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Rebuilding The Ford 4.0L Pushrod V6
Doug Anderson, Automotive Rebuilder, April 2001
The Ford 4.0L/244 cid is the big brother in a family of Ford V6 engines that were built in Cologne, Germany, and have been used in domestic Fords since the early ’70s. The original 2.6L engine was replaced by the 2.8L, which was upgraded to the 2.9L and then finally bored and stroked to make it into the 4.0L that was used in the Rangers, Aerostars and Explorers starting in 1990. It was replaced by a SOHC engine from this same family at the end of model year 2000.
These pushrod engines are all conventional 60° Vs with cast iron blocks and heads. The 2.6L block that began with a 3.54˝ bore and a 2.63˝ stroke ended up with a 3.952˝ bore and a 3.307˝ stroke by the time it grew into the 4.0L. The block was just about maxed out at this point, so the cylinders ended up pretty close together, and the rods were crowding the pan rail, especially on the 97TM blocks.
Some rebuilders have commented that making the 2.6L into a 4.0L was a lot like making the 265 Chevy into a 400; it’s a good analogy on a slightly different scale.
Ford has made a number of changes and improvements to the 4.0L since it was introduced. Engineers revised the block, changed the heads, played with four different cams and used four different rods, so it would take about 10 short blocks and even more long blocks to rebuild all the combinations exactly the way Ford made them over the last 11 years. With all that in mind, let’s take a look at the 4.0L and see what Ford has done to make life more interesting for the rebuilder.
1990-’95 and ’96
We had always believed that this change took place sometime during model year ’95, but my best sources tell me it was actually made late in calendar year ’95, which means it was a model year ’96 change. The front of the crank had to be modified to accommodate the additional gear that was needed to drive the overhead cam for the SOHC engine that was going to be coming out in ’97, so the change was made during model year ’96 to standardize the process ahead of time.
About 25% of the ’96s were made with the 90TM crank that had the short keyway in the snout and 75% were made with the 96TM cranks that had the long keyway, but we’re told that there were also a few engines built with the 90TM cranks that were machined with the second step and the long keyway, so it’s best to double check all of them before using any of them.
Understanding this mid-year change helps explain the mix of castings that we have seen in these engines, but it really doesn’t make any difference which crank you use in a ’96 as long as you use the matching crank gear. However, it could become an issue when selling a crank kit because the gears are not interchangeable, so you have to know which one the customer has in order to supply the matching crank. Otherwise, you will have to specify the gear that needs to be used with the crank that is actually boxed in the kit. It’s probably a good idea to include the matching gear or some information explaining the differences along with the crank kit in order to avoid any problems in the field.
All of these cranks had a six-bolt flange for the flywheel.
1990-’94 Ranger, Explorer and 1990-’96 Aerostar
1995-’97 Ranger, Explorer and ’97 Aerostar
1998-2000 Ranger and Explorer
Which cams can you interchange? That all depends on who you ask. Some rebuilders are building every application by the book, some are consolidating the FOTZ-B with the F3TZ-A and keeping the other two applications separate, and others are combining the FOTZ-A and the FOTZ-B with the F3TZ-A and keeping the F3TZ-B separate. All of the aftermarket cam suppliers I have talked to are providing three cams, one to replace the FOTZ-A, one that splits the difference and combines the FOTZ-B with the F3TZ-A, and another that replaces the F3TZ-B.
There’s one more consolidation that seems reasonable based on what we’ve learned:
Throw away all of the FOTZ-B cams and use the FOTZ-A for everything from ’90 through ’92 and for all of the ’93-’96 Aerostars. The FOTZ-B is very similar to the FOTZ-A, except that the timing was advanced 10° to move the torque curve around in order to make it feel a little better with the manual transmission, so the FOTZ-A should work fine with a stick; the difference is so slight that it probably won’t even be noticed. We wouldn’t recommend using the F0TZ-B with an automatic, though, because the extra advance in the cam may affect the way the engine behaves with the torque convertor, so you should throw these cams away if you’re going to consolidate all of these engine applications.
Use the F3TZ-A for the ’93-’95 Rangers and Explorers that don’t have EGR; and
Use the F3TZ-B for the ’93-’95 engines that came with EGR and for all of the 4.0L engines from ’96 through 2000, except the ’96 Aerostar that should still use the FOTZ-A. There were a few Rangers built during these years that came without EGR, but they used the F3TZ-B cam, too. This approach looks good on paper, but you still need to know if the vehicle came with EGR from ’93-’95, and that’s not always predictable based on the year and application, so be sure to ask the customer before selling one of these engines.
Dealing with all of these different cams can be a problem, because there’s no absolute right answer short of rebuilding each engine exactly the way Ford built it, but that creates more applications and more opportunities to sell the wrong engine, so every rebuilder needs to consider the alternatives and do what works best for his shop and his customers. Consider this a disclaimer and make your own decisions based on the information available and your own experience.
1990-’94 All and ‘95-’96 Aerostar
1995-’97 Ranger, Explorer and ’97 Aerostar
All of these heads have the letter "A" cast into the head right above the right rear/left front exhaust port.
That’s the story on all the castings and the major components. Most of the differences are specific to given years or applications or both, so they can’t be consolidated or interchanged. The only exceptions are the rods that can be used in matched sets, no matter when they were made, the 90TM cranks with the notches that can be interchanged with the 90TM/96TM cranks with the long keyway as long as the matching crank gear is used, and the various cam consolidations that are open for discussion.
