Rebuilding the Ford 4.6L SOHC Engineby Doug Anderson
The 4.6L Romeo SOHC was introduced in 1991 as the first born in an all new family of engines for Ford. It had a rigid, deep-skirted block with cross-bolted mains, long rods that gave it a favorable rod length-to-stroke ratio, a lightweight crank and pistons, and SOHC aluminum heads that incorporated all the latest engineering theory with ports and chambers that were designed to make more power with fewer emissions.
The 4.6L was lower, shorter and lighter than the 302, but the base engine made more power than the 302, got better fuel economy and passed all the emission tests without a thermactor pump. Ford called it its "modular" engine because it was part of a whole new family of engines that were intended to have a common architecture "so they could share similar production tooling and have many interchangeable parts."
The V6 that was originally intended to be part of the modular program never did get built, but there are several engines in the V8 family, including one 4.6L DOHC and two SOHC motors, along with the 5.4L V8 and the 6.8L V10 that are all part of this "modular" family.
Although the idea of a standardized, modular engine looked good on paper, it hasn’t worked out quite as well in the real world, because there have been many changes that have created lots of variations over the last 10 years.
The 4.6L engines built in the Windsor plant are completely different than the ones built in the Romeo plant, and there are significant differences in the engines that have been built in each plant from year-to-year, so there are at least eight short blocks, seven heads and 13 long blocks so far, not counting the CNG and DOHC engines.
It’s pretty confusing to keep track of all the different combinations, so nobody seems to know what goes where or exactly when it was used. We tried to get some help from Ford, but we were unable to find anyone who was willing to share any information, so everything in this article is based solely on what we have seen and pieced together along with the help of some other people in the industry.
We believe that what we have figured out so far is pretty accurate, but we know there’s more to the story because we learn something new on a regular basis, so start with what’s here and build on it with your own experience.
With that disclaimer in mind, let’s take a look at the 4.6L SOHC modular engine and walk it through, year-by-year, beginning with the blocks, and see what Ford has done with these engines from 1991 through 1999, keeping in mind that the CNG and DOHC applications aren’t included in this discussion.
1991 – 1992 Romeo
1992 – 1995 Romeo
The corner of the block is reinforced by a triangular web that is parallel to the pan rail and perpendicular to the front of the bell housing, too. And, these blocks still have only four cross-bolted mains instead of five like all the later Romeo blocks.
1996 – 1998 Romeo Car
The freeze plug on the driver’s side was moved up closer to the deck and the bolt for the front cover that’s right beside the big hole for the water pump was moved up about .250˝ closer to the deck, so it’s located at 2 o’clock instead of 3 o’clock when facing the block (see photo below).
These blocks appear to have been used for the 1996 and ’97 cars (the "V" in the casting number indicates that the casting was originally designed for a Lincoln) and the 1997 pickups that were built in 1996 and titled as ’97s (the "5" in the casting number indicates that it was intended for the pickups).
This block will work in all of the RWD cars including the Fords, Lincolns and Mercurys, and in some of the trucks, too, but it won’t work in all of the trucks because it doesn’t have the extra bolt hole between the second and third soft plug on the driver’s side that’s used for the oil cooler that was included with the optional trailer towing package on the trucks.
By the way, there are some Crown Victorias with the Police Interceptor package that have an oil cooler, too, but it’s mounted under the radiator, so this block should fit all the cars up through 1998 or ’99.
1997 – 1999 Romeo Trucks, Vans, Expeditions and 1999 Cars
Both of these castings, the F7AE and XW7E, have a second bolt hole under the existing one between the second and third soft plug on the driver’s side. Both of these holes were used to mount the extended housing that moved the oil filter to the back, closer to the bell housing, so there was enough room for the oil cooler that was part of the optional trailer-tow package on the trucks and Expeditions.
Since most of them came without the trailer-tow package, and it seems unlikely that Ford would have had the same engine with two different castings waiting on the assembly line, we believe that the F7AE block was used in most of the pickups, vans and Expeditions through 1998 until it was replaced by the XW7E casting in 1999.
1996 – 1999 Windsor
All five main caps on the Windsors are crossbolted, but they have dowels between main caps and block instead of the jackscrews that were used for the Romeo blocks. All of the Windsor blocks have the second hole on the driver’s side for the extended housing that moved the filter to the back of the engine and they all have a threaded boss in the valley that was used for the knock sensor or a bracket, but the hole may be either 8.0 mm or 12.0 mm, depending on the year.
All of the F65E-BB blocks and some of the F75E blocks had a 12.0 mm hole, but some of the F75E castings had the smaller 8.0 mm hole. The parts book says that most of the trucks had a knock sensor in 1997 and ’98, so they needed the bigger hole, but some applications came without it and used a special stud and nut to hold the water pipe that laid in the valley. We have seen a F75E block with PI (Power Improved) heads on it with an 8.0 mm hole, so we know that the hole size was changed by 1999. However, it could have been changed earlier, too, but our best guess is that the 1997s and ’98s had the 12.0 mm hole and the 1999s had the 8.0 mm hole.
The bolt pattern for the front cover is the same as it is on the late Romeo blocks, but the two bolt holes just above the pan rail are 10 x 1.50 mm instead of 8 x 1.25 mm.
Most of the Windsor blocks we have seen have the letter "W" cast somewhere on the block, on the front, on the back, in the valley, and sometimes even on the sides, too, so they’re usually pretty easy to spot.
