difference in 2001 cobra heads?

[FirstOnRaceDay.]

I just purchased a pair of ported 2001 Cobra heads. I will be putting a set of B head cams in them, getting the spark plug thread extensions and the cooling flow through mod but what else needs to be done? I have an eaton swap in mind with forged rotating assembly. Is there another route i should take? i do have a budget in mind but my engine builder won't charge me much more to rebuild the whole thing vs just putting new heads on it. So pretty much whatever i want done to it will be about $2k-2500 aside for the parts i show up with. stock or ported eatons are only a few hundred dollars now so it seams reasonable. i know there are lots of little parts but i don't mind part hunting for good prices. i have already payed for the C heads so i am commited to at least that extent so that's my starting point. where do i go now? i have also been told i can not use 96 a/c with an eaton swap, is this true? i believe this would be the absolute best site to ask these questions with the knowledge here but if there is another place i should be directed to please let me know.



(can't get much direct info from the sn95 cobra section)

 

[Jimmysidecarr]

So you are converting your 96 to as close to Terminator 03/04 powered as possible, except with a nice and light Teksid block.... correct?

If those heads were professionally done then they are probably very close or better than 03/04 heads, but not better than PORTED 03/04 heads.
Glad to hear that you know to fix the spark plug threads issue.
Sounds like a nice build.

Make sure the pistons are compatible with C head valve clearance, not sure if they are different but you will want to know before it is too late.

Using close to 9 to one comp ratio will allow more power at less boost and IMHO is a good idea.

Also make sure your support is up to the task.
Air monitoring, fuel delivery, cooling and cooling air flow that stuff does matter.

 

[GodStang]

B/Swirl Port: (93-97 Lincoln Mark VIII, pre 99 Lincoln Continental, 96-98 Cobra).
The first and only production Ford head with two (square primary, round secondary) intake ports per cylinder, these swirl port castings arrived first in the ’93 Lincoln Mark VIII. Aptly named, due to the way they promoted the incoming air to swirl into the combustion chambers, much like water running down the drain of a once full sink.

Through the years these heads have proven themselves to be excellent high rpm (8000rpm+) performers—mainly in power adder applications--since their tremendous combined intake port cross sectional area and volume (when combined, a full 55cc more than any other 4.6L head design) provide for exceptional power production in the upper regions of the tach. Ironically, it’s those same big, beautiful, twin ports that also prove to be the B head’s largest inherent design flaw. The extra intake port size has a tendency to kill low/mid rpm intake port velocity and power production—hence the use of Ford’s first IMRC (intake manifold runner control) intake on the 96-98 Cobra. By allowing air to reach only one of a B head’s twin intake valves, velocity, and therefore low/mid range torque production was restored in situations under 3250rpm. Later head designs are clearly superior in this regard, which happens to be the one of the most important considerations for those wanting a stout street motor.

There is also some controversy over the single fuel injector/dual intake port setup. Some claim insufficient air/fuel mixing because of the compromised design, however, others contest that the ability to make 1000+rwhp with only minor porting and some form of power adder is testament to the contrary. Whoever you believe, there is little doubt that even after as little as 8,000 miles, carbon and other deposits tend to form on the secondary ports, causing a major airflow impedance, as there is no fuel present to clean them. B heads feature a somewhat small stock exhaust port that really hinders flow in power adder applications. Major gains from porting come with a quality valve job, some pocket and lots of exhaust work. There really isn’t a lot of material to remove from the intake ports themselves.

The Bottom Line: B heads aren’t the best choice for a naturally aspirated street motor. In order to really shine, they need to be paired with a power adder and a short block that can sustain high horsepower and rpm levels. These, the oldest heads, may still be a great choice for full race applications.

Stock Intake Choices: ‘93-‘97 Lincoln Mark VIII, ‘96-‘98 Cobra.
Aftermarket/Modified Stock Intake Choices: HCI, SSR, PHP.
B head dimensions: Combustion Chamber: 52cc, Intake Port Vol.: 107cc primary (square), 115cc secondary (round). Intake Port Entrance: 1.500x1.300” primary (square), 1.660x1.400” secondary (round), Valves: 37mm Int., 30mm Exh.

