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Rebuilding the Ford 4.6L SOHC Engine
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19961999 Windsor "NPI"
The F65E/F75 and F75E castings were all used on the Windsors from 1996 through ’99. They had individual caps on each cam journal, 12 bolts instead of nine around the perimeter of the head for the cam cover, and the four bolt holes on both ends were 10 x 1.50 mm instead of 8 x 1.25 mm like they were on all the Romeo heads.
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 "power improved" (PI) casting (XL3E) with the square intake ports was introduced in 1999. It has bigger intake valves, different springs, and a small, heart-shaped chamber that has a swirl-fin behind the intake valve. These heads don’t have the "restrictor" that’s driven into the head, so the wide cap has the small slot machined in the divider between the two sides.
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.
Even though we’re not talking about anything beyond 1999, you should be aware that there is a Romeo "PI" casting out there, too. The 1L2E casting has ladder caps, small bolt holes in both ends and nine bolt holes for the cam cover along with the square intake ports and the small heart-shaped chambers.
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.
There have been four different timing sets used on the modular motors, three on the Romeos and one on the Windsors.
The original timing set used on the Romeo motors had a roller chain, steel-backed, plastic guides and the thin (about .960˝) tensioners along with right and left tensioner arms. There were right and left tensioners with different oil passages on the back side, but they were easy to tell apart because they had either an "R" or "L" cast right on them.
1992-1/2 -1993 Romeo
The second Romeo timing set still used the roller chain and it looked the same, but it was slightly different because the mounting pad on the head was 1.0 mm/.040˝ shorter than it was on the earlier castings, so the tensioner was thicker and there were right and left tensioner arms. There were three tensioners used on these engines a right one (marked “R”), a left one (marked “L”), and a universal design with no marking on it.
The third timing set for the Romeo motors had a link-style, silent timing chain instead of the roller chain, so it had different sprockets, but everything else stayed the same.
The tensioners and pivot arms on the Windsors are the same ones that were used on the later Romeo engines, but the guides are made of plastic with no steel backing and some of the mounting holes were moved, so they’re completely different. All the Windsors had the link-type, silent timing chain and gears.
The cams for the 4.6L engines can be pretty confusing. They’re all hollow designs with pressed-on lobes, but that’s where the similarity ends, because there are right and left cams that came with and without the gears and there are several different profiles to consider.
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.
There have been several front covers used on these engines, depending on both the year and the application. The chart (below) provides a good overview, but there are a few things worth noting:
1990 to 1992-1/2 Romeo
The F1AE/F2AE front covers had 15 small holes (8.0 mm) around the perimeter and no bosses for the tensioner.
1992-1/2 to 1995 Romeo
The F3AE/F5AE covers still had the small (8.0 mm) holes, but they also had six cast bosses on the passenger side that were used to mount the tensioner and idler for the serpentine belt.
1996-1999 Romeo and Windsor Car (except 1999 Mustang)
The front cover for the car was changed in 1996 when the Windsor motor was introduced. The six bosses for the tensioner were the same, but the bolt hole by the water pump was moved up about .250˝ and 10 of the holes were opened up to 10.0 mm to accommodate the larger bolts that were used for some of the holes on the Windsors.
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)
All of the trucks, Expeditions and vans (except the 1999 Econoline) shared a common front cover. The F65E casting had 10 large 10.0 mm bolt holes and five, small 8.0 mm holes along with six bolt bosses for the tensioner. However, the bosses for the tensioner were arranged in a different pattern that was unique to the trucks, so the car and truck covers can’t be interchanged.
The front cover on the 1999 Mustang was an XR3E casting. It had four bosses for the tensioner and a machined pad for the idler further down on the passenger side of the cover.
The 1999 Econoline had its own special 2L3E front cover. It looked the same as the earlier F65E truck casting, but the 30° timing pointer was no longer cast on the cover.
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.
- Ford recommends torque-plate honing all the 4.6L blocks.
- Ford recommends replacing the head bolts every time the heads are removed from the engine.
- There is no way to know whether a Windsor motor came with a six-bolt or eight-bolt crank until it’s out of the vehicle, no matter what the customer says, so make him take it out and look at it before you ship him an engine.
- These blocks can’t be bored more than +.020˝ (oversize) because the fire ring in the head gasket is too small to accommodate a larger bore.
- Don’t mix up the ring sets. Putting a deep top ring in a shallow groove or vice versa is a sure-fire comeback.
- The 4.6L Ford was the first engine to use a multi-layered steel head gasket. It required a super-slick finish on the heads and block. We have been successful rebuilding this engine by maintaining a surface finish around 40 Ra on the block and 20 Ra on the heads. Don’t take chances with a finish that’s too rough. The geometry of the head and block must be straight and true as well in order to achieve proper sealing.
- You can’t recondition the rods by cutting the caps because of the cracked cap, but there are oversize rod bearings available in the aftermarket that work fine.
- We have seen several of the left hand cam sprockets for the Romeo motors that have the tab that indexes in the keyway completely sheared off. Check both the cams and the gears carefully before reusing them.
- There are reports that there were some oversize rods in new engines, so double-check them, especially if you’re not using oversize rod bearings.
- These engines appear to be very prone to detonation. We have seen several pistons with rod bearings that have been pounded to death from abnormal combustion. Some of the Romeo engines that are used in police cars and limos appear to have serious detonation problems, so watch out for comebacks with these applications.
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.
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