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All N-Series Tractors - Ford-Ferguson 9N, 2N, and Ford 8N


Engine rebuilding is already covered in detail, in the shop manuals, and on many other sites. I've provided a link to more detailed info near the bottom of this page.

Rather than duplicate all that information, what I will do here is provide a few tips that may not be covered in the other manuals. Compression checks should be done prior to deciding an engine rebuild is necessary. Some engine problems may appear terminal, but are easy to fix. My procedure for getting and interpreting compression numbers is here: Engine Compression Check.

IMPATIENT PEOPLE BEWARE - Rebuilding an engine is not particularly difficult. However, it is very meticulous work. Each step must be painstakingly completed, and re-done, as many times as it takes to complete the step successfully. Start cutting corners, and rapid engine failure is guaranteed. The point is that engine rebuilding requires patience! Some people simply do not have the personality/temperment to successfully rebuild an engine. This is not meant as an insult. I'm not entirely sure a thoroughly meticulous personality is a good thing. Any money saved doing engine work yourself instantly turns into a huge waste of time and money, if all the work has to be re-done.

ENGINE WORK - IN-FRAME or ON-STAND - It is possible to do an in-frame engine rebuild, but any tractor engine rebuild usually starts with removing the hood, battery, radiator, front axle, steering, dash,... With just a little more disassembly the engine can be placed on a stand. Some people have replaced main oil seals without splitting the tractor. That would have to be incredibly difficult, and nearly impossible to do a good job. By the time enough stuff has been removed to get access to either main seal, you are only about 6 bolts away from pulling the engine. Splitting a tractor is much easier than many people think. Go ahead, split the tractor and get that engine on a proper stand. It isn't absolutely necessary, but so much easier when the engine can be flipped sideways or upside down. It has gotten so my back protests leaning over anything for more than a few minutes. With the engine on a stand I can grab a folding chair and get comfortable. Keep an electronic or physical notebook of measurements. Take plenty of photos! It might be a while before this all goes back together. Why trust anything to memory when digital storage is basically FREE? Make sure your photos show things like which way the fuel valve is pointing, fuel line, and carb linkage routing.

PROPER TOOLS - Some special tools can be rented, but most rental tools have been abused past the point of being useful. A better option may be to buy any special tools needed and sell them when the job is done. Most people considering doing major engine work will already have things like: Torque Wrenches, Sleeve Pullers, Sleeve Drivers, Piston Ring Pliers, Ring Compressor, micrometers, ... You definitely should already have a set of flare nut type wrenches for the soft brass nuts on steel fuel and oil lines. Flare nut wrenches are basically 6-point box end wrenches with a slot just wide enough to slip over the fuel line tubing. The flare nut wrenches are also wider than standard wrenched, so they bear on more of the hex head surface. A good set of inside micrometers can be used to measure cylinders. A cylinder bore gauge with a dial is better. Measuring critical dimensions with more than one tool can find errors and avoid serious mistakes.

SIDE JOBS - While the engine is in pieces, there should be plenty of time to deal with anything else that affects reliability. Send the radiator out to be cleaned, tested, and re-cored if necessary. Repairing an original radiator is far better than trying to fit most of the new replacement radiators. Buy new radiator mounting hardware, and rubber pads. Do you need a new radiator cap? Check condition of hoses, hose clamps, and thermostat. Store associated parts with the radiator, so they won't be lost when it's time to put everything back together.

Completely drain the fuel from the tank, remove the fuel valve assembly, and twist a pipe plug in the hole to keep things out of the tank. Leave the fuel valve on the tank and it will surely get broken. Check inside the tank. If it is rusty, now is the time to deal with that. A handful of gravel and a couple gallons of water can loosen some nasty accumulations while the tank rides around in your trunk for a few days. There are products that can be used to clean and coat the inside of a rusty tank. Make sure the product is good for ethanol-blended fuel.

Replace Rotten Hardware -

Remember those rotten little nuts and bolts that held the dog legs to either side of the hood? Now is a good time to match those up with new zinc plated hardware. Put the new bolts through the holes in the dog legs, or tape them in plastic bags to the inside of each part.