Rebuilders should not install an engine with the 95TM heads and deep-dish pistons in a ’95 or ’96 Aerostar. All of these engines had the same compression ratio whether they came with the original heads with the open chambers or the newer ones with the heart-shaped chambers, so they would seem to be interchangeable, but the computer calibration that was used for the old-style heads with the open chambers will not work with the newer heads with the fast-burn chambers. In fact, "It will burn the engine down in a few thousand miles," according to a Ford engineer who worked on this engine program. Ford continued to use the early heads on the ’95 and ‘96 Aerostar because they still came with the early calibration, so rebuilders must do the same.
Many of the heads that were produced for the 4.0L in ’89 and ’90 tended to crack around the spring pads on the intake side and had porosity problems down in the corners where the oil drained back into the valley. The cracks on the top can be found by Magnafluxing the heads, but the porosity problems won’t show up unless the head is pressure tested at about 70 psi. Some of the later heads have cracks around the oil drainback holes and quite a few are cracked in the chambers, so they should all be carefully inspected before being rebuilt. The threaded plugs on the top tend to leak, too, so they should be removed and reinstalled with sealer on the threads. Ford says they should be torqued to 80 ft.lbs after resealing them.
Rebuilders should also be aware that there are new aftermarket heads available from several different sources. Some shops have found that it’s cheaper to buy new ones than try to repair the used ones that have a lot of cracks.
All of these engines had four studded mains that were used to hold the windage tray in place under the crank. We recommend installing them in every engine in specific locations according to the diagram so the installer doesn’t end up moving them around and disturbing the torque on the main bolts in the process.
The two steel balls in the lifter valley that are used to plug the oil galleries must be removed in order to clean the block properly. They are almost impossible to remove from the top, but they can be driven out from the bottom by coming up through the oil holes in the mains.
The early crank gear has caused problems for many rebuilders. The crank gear was timed to the crankshaft by the small tab on the back of the gear that fit into the shallow notch that was machined in the step at the back of the snout. There is nothing to hold the gear in place against this step until the damper is installed, so it wants to slide forward and jump out of time during assembly, test and installation. Most rebuilders knurl the shaft or stake the gear in place to try to prevent the gear from moving, but that doesn’t always work, especially if the installer isn’t aware of the possible problem. Be sure to warn your assemblers and your customers so you don’t have to pay somebody to take it apart and do it over again.
Ford solved this timing problem in model year ’96 when they machined the crank and the gear for a full-length Woodruff key that indexed the gear on the crank and held it securely in place. Ford offers this revised gear (p/n F5TZ-6306-A), but it’s readily available in the aftermarket for a lot less money. The key can be a little hard to find because it’s a metric size; it’s available from Ford as well (p/n W702979S300).
The ‘90-’96 crankshafts can be interchanged as long as the matching crank gear is used, but always remember to stake the early gear in place in one way or another whenever using a 90TM crank with the short keyway and the notch in the step.
The roller lifters are held perpendicular to the cam by a steel pin in the side of the lifter that slides up and down in the groove that’s machined in the side of the lifter bore. Having this pin in the side of the lifter required a special design that had an inner and an outer body, so there’s some space in between them that can trap a lot of debris. That makes it very difficult to get them clean, so they’re hard to rebuild, and that’s a real problem, because new lifters are very expensive.
The rear seal on the 4.0L has always been prone to leakage. It appears that the original factory finish on the seal surface was too slick, so the seal just couldn’t control the oil. Ford offers a repair kit that comes with a sleeve and a seal (p/n F5TZ-6701-A), but it costs about $50 at the dealership. Rebuilders should definitely install a sleeve over the factory seal surface, but there are better alternatives in the aftermarket; Micro Sleeve (800-475-3383) and Classic (800-393-0544) both offer sleeves for the 4.0L cranks.
The pushrods and rockers on the 4.0L tend to show a lot of wear, even on engines with low miles. We suspect that there are two reasons for this problem: (1) The material in the rockers appears to be too soft, so they wear on the tip, and; (2) there’s not enough oil getting to the pushrod socket, so it gets worn out, too.
There’s pressurized oil at the rocker shaft to lubricate the rockers, but there’s no direct way for that oil to get to the pushrod sockets. There’s a passage in each rocker that allows oil from around the rocker shaft to migrate out to the small hole in the top of the pushrod socket, but it’s wide open on the outer end so there is no pressure there to feed the oil down into the socket.
Apparently the small hole in the pushrod socket that intersects this passage is supposed to meter oil down into the socket somehow, in spite of all the motion that’s trying to sling the oil out from the open end of the passage in the rocker. It’s hard to believe that any oil can actually get into the sockets, so it’s no wonder they wear out prematurely. Rebuilders should expect to rebuild or replace most of the rockers. The tips can be ground if they’re not worn too badly and the sockets can be repaired by installing a special insert that’s available along with the tooling needed from Silver Seal (800-521-2936) or Goodson (800-533-8010). Or, if you prefer to have someone do them for you, rebuilt rockers are available from Delta Camshaft at 253-383-4152.
You may want to consider flame-hardening the tips, too. Ed Davis at Waterhouse Motors in Tacoma, WA, has been doing this for awhile to eliminate wear on the tips. He found that the wear on the tips was loading the valves so hard to one side that they were wearing out the guides and causing other problems in the process.
Plan on buying a lot of new pushrods, too. Most of them are scuffed and worn on the tip due to the lack of oil in the socket.
That’s the story on the 4.0L. It’s pretty straightforward if you keep the castings straight and pay attention to the details. This has been a common engine in some of Ford’s most popular vehicles including the Ranger, Explorer and Aerostar, so there are over 3 million of them on the road and plenty of business waiting for the shops who know how to rebuild them and make them live.
You may e-mail Doug Anderson at firstname.lastname@example.org.