C/Tumble Port: (99/01 Cobra, 99 Lincoln Continental).
These second-generation Ford DOHC heads feature a single intake port per cylinder with a smaller cross sectional area that boosts incoming airflow velocity compared to previous years. To understand how C heads earn their “tumble port” designation, try to imagine an Olympic high diver doing repetitive front somersaults before cleanly entering a pool at the bottom. This controlled tumble allows for better air/fuel mixing than in the earlier swirl port heads. The new port design allowed for both substantial increases in midrange torque, and superior horsepower production under 8000rpm when compared with earlier heads. Combustion chamber size is also up 2cc.

The design downfall of C heads, and their larger (5.4L Navigator) cousins, is the relatively flat floor and utter lack of a short turn radius in the throat of the intake port. As such, the incoming air tends to overshoot the valves, making the port think the valves are smaller than they actually are. Some ‘99/’01 Cobra owners reported a “ticking/pinging” noise coming from the drivers side head of their cars. This is due to insufficient cooling around the #6, 7, and 8 cylinders that allowed the valves to overheat and therefore seat improperly. Ford remedied the situation by issuing a TSB to remove and replace the affected heads with a version that featured altered coolant flow.

C heads feature a small exhaust port much like Ford’s earlier swirl port heads, but unlike in B heads, both the intake (throat region) and exhaust ports can see extensive porting work. However, removing too much material from the intake port (mouth region) of a tumble port head will kill velocity very quickly, so make sure your head porter knows what they are doing!

The Bottom Line: C heads remain a viable performance upgrade for those looking for more punch in their street driven 4.6L four valve, without having to pay new part prices for the ’03 DOHC or FR500 versions. The increased midrange torque production and greater overall area under the power curve (when compared to swirl port heads) will enhance the performance of a street/strip driven (8,000rpm and under) modular regardless of application.

Stock Intake Choices: ‘99/’01 Cobra, ‘03/’04 Mach 1 & Aviator, ’03 Marauder, FR500.
Aftermarket/Modified Stock Intake Choices: Al Papitto short runner/ported ‘99/’01 Cobra, Sullivan, Aviator, '03/'04 Mach 1
C head dimensions: Combustion Chamber: 54cc, Intake Port Vol.: 177cc, Intake Port Entrance: 1.960”x1.350”, Valves: 37mm Int., 30mm Exh.

Navigator: (98+ Lincoln Navigator)
These 5.4L DOHC heads feature essentially the same intake port design as C heads, however they have a much larger intake port volume than 4.6L castings. Despite the fact these heads feature a relatively small exhaust port, the extra intake port volume could be very beneficial in helping fill a motor of greater displacement—think 5.4L. Expect slightly better midrange torque, and sub 8000rpm horsepower production than even C heads, however the larger intake port size leaves a slim selection of intakes to choose from when utilized on a 4.6L block. Forced induction fans take note, Navigator exhaust ports feature a thicker exhaust divider (while keeping the same overall exhaust port size as B,C, and FR500 heads) that allows coolant to circulate through this vital area. Conversely however, the larger divider can also hurt flow by utilizing additional space in the port.

The real downside to Navigator heads, when used on a 4.6L based motor, is the severe limitation they impose on intake selection. The physically larger 5.4L heads don’t leave a lot of room (when installed on a 4.6L block) between them for an intake plenum to sit—though they do bolt right up. Remember that since Navigator intake ports are essentially clones of those of C heads (just on a larger scale), they too suffer from the same intake port flaws that plague the earlier tumble port design--no short turn or floor in the throat of the intake port.

The Bottom Line: The extra port volume the Navi’s possess could be very beneficial in filling a motor with greater than 281 cubic inches of displacement, or in high rpm N/A street/strip or boosted combinations. Fans of boost should remember the cooled exhaust port divider. Lack of intake availability is the real downfall of this otherwise wonderful casting.

