Engine Types

There are 6 different displacements available, 3.9L, 4.6L, 5.0L, 5.4L, and 6.8L. The 4.6L, 5.4L are available in single and double overhead cam versions. The 3.9L DOHC engine is installed in the 2002 up Thunderbird. The 5.0L is also a DOHC engine but is only available through Ford Racing as a crate
engine sometime in 2004, it has never been installed in a production vehicle. The 6.8L is a V-10. The vehicles these engines can be found in are as follows:

VIN Y for the Mustang Cobra refers to the 2003 DOHC supercharged model.
VIN 3 for the Ford trucks refers to the supercharged SOHC Lightning engine.
VIN 6 refers to 4.6L SOHC Windsor produced engines.
VIN W refers to 4.6L SOHC Romeo produced engines.
VIN X refers to 4.6L SOHC Windsor produced Mustang engines.

The numbers & letters above are the 8th digit of the VIN

The Lincoln Mark series are probably the most popular 4.6L DOHC engines, due to the relatively low
price compared to the Cobra engines. What are the differences between these two engine's? Following
are some, but not all of the differences.

The Cobra comes with a forged steel crank using 8 flywheel bolts, the Lincoln comes with a nodular cast iron crank with 6 flywheel bolts.
The Lincoln uses a different oil pan with a reservoir on the side.
The oil filter/water outlet castings are different.
The Intake cams on the Lincoln are a slightly different profile.
The Intake on the Lincoln is different from the one used on the Cobra, although they do use the same cylinder heads and a Cobra intake will bolt on.

The 6.8L V-10 has never been cast in aluminum except for a limited number that Ford did for a Mustang concept vehicle. The 5.4L DOHC has been cast aluminum but has, up to now, only been available in the supercharged GT40. We will have to wait and see if Ford offers this block through it's performance parts division. Just a guess, but you probably won't find many of these at your local pick-a-part yards.

What's a Triton? This refers to Ford truck engines.

What's an Intech? This refers to Lincoln engines.

Crankshafts

DOHC & SOHC Cranks will interchange. Some blocks may require minor block modifications for counter weight clearance when installing a forged crank in a block that previously contained a cast crank. The
most common cranks for 4.6L engines are the nodular cast iron units. They come in both 6 & 8 bolt flywheel configurations. Note that just because a crank has 8 bolts does not mean that it is forged. The
2-valve Windsor engines use both a 6 & 8 bolt flywheel, the Romeo engines use 6. The only factory forged cranks available for the 4.6L DOHC engines are installed in the Cobra. These cranks are manufactured by Gertach in Germany for Ford. Ford Racing Performance Parts (FRPP) offers these cranks for sale under part # M-6303-D46 for 425.00. The correct 8-bolt flywheel for this crank is sold under part # M-6375-G46
for 250.00. This is a billet steel flywheel.
The cranks in the 5.4L DOHC and SOHC engines are also available in cast or forged. Most of the cranks are forged, but not all. The only way to know for certain is to look at the parting line. Thick line for forged, thin line for cast.
All 6.8L V10 engines have forged crankshafts.

Connecting Rods

With the exception of the 2000 Cobra R (Carillo) and the 2003-2004 Cobra's (Manley H-beam), all modular engines have come with sinter forged powdered metal connecting rods. There has been a lot written about these much maligned rods. The truth is, they are fine for use in mild performance applications. If a blower, nitrous or turbo is in your future, you would be doing yourself a favor by upgrading your rods to forged steel like Manley's H-beam rods.
There are several versions of the factory rods. The Windsor engines use full floating pins where the Romeo based engines use pressed pins. The 4.6L SOHC passenger car engines have the weakest rods, the Windsor (or Triton) engines use a larger connecting rod that is stronger than the passenger car engines. The 4.6L DOHC engines use the same rods as are used in the Windsor's. The strongest factory style rods to date are the rods used in the supercharged 5.4L lightning. These rods have a larger big end than the standard modular rods.
4.6L Rod length = 5.93"
5.4L Rod length = 6.65"

Pistons

The pistons used in modular engines are all of the hypereutectic style, with a few exceptions. These exceptions are the supercharged Lightning and Cobra. This should tell you something about the durability
of the factory pistons. If Ford decided (at considerable expense) that it was necessary to upgrade to forged pistons for forced induction maybe you should heed their advice. We have seen forced induction cars run
on factory pistons and produce good horsepower, the question is, for how long? If you are building a forced induction engine you need to understand that the factory pistons do have their limitations and when you reach these limitations, it's not pretty.
When building a modular engine for mild performance applications, the stock pistons will hold up fine.
Most of the pistons used in modular engines are dished. Pistons are interchangeable between the DOHC and SOHC, 6.8L, 5.4L & 4.6L engines. Obviously, you will need to check piston to valve clearance. Following are the dish volumes used in these engines:

SOHC 4.6L, 5.4L,and 6.8L
1991 thru 1998 ------- 10.49cc dish
1999 thru 2000 ------- 18.10cc dish
2001 thru 2004 ------- 15.80cc dish

DOHC 4.6L
1993 thru 1998 ------- 2.66cc dish
1999 thru 2002 ------- 4.54cc dish

DOHC 5.4L
1998 thru 2004 ------ Flattop

Cylinder Heads

SOHC
The most in depth evaluation of sohc cylinder heads can be found at the previously mentioned link http://www.babcox.com/editorial/ar/eb40228.htm
For performance applications the choice is more clear. These heads can be separated into pre-1999 non-performance improved (NPI) and post 1999 performance improved (PI). If you have a set of pre-1999 heads and want to use them, understand that a fully ported set of these heads will perform a little better than a
set of PI heads out of the box. There are good reasons for using the early heads, mainly cost. To convert
to the PI heads on a non PI head engine will require not only new heads but intake and associated
hardware as well. If your willing and capable of doing your own porting work you can build a strong SOHC engine with these heads, just understand that these heads will never perform as well as a set of ported PI heads. Be very careful when porting these heads. There is not much material to play with. This applies to
all castings.
The post 1999 heads (PI) are excellent castings. These heads work well as is, but really respond to a
good port & polish job. After porting these heads can flow as well as the FRPP heads listed below. For supercharged applications or hi-performance engines these heads are a good starting point. The moral of the story is: if you are looking to buy an engine, buy a 1999 or newer.
There is one other option, the FRPP hi-performance heads for the early (1996-1998) engines. These are probably the best heads available for the SOHC 4.6L engines. They also respond well to a good port & polish job. These heads have never been offered on a production vehicle but they can be ordered through FRPP under part # M-6049-D46. Be sure to shop around before purchasing these heads. Prices vary from vendor to vendor but expect to pay about 800.00 each without cams. Ouch!

The numbers listed below are for reference only. Your results will vary depending on who does your
cylinder heads and whether or not they were drinking beer at the time. These are not our flow numbers
so take them with a grain of salt.

Everything stated above regarding the 4.6L cylinder heads applies to the 5.4L and 6.8L V-10. The
difference being, the 5.4L and 6.8L V-10 did not receive the PI heads until year 2000.

After looking at the cylinder head combustion chamber volume and the varying amount of dish in the
factory pistons it's easy to see that changing heads and pistons from different years will result in a compression increase or decrease. The following chart will give you a guide when scrounging the junk
yards for engines. Your compression ratio will vary depending on combustion chamber work, head gasket thickness, decking of the block, & milling of the heads.