The 3.9L/4.0L Inline 6 Modification Guide


Exhaust: 2.5" Mandrel Bent is recommended. Suggested brands are Lukey or Redback. Average Prices range from $250 to $350. Expect only a small power increase.
Most people like to order these without the rear resonator for a louder/better exhuast note.

Extractors: Pacemaker, HM, Wildcat, JMM, Lukey and Hurricane are some of the more well known brands. Pacemaker and JMM are generally regarded as the best brands to try. Longer, small diameter pipes will generally give a good gain in torque across the rev range, whereas shorter, large diameter pipes will give mainly top end gains only (Good for Blown motors). Combined with a decent exhaust gains of up to 15rwkw could be made. Look for mandrel bends for best results. Prices Vary depending on model - $300 to $550.

Catalytic Converter: Generally a High Flow cat will give you little or no improvement if your current cat is in good order. Standard Cats however are only 2.25" diamater so it may be worthwhile upgrading to a 2.5" high-flow if your budget can extend that far, or modifying the stock one. Average prices range from about $100 to $300.

Camshafts: Good gains can be made in this area on the Inline 6.
Wade Cams do some good regrinds for the I6 such as the 1004, and a similar high lift 977B, as well as the newer and popular 1636 & massive 1521a. They offer a discount to Fordmods members also. Because these are regrinds it is neccesary to use shims, which can be borught from Ford.
[/i] cams are generally regrinds and also need shims, but they do offer a specially modified rocker gear that reduces the number of, or elimates the need for shims.
Crow do Billet Cams which are more expensive, but negate the need for shims. Such cams will lower idle quality a bit, but can give huge gains in power - from 5-30rwkw (dpending on other mods done).
surecam is another that you may wish to check out. They have a few profiles available, and also do custom grinds which have seen some fantastic results.
It is recommended that you have extractors and an exhaust before installing a cam for maximum benefit. Some cams may also need upgraded valve springs to be installed.

Headwork: Getting some headwork done can be quite expensive but will allow the engine to breath much better. Larger valves can also be installed to aid in this area. The XR6 Head already has slightly larger valves but can still benefit from some port work. JMM sell modofied heads, but many 'Head' shops can do this work to suit your needs. Prices range from $400 to $2000 depending on how much work you want done. Shaving the head, and/or using a thinner head gasket to boost compression will also produce small gains in power and torque.
Using the Ford Genuine AU head gasket will result in a small compression boost when used in E-series, and are also more reliable.

Forced Induction: These motors respond really well to forced induction with even basic low boost setups creating more power than many worked N/A motors. Depending on what you want (Turbo or Supercharger) there are a few kits available, or you can make a custom setup. Visit Snort Performance, CAPA or Raptor superchargers for information about their kits.
Prices start from about $5K for a basic setup.
Often overlooked, but one of the most important steps if considering this route, is engine management. If you plan to use forced induction, incorporate some sort of aftermarket engine management into your budget.
More info on Forced Induction {DESCRIPTION}, and a DIY guide {DESCRIPTION}

Induction: EA to EB Multipoint can have an XH Snorkel fitted to increase airflow. EF-EL can fit an AUII XR8 or EL GT Snorkel for the same effect. These are around $30 from Ford.
K&N, BMC, Unifilter or other similar panel filter can be placed in the airbox for better aiflow as well, or you can create a custom pod filter setup. It is recommended that if you go with the Pod Filter setup that you retain the airbox, or at least create a heat shield for it - otherwsie you will be drawing in hot air. Filters usually cost around $120.
EF-EL can have a custom mandrel bent pipe made to replace the restrictive plastic pipe between the throttle body and airbox. These look good and increase flow for around $150-$250.
EB-ED can use an EA Multipoint intake tube between the throttle body and airbox for a very minor gain (these can be found at most wreckers).
Some people also convert their EA-ED's to the Broadband Intake Manifold found on EF-EL, this increases bottom end torque. Conversion usually costs around $300 or so for parts (from wreckers).

Package Deals: If you can't be bothered doing all these modifications yourself, or would rather go to the one place to get everything done then there are some places that offer package deals. Some exhaust shops can do a Full Exhaust/Intake system (Extractors, Cat, Exhaust & Intake Piping), some places offer chip/cam packages, or there are places that do the lot.
Jim Mock Motorsport (JMM) do a series of DEV kits that range from basic exhaust/intake work to head/cam packages from about $1K to $6K.


Thermofans: The clutch fan on the front of EA-ED motors not only sounds awful but robs the engine of power. Upgrading to EF/EL Twin Thermofans is an effective worthwile modification.
To do this you can buy a kit from Battens Performance, or try doing it yourself with a Davies Craig thermo-switch kit etc.
You can also convert smartlock equipped EB-ED Falcons to use an EL ECU which have outputs to control them. The thermofans are quite expensive from ford new at around $400, but shouldn't be too expensive from a wrecker. They are also available at Ozeparts for approx $180.

Engine Management:
Whether trying to get that big cam or turbo to run, or just for improving driveability - engine management is becoming an important modification for the 4.0L six.
Visit the ECU & Fuel System Forum for a wealth of information regarding this topic: Particularly the {DESCRIPTION}.


Small Stuff:
Spark Plugs, Ignition Leads, Injectors, Fuel pressure reg, throttle body etc.
It is recommended to keep your car well maintained.
However, I believe it is not worthwhile to waste money on fancy leads and plugs if you are trying to chase power. There are better ways to spend your money. Upgrade the small stuff when you have exhausted other avenues.

Ignition Timing:
Advancing will provide a small improvement in power, but may also mean you will have to run a higher octane fuel.
For a quick run down on how to do this see {DESCRIPTION}



In what order should I do these mods?
There is no set order that you should be performing these mods in.
However, to get you car up and running with a nice increase in power for the minimum cost you can't go past the exhaust and cam combo.
You generally won't notice much difference upgrading the intake setup, leave these mods for later if you're on a tight budget.

What is the best Product X?
There is a lot of debate here at Fordmods over what are the best exhaust systems, the best cams, the best snorkel etc.
The fact is, we all have different goals, budgets and cars in differing conditions. Some are manuals, some are auto. Some people have a 2.77 diff ratio, some have 3.45. Some people might like lumpy idles, where some despise them.
What works for one person may not work for another.
Therefore, there is no best or worst product - so please refrain from asking that question on here. It will just spark up a heated debate.
If you do some research on the products you may learn their characteristics, and see some of the results people have achieved (dynos and 1/4 mile times).


Other Info:
Please also visit stockstandards excellent thread about engine retrofits {DESCRIPTION}
Retrofitting a later motor can be a great way to freshen up your vehicle, and make more power.

Also, if you have a question related to the Ford six, before making a new thread, check to see if it is answered {DESCRIPTION}, or if it has been covered before by performing a {DESCRIPTION}

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