Stock Intake Choices: None (4.6L), 98+ Navigator (5.4L)
Aftermarket/Modified Stock Intake Choices: Al Papitto short runner 99 Cobra (4.6L), sheet metal
Navigator head dimensions: Combustion Chamber: 53cc, Intake Port Vol.: 184cc, Intake Port Entrance: 2.290”x1.400”, Valves: 37mm Int., 30mm Exh.

’00 Cobra R: (’00 Cobra R and now Ford GT/GT500 with .020" raised intake ports, unique adjusters, and better casting quality throughout)

Cobra R heads are bar none the best Modular heads available today. However, their extremely scare supply makes them both ridiculously hard to find, and unbelievably expensive.

Initial performance results are understandably hard to obtain, however Al Papitto reports that with only 25hrs of port work into the his new ‘00R heads, they have already eclipsed the performance of his old Navigator heads with months of labor in them. These heads feature larger intake and exhaust ports, +1mm larger exhaust valves, and a dry exhaust port divider. Cobra R heads also require the use of a specific valvetrain not shared with any other modular application due mainly to their overall physically larger size. Al also claims R heads have too much port volume for a street/strip 4.6L application; only consider them with a larger 5.4L motor or a serious 4.6L race application paired with some form of power adder.

The Bottom Line: The best heads you can or can’t find for a Modular four valve motor.

You are as likely to come across a set of these Modular “Godfather” heads as you are to be Catherine Zeta Jones' next uterus masseuse. Though based on their performance abilities, you may want to start saving, just in case…

Stock Intake Choices: None (4.6L), ’00 Cobra R (5.4L)
Aftermarket/Modified Stock Intake Choices: Sheet metal
’00 Cobra R head dimensions: Combustion Chamber: N/A , Intake Port Vol.: N/A , Intake Port Entrance: 2.370”x1.300”, Valves: 37mm Int. 31mm Exh.
Stock Intake Choices: ‘00R
Aftermarket Intake Choices: Sheetmetal.

FR500: (FRPP)
The sole “aftermarket” offering of the bunch, these high flow heads feature a modified C head intake port combined with the smallest port volume of the group—it seems Ford meant to design these heads for high performance naturally aspirated applications. With the same small standard exhaust port as most other DOHC heads you will still have to remove a decent amount of material from the exhaust ports. Port entrance shape/size remains identical to C heads so finding an intake isn’t hard.

These heads are capable of producing power beyond 8000rpm, where earlier versions of the tumble port castings begin to lose their luster. FR500 heads are prone to the #6,7, and 8 cylinder cooling problems as well. Major intake port differences between these and earlier tumble port heads include a raised intake port roof, and a real short turn radius that better directs the incoming air into the combustion chamber; not over the valves like in earlier versions of tumble port heads. These heads also feature a dry divider in the exhaust port, which allows for greater flow, but also higher temperatures. Though improved, the heads can still use some TLC from a quality porter to smooth the roughly finished and newly implemented short turn radius, and the standard exhaust treatment.
The Bottom Line: Outstanding performance heads, with exceptional low and mid lift flow capability. The FR500s only real fault is that the newer ’03 DOHC heads provide near identical performance capability (much better on the exhaust side) paired with a cost differential that is approximately two-thirds less than the FRPP castings. Still a great choice for any application, the heads readily pair to a wide variety of stock and aftermarket intakes.

Stock Intake Choices: ‘99/’01 Cobra, ‘03/’04 Mach 1 & Aviator, ’03 Marauder, FR500.
Aftermarket/Modified Stock Intake Choices: Al Papitto short runner/ported ‘99/’01 Cobra, Sullivan, Aviator, '03/'04 Mach 1
FR500 head dimensions: Combustion Chamber: 53cc, Intake Port Vol.: 160cc, Intake Port Entrance: 1.960”x1.350”, Valves: 37mm Int., 30mm Exh.

