In Part 1 of this story we introduced you to Ford's new-generation overhead cam Modular V-8 engines first introduced in 1991 in the Lincoln Town Car. We showed you the differences between Modular V-8 engines by explaining the variations between the Romeo, Michigan, and the Windsor, Ontario, engine plants. The differences are significant from one plant to the other, which affects interchangeability. This month, we're going to introduce you to Modular V-8 cylinder heads and their respective differences in our quest to teach you more about Ford's newest V-8 engine.
Choosing the right cylinder head for your SOHC or DOHC Modular V-8 boils down to understanding the differences between the two plants, and the pivotal year for performance: 1999. Ford improved the Modular V-8's cylinder heads that year on both the SOHC and DOHC engines.
SOHC Engines
It gets complicated when we get into cylinder heads for the 4.6L SOHC engines. To keep it simple, we will tell you there are two basic cylinder head designs: the Power Improved head casting from 1999-and-up and the dated round-port head from 1998-and-back. Ford calls it the non-PI head. We wish it were this simple in the real world of Modular V-8s, but it is a lot more involved in terms of interchangeability and design.
The '91-'92 Romeo SOHC head sports an F1AE casting number, with a bridge-style camshaft support bridge across the cam journals. These heads have no cam bearings. The camshafts ride right on the aluminum saddles (journals) in a cushion of engine oil under pressure. The cam covers sport nine bolt holes. There are two types of spark plug holes: short-reach and long-reach. Long-reach spark plugs indicate early castings. Later castings have a shorter-reach spark plug. This is important to remember whenever you're swapping heads.
The '93-'95 Romeo head castings have F2AE and F4AE casting numbers. All have short-reach spark plugs like later F1AE castings. Based on castings we have seen, provisions for the timing chain tensioner change on the '93-'95 head. So be mindful of this fact when you are swapping cylinder heads. In 1995, Ford changed the Romeo SOHC head castings again with a new casting number--F5AE--with a revised high-swirl combustion chamber. This casting would remain virtually the same until 1999, replaced by the PI head. Early castings had 51cc chambers with 146cc intake ports. These ports flow 156 cfm at .500-inch lift. This is not a performance head.
This is the Power Improved SOHC cylinder head Ford began using in 1999. Shown here is the Romeo PI head for the SOHC engine. Note the cam journal bridging, which is common with the Romeo head. | 
"Power Improved" comes from the teardrop intake ports, round exhaust ports... | 
...and heart-shaped chambers. Timing cover bolt holes on the Romeo head are 8 mm. |
When the Windsor foundry and engine plant came on line in 1996, so did a new crop of SOHC head castings designated primarily for trucks and large sport utilities. These castings are identified by F65E, F75, and F75E casting numbers until 1999. Cam covers are easily identified by 12 bolt holes instead of 9. Timing chain cover bolt-holes are also different on the Windsor heads--larger than the Romeo's. This means you have to stick with a Windsor timing cover when you are using Windsor heads. Again, Windsor everything, Romeo everything for simplicity and compatibility. The Windsor head has a high-swirl chamber like the F5AE Romeo head.
Beginning in 1999, Ford went to the Power Improved head at both Romeo and Windsor with the differences we have already addressed between the two plants. Look for a casting number of XL3E on this one, along with teardrop intake ports and heart-like 42cc combustion chambers. Intake port volume is 152 cc, flowing even more air at .500-inch valve lift. These heads are good for about 30 more horsepower if everything else is in place.
The Windsor PI head has separate cam journal caps. The Romeo PI head has the bridge-style caps mentioned earlier. This makes them easily identifiable at a glance. The Romeo head is the 1L2E casting. Timing chain cover bolt holes on the Romeo head are smaller (8 mm) than those we see on the Windsor heads (10 mm).
Ford Racing Performance Parts introduced a high-performance SOHC head in 1998. According to Sean Hyland of Sean Hyland Motorsport and author of How to Build Max-Performance 4.6 Liter Ford Engines (SA Designs PN SA82) , it's the best SOHC head produced to date. It has 51cc chambers, 173cc intake ports, and 206 cfm at .500-inch lift. The downside to the FRPP head is incompatibility with '99-and-up SOHC induction systems. It does, however, work well with '98-and-back induction systems.