Stuck Fasteners -

Dealing with frozen or stripped nuts and bolts is not covered in any manual. I love it when the manual says something like "remove left whatsit". A simple step that appears to be worth a minute or less often turns into 3.7 hours just to remove one stripped or stuck bolt. PB Blaster works much better than anything else for rusty hardware, PERIOD. None of the other products, or home-made rust dissolvers worked as well as PB Blaster in any of the actual side-by-side comparison tests I have been able to find. Remember heat causes metal to expand. Heating a nut will expand it away from the bolt and may help break it loose. On the other hand, heating a bolt expands it into the threaded hole or nut, and just locks it even harder. If you use heat on a bolt, wait until it cools completely before trying to turn it. I often start spraying rusty fasteners with PB Blaster a day or longer before attempting to move them. Rusty stuff might get sprayed 2 or 3 times, before making the first attempt. The chemicals in PB Blaster work best when given more time to work.

CAUTION ! - Do not breathe fumes from heated parts that have been soaked in any chemicals!

Rusty Slotted and Phillips machine screws suck. Most of those screws are not coming out with regular screwdrivers. You can try, but don't twist so hard you completely wring the slot out. If you've already mostly ruined the slot before finding this site, don't give up yet. Before you start drilling them out, get an impact driver. Not an air gun, get the old-school, whack-it-with-a-hammer, manual impact driver. Buy a medium-weight machinist hammer also, if you don't already have one (about 3 pounds with flat and ball peen striking surfaces). You are working on a Ford, so I assume you already have a full set of various hammers.

My impact driver is a Sears Craftsman from my motorcycle days. An impact driver is a miracle cure for stuck and stripped machine screws. The tool and bits are hardened steel, and the tool has an internal taper that works in both directions. Some screws break loose easier if the first attempt is to tighten them slightly. Place the bit in whatever is left of the slot, turn the tool less than 1/8 turn up the ramp in the direction you want the fastener to turn, then give the tool a good firm whack with a medium-size hammer. Do it again, and again. Hit the tool, not your hand! The hardened steel bits will usually improve whatever remains of the original slot or even get a new grip. By the third good whack, the screw should start to turn. Keep going for a few more whacks turning the tool a little more before each whack. Switch to a standard screwdriver and back the screw out once it's good and loose. You just saved the threads from a lot of abuse caused by drilling and re-tapping.

The combination of impact, and a little nudge in the right direction will loosen most stuck screws, even when the head has been thoroughly stripped and looks hopeless. Get in the habit of using the manual impact tool to loosen all machine screws. Damaged screw slots will soon become a thing of the past.

An assortment of nut splitters, saws, chisels, grinders, and a cutting torch may come in handy when rotten hardware will be replaced anyway. It is especially aggravating when a previous owner used extra long bolts rather than buying or making them the correct length. Sometimes the easiest way to remove rotten hardware is to over-tighten stuck fasteners till they snap.

There will be bolts or studs that snap-off flush with a casting surface. I've only rarely had success with "Easy Outs". They may work if the snapped bolt wasn't torqued to the bottom of the hole or available threads. If you try an Easy Out, use the largest drill bit and Easy Out that will fit in the snapped bolt. Do not snap an Easy Out off trying to break the stuck bolt loose. That just makes a bad problem worse. The hardened steel Easy Out is nearly impossible to drill. Any snapped hardware that is bottomed in the threads or otherwise completely stuck, will have to be drilled out. Center punch the bolt. Start with a small bit. If the bit goes off-center, angle the drill, then straighten out, so the hole ends up in the center of the snapped bolt. It is very important to drill as close to the center as possible. Use larger and larger bits until most of the bolt material is gone. Use a pick to clean the bolt threads out of the threaded hole. Finally, run the correct size tap through the threads to clean the threads.

Some people recommend using "thread chasers" to clean threads rather than a tap. There are plenty of thread chaser kits being sold and plenty of arguments for using them rather than a tap. The thread chasers are said to be made with less aggressive cutting edges and smaller diameter so they don't damage threads. The claim is that a tap can't be perfectly aligned with existing threads and threads get smaller and weaker every time a tap is used. Baloney! If a tap doesn't have to cut new threads, it will always take the path of least resistance unless forced. Be gentle and a tap is completely self-aligning. Be a gorilla and anything can be cross-threaded.

