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Fordson Tractors Discussion Forum

Main Bearing Size ????

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Ramp Rat

09-07-2010 07:07:45

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While replacing the rear main oil seal on an NAA I noticed that I should be planning on turning the crankshaft and replacing the bearings.
Trying to figure if my crankshaft has been ground down I looked at the numbers on the rear main bearing. It doesn't state any size but has the following info: "Clevite 77 7 79 MB 1501 P".
Can anyone tell me if this is STD, .010, .020, etc?
Thanks, Steve.

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Earl -IL

09-09-2010 15:45:50

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 Re: Main Bearing Size ???? in reply to Ramp Rat, 09-07-2010 07:07:45  
Very few shops have a hardness tester.But I have found that if you check the hardness of the crank and it checks OK & the size & and oil clearance is correct bearing failure is usually contributed to engine assembled dirty, Pre lube was overlooked. On a major rebuild we always prelubed on assembly plus we used a Federal Mogul pressure lube tank.Rotating the engine until oil came up to the valve train.It takes a long time for oil to get to all the parts of a engine that is completly disasembled.This is only a few reasons for bearing failure. Engine class 101 is that bearing suppose to rub on the crank???

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Robert Major

09-09-2010 18:59:38

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 Re: Main Bearing Size ???? in reply to Earl -IL, 09-09-2010 15:45:50  
Hi Earl I get what you are saying about the oil and stuff. I am a full trained Agricultural engineer on farm tractors and equipment. I have been re building motors since I was 12(24 yrs)I pulled the pan and caps off this 6d as she had low oil pressure the shells are un marked and measure pretty good compared to some new ones i have on the shelf. The problem is she is so soft that there are ridges worn in where the oil groove is on the mains. I guess apart from the crank being oval 40 shells would go straight on. I know the guy that did the original rebuild and he would of done everything by the book.Lube and cleaning would of been spot on. I asked my crank guy and he said those ford motors like mine are not too good past 20 -30 thou. he had problems with the 4cyl majors in the 60s when he started out and they needed the first rebuild. Like you say there are loads of things to take into account but hardness sounds like a fordson problem from what ive heard from a relible source.
Regards Robert

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Earl -IL

09-11-2010 07:30:52

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 Re: Main Bearing Size ???? in reply to Robert Major, 09-09-2010 18:59:38  
Hi Robert, You keep refering to a 6D engine. Looking through my Bearing spec manuals what is this engine used in ? Tractor, truck or industrial. The reason I ask is back in the 1960's? my father had a neighbor that farmed with Majors, 4cyl. He installed 6 cyl Dexta in those tractors and out performed the 4010 Deere on power & fuel economy. I remember talking with him & he told me he was lacking on the hydralic system. He passed away several years ago & I was told those 2 tractors along with some of his machinery was still in the machine shed.Maybe you can shed some light on this conversion. I believe the engines came from some Ford trucks that were special orderd for this RC Cola delivery, here in Illinois. Are you aware of the Distributor of Dexta parts in Wisconcin, I looked for his parts manual,I think I loaned it and never got it back.

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Robert Major

09-11-2010 12:51:07

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 Re: Main Bearing Size ???? in reply to Earl -IL, 09-11-2010 07:30:52  
Hi Earl. There is not a 6cyl dexta motor made. I am asumeing that those trucks had the ford diesel and not a perkins with adapter plate to fit the ford gearbox bellhouseing as some guys put perkins in as well. the old fordson E27n (or long horn as it was called in Canada) had those fitted from factory or DIY conversion . The 6d motor is the 6 clylinder version of the fordson major tractor engine. They where a UK made truck motor and are some times refured to as dover and later ones being dorset. ( named after English countys) with aplication in ford thames trader (dorset later ford cargo) trucks, combines industrial aplications, and roadless /county 4wd conversions in the late 50/60's There where never any genuine fordson new type majors with 6cyls and 2wd released as a fordson factory fit they are all home built conversions. . Those motors are the grandfathers of the ford 2700 Dorset range of motors that are in newholland 642 1400 and tr70 combines! I guess if you search the gallerys of pictures on here for the early 60 s county super 6 you will find some pictures of the motors in tractors. The conversion is not that hard to do the top of the bellhousing of tractor and truck are the same so bolt right up. the oilpan is slightly different and some holes dont match but most guys dont worry about that. the frame rails hood and steering link on the tractor are lenghtened about 11-12 for the extra 2 cyls. The front axle A frame is either turned round and shortened to poke out the front with a bracket on the tomb stone, or a u bracket is made to run under the motor and oil pan to support the frame in the stock location. The truck pan is aluminium with no mounting lug cast in against the tractor pan being steel with the lugs. I could well believe that they hammered the JD in power and fuel it is around the 80 -90 HP mark as well. yes i would believe the JD hyds would hammer the major though it was a lot better pump. I have built a few of these in my time back in England. I have a power major with this conversion That I bought over from the u.k that my friend did in the 60,s .A super major that I am putting a ford 2704et dorset in she is around 150hp!. We tractor pulled these majors back in the U.k and got upwards of 500hp out of them with a lot of know how. If you get on youtube atall there are loads of video clips on there of them pulling that kinda HP. I would love to see some pictures of those old majors if they are still there. It is an expensive conversion to do now as most guys in North america want $4000 for a 6 cyl motor to do it. Unfortunately I an up in Canada so have no Idea on dexta stuff in the U.S. I would try ebay and see what turns up there or on the general internet as there are loads of guys selling repro parts and manuals for these tractors around the world. I hope this helps you out with some of what you wanted to know. Regards Robert

