-43) is very handy when it comes to describing how to check if you need new bearings but it's a little unclear to me when you plan on replacing them regardless. There is some wear on the middle main and it may be Ok but I don't want to put this thing back together without fresh bearings.

I checked for out of round at the bearing surfaces on the crank and all are within spec and are less than .0015 inches out of round when doing the four measurements as described in the shop manual

Somebody has for sure been in this engine in the last 70 years, there must be four different types of valve manufacturers in there and I suspect due to the generally good condition of the bearings themselves and the uniformness of the crank, it may have been ground in the past.

To start, and as reminder, the stock tolerances direct from the manual...

Stock Mains: 2.248-2.249 inches (57.10-57.12mm)
Wear limit: 0.005 inch (0.13 mm)

Stock Rods (Crankpin): 2.0935-2.0945 (53.18-53.20mm)
Wear limit: .005 inch (0.13 mm)

This is what I measured on my crank...
My Main Front: 2.230 inch (56.65mm)
My Main Mid: 2.230 inch (56.65mm)
My Main rear: 2.231 inch (56.67)

Rod 1: 2.0767 inch (52.75mm)
Rod 2: 2.0763 inch (52.74mm)
Rod 3: 2.0755 inch (52.72mm)
Rod 4: 2.0755 inch (52.72mm)

I just want to make sure I got this right. If I subtract my measurement, from the the tolerance on my front main I get...
2.248 (low stock) - 2.230 (My Front Main) = .018
2.249 (high stock)- 2.230 (My Front Main) = .019

The question is... Which main bearing kit size should I buy? .010, .020, .030? Should I suck it up and pay somebody to grind the crank?

Thanks in advance...

 

[Skip Burney]

If you put new bearings on an unground crank you will end up right back where you started. The only way I put new bearings on a crank that hasen t been ground is if the machine shop says all it needs is polishing. The unground crank will quickly wear the new bearings to match it.

 

[teddy52food]

Is the crank cleaned up good so you can see if it is stamped? I would guess it has been ground to .010 and worn another .008. It needs to be ground to .030, as it is worn too much to go to .020. Unless your mike is way off. Can you measure where there is no wear?

 

[HydroPuddle]

I think I'll just have it ground. I should have just changed my rings and got it back together but I found some burnt valves and the scope creep just kept coming.

I really need my tractor right now. This has been a crazy winter and my roads are getting so bad I can barely make it up the hills in full size 4wd. Some of the neighbors haven't been able to use their cars since before Christmas. The ice ruts are so bad most cars will high center.

Im trying not to cut corners but I can't even get UPS or FedEx deliveries right now. I didn't realize how much we really need that thing to run until it finally lost compression and refuseUd to start. It gave plenty of warning signs but there never was a good time to rebuild it.

 

[HFJ]

hi hydro

a 1943 is actually a 2N. all 9N [i:60c195309e]and[/i:60c195309e] 2N serial numbers start with "9N"

i used to think the sequence of 9, 2, and 8 indicated the people who chose the numbers worked in a poorly ventilated area with rude and volatile organic solvents.

then i found out it was actually 193[b:60c195309e]9[/b:60c195309e], 194[b:60c195309e]2[/b:60c195309e], and 194[b:60c195309e]8[/b:60c195309e] - the years each model was introduced.

 

[ASEguy]

The back of the bearing will give you the undersize on it. If it's not grooved and the old bearings look good either get the same undersize or put the old ones in. I would replace them if it were mine, but I can't see the bearings either.

 

[Ken(Ark)]

I think I'll just have it ground.

If money is tight slap it back together and it will run 5 - 10 years . If you have money to work with take your head , valve train , block and crank to a reputable machine shop who can tell you ( no guess work ) if the crank just needs polished , ground , run as is .

These motors are very forgiving . You can shade tree a rebuild and get by for a long time , you can spend $2k and have a perfect motor that will probably last longer than you will , or any level in between .

Is your budget tight , how much land are you working , is this your only tractor , what is the overall shape of the rest of the tractor , how long do you pan on keeping it ?


If you are working 80 acres + then patch this one up and trade it for something bigger . You can spend $2k on a motor but your trade value is never going to be over $2k .

If this was your Fathers tractor and you are going to keep it until you die , spend the money .

If you have 3 - 5 acres this is probably the only tractor you will need .

 

[souNdguy]

check the bearings you have with plastigauge. ( see if they are still in spec )

as a default, you know if you slap in a new set of what it had.. they will fit.

If the old ones are not out of spec, and you know new will fit in.. ... there ya go.

 

[HydroPuddle]

Questions answered and some comments commented upon...

Yes, this is my only tractor. I don't have much land but I maintain about half a mile of dirt roads on steep grades. It usually takes me 2 hours with a back blade to make it perfect after a big storm and maybe 30 to 45 minutes to clean it up every few weeks. When we have a big storm it's not uncommon for massive amounts of dirt several inches thick to flow out onto the the paved highway. Although we haven't been fined, it's dangerous to hit that kind of thing at speed. My dilemma is the big melt is coming and it's not the kind of thing that can be done with a shovel. I supposed I'll just rent a skip loader or something.

The plan is to keep my tractor till I die. Every piece I've taken off has been stripped primed and painted. Every part that is not perfectly serviceable has been replaced. I actually prefer parts that that are beat up but still work exactly as designed ("honest and earned") but I worry that places like Yesterdays Tractor may not exists in 40 years.

2N versus 4N. I can't always remember years, I'm highly dyslexic. I did look up the serial number when I first got the tractor and confirmed it was a 9N not a 2N. It's a '42 or earlier. I've worked on a couple of different N series and I get confused sometimes. Ask me what I think about fractions!

The more I think about the crank... I just can't let it go.I'm going to pull every stud and send the crank, the cam, the block and the head out to the machine shop. I want it to be mechanically perfect.

I'm going to post another question about sleeves here in a minute. I'm going to carry on with replacing or refreshing everything on the inside.

 

[Kenockee 8N]

When is the next time you plan on having the engine apart and why is it apart now?

If you are going to be in the engine often, re-using bearings or putting new bearings in on a untouched crank "can be OK." There may be life left in them and if you are going to be apart new year or something like that, it could be changed at that time.

If you never plan on being this far into it again, or it is apart because of a main or rod bearing issue, then I would at a minimum have it checked out at a reputable machine shop. While it is this far apart, you may as well have some peace of mind knowing that going back together, things are right.

 

[Bill M. From Illinois]

I think it best to have the crank and rod ends checked by a regrind shop. Mine cost about $100 and he ordered the correct bearings which were
no more expensive than getting them myself. He may need to add metal and re grind the center bearing to keep crank from lateral movement.

 

[HydroPuddle]

I'm gonna go have it looked at by people who know and spent more than $8 on a mic.

I did double dog check to verify my tractor is a 9N. It's serial number 9N90717. Should be a 1942 and built 6 years before my mom was born. It boggles my mind that things built that long ago last so long.

Thanks for everybodies replies.

 

[HFJ]

i spent 10 on mine. how flexible are u on the "people who know" part?