Machine Shops -

Major engine machine work should be done by a specialized engine machine shop. Machine shop time and equipment is expensive, but worth every nickle for engine work. Any disassembly and assembly work you can do will save money. The line between major and minor machine work varies widely. Some fortunate individuals have a full machine shop at home, and still don't attempt engine machine work. This is definitely a specialty that requires special knowledge and tools.

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9512 Woodman Rd
Richmond, VA 23228

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Laurel Auto is the engine shop that did machine work for two sleeves on my Ford Flathead V8. Talk to Greg, either one. It's a blessing to find good people, who know what they are doing.


Proper tools is essential especially for engine work. Special tools include: Inside and outside micrometers, ridge reamer, cylinder hone, plastigauge, ring compressor, gear puller/balancer removers.

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Some tools can be borrowed from an auto parts store. The usual deal is they charge you full price for the tool. When you bring it back you get most of your money back. If you keep or destroy the tool, they have already been paid the full price to buy it.


This is my shop press. It might be possible to do without one. I don't remember not having one. This was purchased from Harbor Freight many, many years ago. With heavy use, the hydraulic bottle jack lasts about three years. I've rebuilt and reconfigured this press twice. It looks very little like the one I bought.

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Sort and Store Hardware - Pay close attention to which bolts go with which holes. Some hardware for attaching the cylinder head may use nuts and studs. Take pictures and notes to ensure the correct hardware goes back into the holes. If you use a bolt or stud that is too long, it will crack the engine block when it bottoms out in the drilled hole, or if the unthreaded portion of the shank jams. There are many types of hardware bins, cans, jars, or even Tupperware that can be used to keep track of hardware. Buy your own Tupperware, don't raid the kitchen cupboard.

If you are replacing the cylinder head, the new heads are generally somewhat thicker castings than the old ones. That means you will need new longer bolts, or longer studs. The cylinder heads on all 9N and 2N tractors were originally installed using studs and nuts. Studs cause much less wear and tear on the threads in the block. All the wear occurs when the nuts are tourqued. The parts manuals say the stud lengths were 15 short, 2 medium, and 1 long. That's not very helpful for anyone shopping studs or bolts. The 15 short studs were an odd 2.78" length. The 3 longer studs were actually 2.9" and were only longer so there was room for a second nut to attach the wire tube to the engine. All 8N engines used 18 bolts that were a non-standard 2-3/8" long. Most people wou use bolts buy 2-1/2" grade 8 bolts and use a grade 8 washer to reduce the length closer to 2-3/8". The hex heads are a smaller size, so the washers also help spread the clamping force. The factory changed to bolts, so bolts are ok. Studs are simply better, but a royal pain to work with. Studs should be turned into the head to the full depth of the available threads finger-tight. When the gasket and cylinder head are placed on the engine, studs that are too long or short are immediately obvious. If the unthreaded shank is sticking up above the head, the stud is too long. When the nuts are tightened, studs cause much less wear to the threads in the block. There is absolutely no need to "lock" studs into the casting by cranking them until the unthreaded portion jams. All this does is make the studs harder to remove.

If your cylinder head was attached using studs and nuts, the original studs can usually be re-used, I generally do not attempt to remove any frozen studs, unless the deck surface needs to be machined. In that case, I may just let the machine shop deal with stuck hardware. It's way too easy to snap them off.

Likewise, the studs to attach the intake/exhaust manifold can stay in place unless the threads are in really bad shape. That should not be the case since the manifold nuts are softer brass metal. Any thread damage usually occurs at the nuts. DO buy a new set of brass manifold nuts.

All studs or bolt threads must be sealed with permatex where the holes go into the water jacket. Most of the head bolts and manifold bolts go into the water jacket.



Any work on the rotating assembly (crank, pistons, camshaft) should be done on an engine stand. It is so much easier if the engine can be rotated. Definitely get one that has four wheels, it is much more stable than the three wheel version. Even with the four wheel version, be careful!

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Before doing any disassembly of the rotating assembly, move each rod end side-to-side, and see if any are looser than others. If you find any that are loose, remove those caps and inspect the bearings. Look for obvious damage. Spun bearings will probably have melted and become metal flakes in the oil pan. Look at crank journals and bearing seating area in each rod. A dial caliper or micrometers can be used to determine if bearings that look good still need to be replaced. Any obvious grooves on the crank journals will mean the crank needs to be regound or replaced. Damaged rods will have to be replaced.