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Ramp Rat

09-09-2010 16:00:23

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 Re: Main Bearing Size ???? in reply to Earl -IL, 09-09-2010 15:45:50  
Thanks Guys, That's why I asked about grinding a crank to .040". Not only the strength of the crankshaft but how far into the metal was the nitrite?
I'm an aircraft mechanic and when we have a crankshaft turned, if it's even allowed for a given engine, the shop has to re-nitrite the surfaces along with other tests. Same problem with refacing valve lifters. You can remove the hard face real easy.
Thanks for all the info. The engine will be my next worry. Right now I'm waiting for a pilot bushing to be made from back east. Seems my NAA doesn't have the common bearing but a bushing. :-(

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Robert Major

09-09-2010 22:36:21

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 Re: Main Bearing Size ???? in reply to Ramp Rat, 09-09-2010 16:00:23  
I have talked with a couple of guys that wrench on planes. yeah they are pretty strict on the procedure for what you can and cant do. But guess they have to be as I would not want some piece of junk plane falling on my head when it went south.The other thing is that if it stops you cant pull over and lift the hood take a look then phone the tow truck. some of this stuff and rules would drive me crazy. Im glad you have more patience than me. I have got to put 90 needle rollers in a planetery hub tomorrow "probably nearer 190 by the time they fall out and i get it right!". maybe you should come do that for me?. Regards Robert

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09-08-2010 15:25:29

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 Re: Main Bearing Size ???? in reply to Ramp Rat, 09-07-2010 07:07:45  

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Ramp Rat

09-08-2010 16:19:51

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 Re: Main Bearing Size ???? in reply to wilder11354, 09-08-2010 15:25:29  
Cool, than I have room to have this crankshaft turned when I get ready. ;-)

BTW, I've noticed that there are bearing sets sold for .040" undersize???? Can this be true???
Is a crankshaft turned that much worth while?
Thanks, Steve.

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Robert Major

09-08-2010 20:36:20

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 Re: Main Bearing Size ???? in reply to Ramp Rat, 09-08-2010 16:19:51  
Hi steve Not wanting to tread on the toes of the retired crank seems to depend how far the hardening goes into the crank. I have a fordson 6D motor that is at 30 thou and the hardness is all gone she has cut ridges in the crank in no time. 40 over is a waste of time for this but you can buy shells. I have to get her spray welded and bought back to new spec as it wont last again. I think there are some perkins out there that dont take to kindly to grinding atall. It seems that my crank guy has 40 plus under the belt too and experienced a lot of different stuff. He will just say dont bother to bring it just bin it on certain things when I ask. Regards Robert

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Earl -IL

09-08-2010 19:16:51

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 Re: Main Bearing Size ???? in reply to Ramp Rat, 09-08-2010 16:19:51  
If brg manufactures make the bearings, its OK to grind. I have run a crankgrinder since 1957.retired in 2001.

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Earl -IL

09-07-2010 19:06:41

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 Re: Main Bearing Size ???? in reply to Ramp Rat, 09-07-2010 07:07:45  
Take a brg shell to a machine shop that does crank grinding they have the spec for the bearing thickness & can tell you if it is undersize. You have to have a ball micrometer to get a accurate reading.

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