Intake Manifold Runner Control

[DEFYANT]

When do they open? On my 98 Cobra they open at 3250 RPM (:D ). When do they open on the 04 MM? Is it the same RPM? Just by listening to the car, I was thinking they were opening around 2500 RPM. No problem with the car, I'm just curious.

Thanks.

:beer:

[KilledKenny]

The Marauder 4.6 DOHC does not use Intake Runner controls. As far as I know, the 4.6 DOHC car engine has not used that system since 98. Previous years it was tuned to open at around 3000 RPMs.

[DEFYANT]

You are correct. After you posted, i dug around on SVTPerformance and found some interesting info on our heads...

Heads

B-Heads (96-98 Cobra; 93-97 Lincoln Mark VIII; pre-99 Lincoln Continental)
Nicknamed the “swirl port castings.” They have twin intake ports, one primary and one secondary, with the infamous IMRC plates. Not good for a N/A head, best used in boosted applications.

C-Heads (99-01 Cobra; 99 Lincoln Continental)
Nicknamed the “tumble port heads.” These heads have a single intake port with a smaller cross section which boosts airflow velocity. Good for midrange torque and power production. Good N/A street head but power production is pretty much limited to 8k rpm.

FR500 Heads (FRPP Catalog)
Basically the same as the C-Head but with a larger intake port. Capable of power production beyond 8k rpm.

03’ Heads (Cobra; Marauder; Aviator; Mach 1)
Possibly the best flowing small displacement head. The heads have the same flow capacity as the intake side of the FR500 head, but with a larger rectangular exhaust port. The best all around head and the absolute best for boosted applications.

*Note*: There is an unconfirmed report of “blue stripe” heads now being produced to fix the ticking problem experienced by a number of 4v owners. They can be identified by a blue stripe painted on the back side of the head facing the firewall. It is rumored that they have better cooling passage layout compared to early 03 production castings.

Navigator Heads (99+)
Same intake port design as the C-head, but with more volume. It also has the same small exhaust port as the B/C heads. Requires a modified 99-02 or custom sheet metal intake.

[Krytin]

That was some good info!! Thanks!

[JACook]

You are correct. After you posted, i dug around on SVTPerformance and found some interesting info on our heads... NB, this info is pretty much a lift from the December, 2004 issue of "5.0 Mustang and Super Fords"
magazine, titled "Six Times Four" aka "Ultimate Four-Valve 4.6 Head Guide". I won't pass judgment on the
"ultimate" claim, but it's a pretty thorough piece. If you can lay hands on a copy of this issue, you'll also
get some photos and airflow specs, both stock, and as ported by several different head shops.


*Note*: There is an unconfirmed report of “blue stripe” heads now being produced to fix the ticking problem experienced by a number of 4v owners. They can be identified by a blue stripe painted on the back side of the head facing the firewall. It is rumored that they have better cooling passage layout compared to early 03 production castings. There were some rumors floating around this board that the later '03s with the 3G-120-AB or later labels
on 'em were the improved cooling variety. I can't say first hand whether this is accurate. My '03 has
3G-120-BB on the label, and there is also some blue paint visible just under the driver-side cam cover, but
it's on the intake face. Haven't looked at the back of the head yet.

Can anyone confirm the calibration label rumor?
(NB, I don't hear any ticking yet, but I only have 18K miles on the clock...)