‘03 DOHC head: (‘03+ Aviator, Marauder, Cobra, Mach 1, Australian Boss 260/290)
Featuring a nearly identical (though 17cc larger in volume due to the fact that they are also used on the much larger Australian Boss 260/290 5.4L DOHCs) intake port to the FR500 head, but combining it with a newly designed, larger and more rectangular exhaust port, these may be the best all around DOHC Ford heads ever manufactured. The improvements made to the intake port shape over previous years include a raised port roof and the introduction of a short radius turn in the throat of the intake port that helps assure the incoming air charge finds the combustion chamber. For those with a forced induction street/strip motor, these are without question the best heads available, and as with the FR500s, they should produce great power up to and beyond 8000rpm regardless of application. ’03 DOHC heads also feature higher quality head castings from the supplier, which is at least partially responsible for the modest increase in flow vs. earlier castings--chalk that up to Ford’s revised quality control standards.

Early runs of the ’03 DOHC head fell victim to the same #6,7,8 cylinder coolant flow problems as earlier tumble port castings. In mid ’03 Ford made a running revision to the ’03 DOHC heads that allowed for more coolant to circulate through the affected areas. A blue mark on the driver’s side head indicates an updated casting, and there are no additional revisions to the ’04 version of this design.

The Bottom Line: On all accounts these are the best modular four valve heads currently available. They combine the exceptional flow of a slightly larger FR500 intake port with a gigantic new rectangular exhaust port.

Stock Intake Choices: ‘99/’01 Cobra, ‘03/’04 Mach 1 & Aviator, ’03 Marauder, FR500.

Aftermarket/Modified Stock Intake Choices: Al Papitto short runner/ported ‘99/’01 Cobra, Sullivan, Aviator, '03/'04 Mach 1
’03 DOHC head dimensions: Combustion Chamber: 52cc, Intake Port Vol.: 177cc, Intake Port Entrance: 1.960”x1.350”, Valves: 37mm Int., 30mm Exh.


In Conclusion
Our panel of experts surmised that aside from the nearly unobtainable ‘00R heads, the ’03 DOHC heads are without question the right choice for your Modular four-valve performance application . The combination of a slightly larger FR500 intake port and modified throat region, coupled with a new larger rectangular exhaust port, and a relatively low price (due to it’s widespread use in the Ford organization) makes the ’03 DOHC casting the current head stud of Ford’s Modular stable.

After porting, the relatively small stock valves/seats become the most serious flow limitation; as such aftermarket replacements should be a serious consideration for those looking to squeeze every last drop of performance from their DOHC heads.
4V Heads

Ford has quite a few more 4V heads than 2V heads. The first type of heads are called “B” heads. These are found in the 1996-1998 Cobras and 1993-1998 Mark VIIIs. These heads are also known as swirl heads. The “B” heads have two intake valves as well as two exhaust valves. These heads flow 230 cfm at .500 inches of lift on the intake side and 145 cfm at .500'' lift on the exhaust side. There is a very unique item to the “B” style heads known as IMRCs or Intake Manifold Runner Controls. The IMRC is a computer that keeps the secondary intake valves closed until 3250 RPMs. In 1996 and 1997, they were made with aluminum and got very dirty. In 1998, Ford changed to a plastic style IMRC valves. Ford has this actuator to maintain torque down low and have good horsepower in the upper end. The heads flow too big for normal street use, hence the reason why Ford chose the IMRCs for these heads. The IMRC controller has been known to fail as well, causing a huge loss of power. Some people will go as far as deleting the IMRCs with a kit, but this causes bucking, stuttering and a loss of torque; I personally do not recommend this, even on a non N/A car. Eric Duncan has done some tests on IMRCs and found you can actually gain quite a bit of rwtq by having the valves open closer to 4000 RPMs than 3250 RPMs.