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This is never as simple as what is printed in the manual for a flathead engine. "Pry out the valve guide bushing retainers" is what the manual says. That seems simple enough. No doubt, when they wrote the manual, it was just that simple to pry the retainers out.

The manual falls way short of the actual effort necessary to get the valve guide bushings to move at all in a 60 year old engine. The engines we are working on have years of rust, varnish, and goo. Most of the bare metal valve guide bushings will have become completely frozen to the engine block.

The valve guides are part of the valve assembly that was originally slipped down into the block and secured in place with a steel clip. Once that clip was inserted, the valve guide moves up slightly trapping the clip in the block. The valve guide bushing needs to move down slightly in order to release the retainers. In a new engine, prying on the small hole in the retainer is enough to move the bushing down and release the clip. This is what the manual says to do. Good luck with that.

Look through the intake and exhaust ports. The top of each valve guide bushing should be visible. It may be possible to take a pry bar and pry them down enough to remove the clips. The valve guide bushing retainers should move down fairly easy against the valve spring tension. I usually find about half or more of them are completely frozen in the bore. The engine I am disassembling as this is written had all of the guides rusted to the bore, and the retainers thoroughly rusted to the slot in the guides. Soak them in PB Blaster, automatic transmission fluid, or whatever rust-dissolving product you prefer to use.

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This is actually a Flathead V8, not the 4-cylinder, but this photo graphically illustrates what might be found when the valve comes out. The clip would not move, so I compressed the valve spring UP, released the valve spring retainers, and worked the springs out of the way. It was then possible to pry the valve stem UP, and eventually pull the valve out of the valve guide.

Removing the valve exposes the top of the valve guide, with plenty of room to swing a large hammer and punch to knock the guide down into the lifter valley. In this case, I first had to remove an old pack rat's nest, and clean out many years of nasty stuff before the valve guide was visible. Before getting out the big hammer, hose the stuck guide down with ATF, PB-Blaster, or whatever special formula you like to use on rust, varnish, and goo. Then walk away and do something else for a while. I soaked mine three times before attempting to move them.

A short piece of 1/2" black iron pipe makes a good punch that won't ruin the valve guide if the plan is to re-use them. These were probably not going to be re-used in this engine, but some of them might be good for another engine if I don't mess them up any worse.


My favorite Ford tool (the 5 pound mini sledge hammer) is used a lot more often than I should admit.

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Tag the valve assemblies, or store them to keep all the parts for each assembly together. If they are being re-used, each valve assembly needs to go back into the same hole it came out of.

Check each valve assembly, valve sealing area, and the valve seats in the engine. Look closely for signs of mis-matched parts, broken springs, burned valves, and any other problems.


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CLEAN, CLEAN, then CLEAN AGAIN - Do not assume that any parts the machine shop had have been completely cleaned. Thoroughly wash and clean out all cylinder bores and oil passages, then clean them again. Wash means using plenty of hot soapy water until a white rag stays clean. Immediately apply oil to all bare metal to prevent rust.

Oil Gallery Plugs - There are one or two small plugs near the camshaft that plug the ends of the main oil passage through the engine. They must be removed to thoroughly clean the engine block. My early 9N engine block only has one plug at the front. My 1951 8N side distributor engine block has one plug at both ends of the main oil gallery tube. The parts books point to the front galley plug with part number 6397. This is wrong. Part number 6397 is the dowel pins that help locate the front cover and transmission. The correct part number for the gallery plugs is 3563052-S5. If you have to drill yours, you will need to buy a tap. The plugs are standard hardware, 1/8-27 NPT pipe plug 3/8" long with a slotted head. That fine-threaded 1/8-27 pipe tap probably will not be in your set. It might be easier to find the plugs with an allen head. If so, the next person to work on that block will thank you for changing them. Do not attempt to remove these plugs with a standard screwdriver, loosen them first with a manual impact driver, as described above under "Stuck Fasteners".

ENGINE OIL PUMP - The oil pump innards can often be replaced to repair any wear. If the pump casting is badly worn, scored, or cracked, it will have to be replaced. The oil pump is part of the main bearing cap on the N-Tractors. It the main bearing cap/oil pump is being replaced, the block and all main bearing caps will have to be line-honed.