1991 – 1995 Romeo
1996 – 1999 Romeo
1997 – 1999 Windsor
It appears that most of the Windsors used the eight-bolt crank, but there are definitely some of them out there with six-bolt cranks, so check with the customer before selling an engine or a crank.
All of the Windsor engines that have the six-bolt crank must be built with the F65E casting that has the narrow front counterweight because there are two machined pads on the back side of the front main that stick out far enough to hit the thick counterweight on the F1AE crank.
None of these connecting rods come with any casting numbers, but you can sometimes make out the identification numbers that were printed on the shank of the connecting rods; we have seen F1AE and F2AE numbers, but there are probably several others that we haven’t noticed.
1996–1999 Windsor With NPI Heads
1999 Windsor with PI Heads
It has two "ladder style" cam caps, nine bolt holes for the rocker cover and it’s threaded for long reach spark plugs most of the time. However, there are some F1AE castings that are threaded for the later short reach plugs, so be sure to check the threads before using this casting.
1992-1995 Romeo (1992-’94 all, 1995 T-Bird/Cougar)
1995–1997 Romeo Car (1995 Crown Victoria, Mercury Marquis, Lincoln Town Car and 1996–1997 all)
These heads could be converted for use on the trucks by drilling and tapping the blind hole and spot facing the boss for the sensor, but it takes a milling machine and a fair amount of time to do it right, so it’s probably easier to catalog them separately and use the castings that aren’t drilled on the cars that came without the sensor.
1996–1999 Romeo Truck and 1998–1999 Romeo Car
1996–1999 Windsor "NPI"
The combustion chambers on these heads had the "swirl-fin" behind the intake valves and they had small, oval intake ports, so they’re called "not power improved" (NPI) heads to differentiate them from the later design that’s known as the "power improved" (PI) head. The "NPI" heads were used on all Windsors up through 1998 and for some applications in 1999, so be sure to verify the casting number before deciding which one to install on one of these later engines.
Most of the F65E/F75/F75E castings have a small, round, machined "restrictor" driven into the head right under the wide cam cap, but we have seen a F65E with a machined slot in the cap and no "restrictor" in the head. The hole in the heads that have the slotted cap is too small for the "restrictor," so it’s not a problem as long as you know what you’re looking for and you make sure you install the "restrictor" in the heads that came with it.
Rebuilders may have one problem with the "NPI" Windsor heads; the two blind holes that are used for the pegs that hold the intake gasket in place during assembly are on the bottom (toward the valley-side) of the intake ports most of the time. But, there are some F75E castings that have the holes at the top side of the ports (near the head). They were on the bottom on the F75E casting when it was used on the 4.6L from 1996-’99 and on the 5.4L in 1997.
They were on the top of the F75E castings when they were used on the 5.4Ls in 1998 and ’99, and they’re on the top of all the service replacement heads that are sold now. Rebuilders need to send the matching intake set with a Windsor engine when they sell one with "NPI" heads.
1999 Windsor "PI" Heads
The "PI" heads weren’t installed on everything in 1999, and the parts books aren’t clear about exactly where they were used, so there’s a lot of confusion about which applications came with or without them.
In fact, no one seems to know anything for sure, except that: 1) all the Mustangs had "PI" heads in 1999; and 2) some of the trucks and Expeditions had them in 1999. Our best guess is that all the Expeditions got them, along with some of the F250 pickups, but they definitely weren’t used on all of the pickups in 1999, so be sure to ask for the casting number before you sell an engine or a head.
This casting number is for a 2001 Explorer, so the "PI" head probably wasn’t used on Romeo engines until then. But, it’s possible that there were some earlier applications in spite of the casting number, so keep an eye out for them when you get a late model Romeo core.
1992-1/2 -1993 Romeo
The cam chart (below) is our best take on it with the help of Milt Olson from Engine Power Components. We’ve also seen three other cams that we haven’t been able to identify by application (F1AE-6250-BD/F65E-6250-AA/F1AE-6A274-BD), so we aren’t using them in anything at this point. The rest of them appear to be interchangeable as shown on the chart, but that’s just an opinion, so let your conscience be your guide when consolidating cams for these engines.
1990 to 1992-1/2 Romeo
1992-1/2 to 1995 Romeo
1996-1999 Romeo and Windsor Car (except 1999 Mustang)
The F6AE/F7AE/F7ZE/F8ZE castings were used on all the cars from 1996 through ’99, except for the Mustang that had its own unique front cover in 1999.
1996 – ’99 Truck, Van and Expedition (except ’99 Econoline)
That pretty well covers all the major components for the 4.6L Ford engines, but that’s not all there is to the story. There are a few other things every professional rebuilder should know about these engines before starting to rebuild them.
That’s what we know about the 4.6L Ford. Start here and build on this information with your own experience and you’ll be ahead of the game. There are thousands of these engines out there and they’re not all going the miles, so there should be plenty of opportunities for everyone in the industry to build a bunch of them.
Editor’s Note: This article would not have been possible without the help of many other people in the industry who shared their knowledge and experience. A special thanks to Roy Berndt at the Production Engine Remanufacturers Association (PERA), Milt Olson from Engine Power Components and the people at Mahle for all their help.
Doug Anderson is vice president of Grooms Engines, Parts, Machining, Inc., a production engine remanufacturer in Nashville, TN.