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Rebuilding The Ford 4.0L Pushrod V6

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.

By Doug Anderson

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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.

BLOCKS
There have been three blocks used for the 4.0L. Each one is unique in some way, so none of them can be interchanged.

1990-’94
The first 4.0L block was a 90TM-AB casting. It had six bolt holes on the passenger side and 10 bolt holes on the driver’s side. The dipstick hole measured about 0.380˝ in diameter.

1995-’96
The original block was changed in ’95. The new 95TM-AB casting had two more bolt holes on the passenger side and two more on the driver’s side for a total of eight on the right and 12 on the left (see photos above). The dipstick hole remained the same at 0.380˝.

1997-2000
The block was redesigned again in ’97 to reduce noise, vibration and harshness (NVH). Both of the pan rails on the 97TM-AA casting were wider and there were two more gussets added between the pan rail and the horizontal rib that’s right above it on the passenger side. The dipstick hole on this block was enlarged to about 0.435˝, too.

CRANKS
Ford has used four different cranks with five different casting numbers in the 4.0L. In ’95, the angled slot that was machined in the step at the back of the snout was increased in length. In ’96, the crank came with a full-length keyway and it had another step machined into the raised area at the back of the snout. In ’97, the flange for the flywheel was changed from a six-bolt to an eight-bolt pattern. And, in ’99 the specifications for the bobweights were changed.

1990-’95 and ’96
The original crank casting was the 90TM-AB. It was used up through ’95 in some applications, but it was replaced by the 90TM-AA in most of the ’95s. These cranks are easy to spot because they have "4.0" cast in the outer edge of the second counterweight. They both had a six-bolt flange for the flywheel and a short, angled notch machined in the step at the back of the snout, but there was a subtle difference in the length of the notch, depending on the casting. The notch in the original 90TM-AB shaft was 0.420˝ long while the slot in the later 90TM-AA casting was 0.673˝ long. This change occurred sometime during model year ’95, but the big change came even later in the year when the snout was machined for a full-length Woodruff key and a second step was added for an another gear.

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.

1997-’98
The crank was revised again in ’97. The new 97JM-AC casting came with an additional step, the long keyway and an eight-bolt flange for the flywheel. This was the same casting that was used in the SOHC 4.0L for ’97 and ’98, so the cranks from both engines can be interchanged, in spite of the fact that Ford gave them different part numbers.

1999-2000
The XL2E-BA casting that was introduced in ’99 was used up through 2000 when the OHV engine was discontinued. This crank appears to be the same as the 97JM-AC, but there’s a noticeable difference in the bobweights. The 97JM had 880 grams on all the bobweights while the XL2E used 850 grams for cylinders 1, 2 and 3 and 842 grams for 4, 5, and 6, so there’s an overall difference of 4.3%. Installing the light crank in a ’97 engine with the heavy pistons will overbalance the assembly and add to the vertical imbalance that makes the steering wheel shake, so don’t use this light crank in an engine with heavy pistons.