Carefully inspect the pump pickup tube. They occasionally come loose at the oil pump and start sucking air. The oil pump can lose prime. Running the engine without oil pressure will very quickly ruin the bearings. If there is any question about the connection of the oil pump pickup, braze it again to make sure.


You may elect to have the machine shop remove and install sleeves, or install the entire rotating assembly for you. Keep in mind that you will have to pay for the service. Anything you can do yourself saves money, unless you mess it up. There is not much I can add to the process of removing and replacing piston assemblies, sleeves, crank, and bearings. The work is already well covered in the shop manual and other guides. Do use plastiguage on every crank and rod bearing to confirm clearances before bolting the bearing and rod caps for the last time.

Use Permatex Sealant on studs and bolts that go into the engine - Many of the studs/bolts that go into the engine block go into the water jacket. If there is any doubt, apply sealant to the threads of these fasteners.

ASSEMBLY LUBE - Use plenty of assembly lube and motor oil on everything as it goes together. Assembly lube is for bearing surfaces. Motor oil should be on the cylinder and pistons. If this engine is going to sit for several months before being fired, use something a little thicker like STP on the pistons and cylinders. Over time, motor oil runs off and disappears. Starting a dry engine is very bad.

MAIN OIL SEALS - Crankshaft rope seals are a pain. There is a upgraded rubber lip type seal for the front main crankshaft seal. I believe the rope seal is all that is available for the rear crank seal. Some people have replaced oil seals without splitting the tractor. That just seems like it would make a difficult job nearly impossible. With the engine on a stand I can be sure the job is done right. I can pull the pan, check the oil pump tube, and replace the rear seal. The front seal actually seals to the crank pulley, so when the crank pulley is removed there is a little gap. I don't think that gap is wide enough to get the old seal out and new seal in without at least removing the timing cover. A sneaky-pete tool might pull the seal outta the oil pan groove but I usually end up gradually destroying the old seal rather than getting one nice big piece pulled out. I prefer to use a one-piece seal on the front if I'm using a new crank pulley. Some of the one piece seals come with a renew sleeve, that provides a new smooth seal area for the crank pulley. If my crank pulley is bad enough to need one of those sleeves I'm just going to use a rope seal that will conform to whatever grooves are on the sealing area. Carefully cut the rope seal lengths to fit exactly flush in the top and bottom half. Do not be tempted to leave the seal slightly proud of the surface! That will surely crack the seal retainer flange and result in a seal that leaks.

CHECK FOR PROBLEMS DURING ASSEMBLY OF ROTATING PARTS - Place a standard 1/2" drive breaker bar on the front crank bolt and turn the crankshaft after each bearing cap is tightened in stages. I start with about 1/3 the recommended torque, then 2/3, and a final pass to the proper torque. If there is ever any sudden increase in effort to move the crankshaft, STOP! and figure out why. The crankshaft should get gradually harder to rotate as each bearing is tightened, and as each piston assembly is added to the rotating assembly. When complete, the crankshaft should still move by hand without too much effort.

When you are finally ready to install the engine in the tractor, if it has been on the stand for a while, put a quart of oil in the pan, and turn the engine upside down a few times to distribute oil into the cylinder bores and around the camshaft.

Once the engine is installed, fill the crankcase, and prime the lubricating system by rotating the engine oil pump. Exactly how you do that depends on how the oil pump is driven. Some oil pumps can be turned without turning the engine. On the N-Tractors the oil pump is driven directly off the crankshaft. Remove the spark plugs and crank the engine a few turns. Make sure you see good oil pressure on the gauge before putting the spark plugs back in.
I generally use a 10W-40 "starburst" SM motor oil that lists some level of ZDDP on the label, then use an oil additive product that brings the ZDDP level up to a level similar to that formulated into the older type SF or SG motor oil. At this time STP Oil treatment is what I an using. Here's a link to a longer blurb about motor oil and ZDDP in Motor Oil.

Link to Complete Engine Rebuilding Info

This is a link to the How-To articles area on the N Tractor Club web site. Look under "ENGINE" on that page, and you will find a comprehensive list of how-to articles.

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Save this link! The How-To area at ntractorclub.com has a lot more than just engine rebuilding info.

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