From 1999 to 2004, Ford switched to the tumble port heads. The tumble port style is meant to prevent condensation on the intake ports from dropping into the cylinder bore, as well as having a homogenous mixture for a more controlled, predictable burn. These heads flow better than the “B” style heads until .450 inches of lift; then the “B” heads take over. The 1999/2001 heads flow 225 cfm on the intake side and 145 cfm on the exhaust side at .500’’ lift.

Ford Racing came out with FR500 heads. These heads are another version of the tumble port heads. The heads outflow the 1999/2001 Cobra heads by quite a bit with 228 cfm on the intake side and 162 cfm on the exhaust side at .500’’ lift. These heads have quite a bit of meat of them to port but I personally do not recommend these anymore. Ford came out with even better heads, IMO. Expect to pay around $700 per head for these “jems.”

In 2003 and up to 2004, Ford developed what is probably the best “bang for the buck” head for the 4V motors. These heads are found on 2003-2004 Cobras, Mach 1s, Aviators and Marauders. The heads are still tumble port heads but much improved compared to the other years. The exhaust port is squared off at the corners, which is probably the easiest way of telling these heads apart from the other heads. Ford decided to use dedicated left and right castings for these heads as well which help keep cylinders 6,7 and 8 a little bit cooler. These heads flow 233 cfm on the intake side and 168 cfm on the exhaust side at .500 of lift. The FR500 heads do outflow these from .250’’ lift and below but the price more than makes up for them. You can find these heads for as low as $450 for BOTH heads.


Head Specs:

1996-1998 “B” heads:

Combustion Chamber – 52cc

Intake port – 107cc primary/115cc secondary



1999/2001 Tumble Port heads:

Combustion Chamber – 54cc

Intake port – 177cc



2003 Cobra Tumble Port heads:

Combustion Chamber – 52cc

Intake port – 177cc



FR500 Tumble Port heads:

Combustion Chamber – 53cc

Intake port – 160cc

4V Cams
Camshafts for the 4V are a little more scarce than the 2Vs. This is primarily since it’s double the work and double the effort. Readily available after market camshafts can be gotten from Competiton Cams, Crower Cams, Crane Cams and VT Engines. I highly recommend staying away from regrings when it comes to cams. This is because there is always a chance of some parts being off a few thousandths that results in having to shim. One thing you might notice is that the 4V doesn’t lift as high as the 2Vs do. Truth be told, there is no need. The 4V has duration that the 2V doesn’t. If the 4V is using 37mm diameter intake valves (stock size) lifting at .500’’, for the 2V to equal that same amount of air flow with their stock 45mm diameter intake valve, it would have to lift up to .821’’s. This is impossible and shows how much better the 4V actually flows when comparing it to the 2V. One question that comes up all the time is, “I’m going to supercharge my engine later on. What cams should I buy?” If you’re going to add a blower or turbo to your car, always select blower cams. They will add power N/A and once you put on that supercharger or turbocharger, they’ll add even more power.

Intakes
Unlike the 2V cars, the 4V cars have many options out there for complete intake manifolds. Both the 96-98 intakes and the 99/01 intakes can be customized to suit just about any need you have. If you must have the best, sheet metal intakes can be made, but at a price of about $3500.



1996-1998 Cobras have an aluminum, side-entry throttle body intake manifold with long runners. The runners curve 180 degrees into the cylinder head ports and in between them are things called “IMRCs” or Intake Manifold Runner Controllers. The job of these is to maintain torque by only opening one intake valve and one exhaust valve until a given RPM (which Ford set at 3250 RPMs stock). The 1996 and most of 1997 IMRCs are made of metal which get gummed up quite a bit from the carbon that is found after engine combustion. Some late model 1997s and1998s have a ceramic style IMRC plate that doesn’t get nearly as dirty as the 1996-1997s do. IMRC deletes are out there but unless you have a poweradder that is constant like a turbocharger or supercharger, you will lose torque and have significant driveability issues under and until 3200 RPMs. Eric Duncan did some tests and found that you can actually gain quite a bit of torque by making the IMRCs open up at close to 4000 RPMs. This intake manifold will only fit on B style heads.



