There is a lot of debate around the 03 and 04 head cooling mod. Is it really necessary? Will it cause a problem? Is it just piece of mind? I'm ok with all of these statements. I wanted the piece of mind so I made the decision to get it done on my 03 Cobra with only about 31k miles on it.
What is the head cooling mod and why is it necessary? The head cooling mod is a way to increase coolant flow for the drivers side cylinder head. The passenger side cylinder head has the coolant flow from the front of the cylinder head and out the back, where it is routed to the heater core. the drivers side cylinder head has no escape for the coolant. It essential dead-ends at the number 8 cylinder. Under extreme driving, people have reported a 'head tick' which is due to the number 8 cylinder exhaust valve overheating / getting burnt out. There are two types of head cooling mods. One punches out the freeze plug at the back of the cylinder head and routes the coolant to a Y on the passenger side, then returns it all back to the heater core. To install it, the transmission needs to be removed. This is typically done when there is an issue with the throwout bearing, or the bearing retainer, or the clutch. The other type knocks out the freeze plug at the top of the cylinder head. For this one, the supercharger needs to be removed. This is typically done when the supercharger is removed for upgrading.
I chose to do the cobra engineering head cooling mod. I like the idea of routing the coolant through the back of the cylinder head, just like Ford designed for the passenger side cylinder head. I also found a crazy deal on the cobra engineering HCM from someone that was parting out a cobra motor that had this installed. I got it for 160$ shipped to my door. I also emailed the guys at cobra engineering and they sent me two new O rings, for free! Great guys over there!
Cobra Engineering HCM
The installation process was pretty straight forward. I had the added opportunity of my best friend having a lift! That made this entire installation take about 6 hours start to finish. I did have to pull the mid pipe again and replace the header flange gasket on the passenger side - apparently they are a 1 use gasket. I ordered a new one from FelPro. Here's a pic of the car up on the lift.
Here's a rough run-down of the install. Remove the shifter bezel and handle. Unplug the oxygen sensors and drop the mid pipe. Remove the driveshaft. Note, while the mid pipe was out, we welded in a bung for a wideband. unplug everything from the transmission and remove the shifter cable. Remove the bolts from the trans to the bell housing and pull out / lower the transmission. Then remove the bell housing. Drain the coolant using the plug in the block. To knock out the freeze plug on the drivers cylinder head, I used a big common screw driver and a hammer. it came right out. Then I disconnected the coolant line from the heater core and removed the fitting from the cylinder head. The EGR tube needs to be 'modified' so that the HCM fitting will fit. We bent this out of the way and away from the engine without disconnecting it. Then the HCM can be assembled and installed. The little retaining bolts are tough to install, but after some words of encouragement, we were able to get them installed. It doesn't call for it, but we used some RTV to help seal the fittings with the new O rings. Added security. Everything gets put back the way it came off. The coolant needs to be topped off after this process. Mine took about 3 gallons. It was filled up through the plug on the crossover tube (as per ford instructions). We modified a small funnel and 'screwed' it into that plug hole. After the thermostat opens a few times and the bubbles go away, its done and full. Put the plug back in, gently. Its an O ring so it doesn't need to be super tight. I also found that my stock clutch quadrant adjusted itself when the cable was disconnected from the transmission. I held the pedal down to the floor with my hand and adjusted the quadrant to be about where it was. In hindsight, I should have marked it. Or installed an aftermarket quadrant and firewall adjuster. Below you will find some pics I took of the HCM while the trans was out!
Now I have my piece of mind!
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