The 1999/2001 Cobra intake manifold is a long-runner design, just like that of the 1996-1998, but it no longer has IMRCs. These intake manifolds flow significant better over the 1996-1998 and that’s one of the reasons the 1999/2001 gets its HP difference from the older Cobras. This intake manifold will fit on any tumble port style head.



The 2003/2004 Mach 1 has a unique intake manifold that is similar to the 1999/2001 intake manifold. It is a long runner intake in that the air travels between the runners, then down the opening and back up again to the cylinder head ports. This intake seems to make great torque but isn’t too great at high RPMs. This is one reason why the Mach 1s perform better when shifting around 6000 RPMs instead of 7000.



The FR500 intake manifold is the most unique design of an intake I’ve ever seen. It is not a short runner, it is not a long runner – it’s BOTH. The FR500 intake manifold has short runners that are controlled by throttle blades that are closed until they are needed. The long runners are used until 3500 RPMs, which then the short runners open up at. Unlike the other intake manifolds, this intake is made of magnesium. This intake manifold will fit any tumble port style head but it’s going to cost you a whopping $2500. Gains have been known to reach 40 rwhp and beyond with the FR500 heads and cams to compliment them.

 

[FirstOnRaceDay.]

excellent info, thank you all so much.

 

[FirstOnRaceDay.]

So you are converting your 96 to as close to Terminator 03/04 powered as possible, except with a nice and light Teksid block.... correct?

If those heads were professionally done then they are probably very close or better than 03/04 heads, but not better than PORTED 03/04 heads.
Glad to hear that you know to fix the spark plug threads issue.
Sounds like a nice build.

Make sure the pistons are compatible with C head valve clearance, not sure if they are different but you will want to know before it is too late.

Using close to 9 to one comp ratio will allow more power at less boost and IMHO is a good idea.

Also make sure your support is up to the task.
Air monitoring, fuel delivery, cooling and cooling air flow that stuff does matter.

after reading through the information on the heads listed bellow i couldn't quite tell why ported 04 heads would be better than ported 01's. it also says bellow that the 01 c heads flow slightly better even in stock vs stock condition so that further confused me. could you shed some light possibly? thanks.

 

[FirstOnRaceDay.]

anyone care to chime in? also i did not revieve timing gears or chains with my heads. will my 96 gears and chains work fine with these heads and an eaton? i have to get the heads squared away before i can began collecting the other parts for this build so some help would be great. also thinking about water meth spraying it and running windshield washer fluid (60/40 water meth). anyone have a system they like for the eatons? i've heard snow a lot but don't know much more about it.

 

[FirstOnRaceDay.]

bump

 

[GodStang]

Quick Thoughts:

Meth a waste unless you spray after the intercooler. Many many threads on this.

03-04 Heads flow a good bit more stock than the 99-01 Heads as showed above. They out flow across the entire lift. From above "the ’03 DOHC heads are without question the right choice for your Modular four-valve performance application " Also the 03-04 have water passages where I do not think the 99-01s do. This makes the 03-04 better for blown applications.

I would replace all cams and gears. We got all our from Tousely Ford for like $400 but this was in 2005.

 

[Happster]

Great write up. I have the 99 Navi heads on my 01 Cobra with a forged out low end and the 03-04 Eaton upgrade. Had to do some minor grinding on the heads (and block - the knock sensor towers) to get the '03 lower plenum to fit, but there was plenty of metal to get it done and she runs just fine. Some other mods, 2.8 upper pulley, 10 inch lower pulley, BBK cold air set up, long tube headers, 3-inch Magnaflow exhaust. Had to put the 03 tank and pump in too...my Walbro 255 leaned out at 3800 RPMs. Getting her dyno-tuned at Dez Racing now...can't wait to see the numbers. Minor pinging problem...probably the plugs. But she's almost done.