[BigEag205]

Welp, I had my motor completely redone last winter with all forged internals compliments of Eagle's stroker kit. At the end of the summer, I blew a plug out of #1. After this, I've come to find out about the 4 thread design of the Cobra aluminum heads and am not happy I didn't know of this prior to my motor build. My question is, I hear the 2004 cobra heads had 9 threads, but i dont really want to buy new heads :/ . I hear theres a way to make my 01 heads 9 thread? Hopefully someone with experience will chime in and help me out...what's the best route to take with this? I plan on adding boost and nitrous to it after i fix this so i dont want a quick fix. It need's to be done right and the best way possible...I can have them machined if possible.

[WickedSnake00]

As far as I know you've got 3 options, or at least there's 3 common/easy ones.

1.) Easiest/cheapest is to just helicoil it. Lots of guys have had good luck with these. I used some for my exhaust manifold bolt holes.

2.) Timeserts. These are threaded inserts, but much bigger and heavier than helicoils. They might give you a few extra threads.

3.) 04+ DOHC heads. Doesn't have to be Cobra, Mach 1, Marauder and Aviator heads all are the same and have the cooling/9 thread revision.

Or I suppose if you can find a machine shop they could bore out the spark plug hole, and then tig in a threaded slug to give you 9 threads. But this would also require heads off, and would just generally be a pain in the dick.

[BigEag205]

oh, it'll be a PITA anyways. I dont want to take the chances of ruining my new pistons by keeping the heads on it while doing this. I've used helicoils before, but not on something with high compression such as spark plug holes, and the fact that they can slide out when changing plugs scares me. I've read on timeserts and theyre steal, there for not transferring heat at the same rate as the aluminum heads and sometimes causing pre-det problems. I thought about tigging the holes up with alum then just rethreading them, but im scared of warping the head while doing that :/ ...

Your post about all 04 heads being the same (Cobra, Mach 1, Marauder, and Aviators) intrigues me and I will def look into that because Im sure that would be cheaper and easier to find than having to look specifically for 04 cobra heads which has also proven to be a PITA so far. Are all the dimensions, bolt holes, cooling revision, strength, and every aspect of the head the same? I've entertained the thought of buying bare 04 heads and just buying cams and springs and such as money is available. I dont plan on driving it this season atm due to his problem so we'll see

[WickedSnake00]

Originally Posted by BigEag205 Your post about all 04 heads being the same (Cobra, Mach 1, Marauder, and Aviators) intrigues me and I will def look into that because Im sure that would be cheaper and easier to find than having to look specifically for 04 cobra heads which has also proven to be a PITA so far. Are all the dimensions, bolt holes, cooling revision, strength, and every aspect of the head the same? I've entertained the thought of buying bare 04 heads and just buying cams and springs and such as money is available. I dont plan on driving it this season atm due to his problem so we'll see

As far as I know they are identical completely. It's just a manufacturer line, it's the 04+ Ford 4.6 DOHC head. They're all the same. I'm pretty sure if you cross referenced them in a Ford catalog the PN would be the same.

If you're really hard up and just want to get heads cheap and fast, even the 99-01 Continental heads would work. They're the same as the 99/01 Cobra heads, so they're 4 thread and don't have the cooling revision, but they are dirt cheap and available just about everywhere.

When I was looking at parts it was funny to see the premium people would put on and actually pay for "Cobra" parts. One place was charging $1400/head for Cobra heads, but like $800 for a Marauder of the same year. Another guy wanted tons of money for his "03 Cobra block" when it was just a run of the mill Romeo block you can pull from any 96-98 or 01-04 Mustang.

[BigEag205]

Yea, I def don't want to go back to the 4 thread. I'll hold off if I have to. And ya I've noticed the block price differences before and how they were interchangeable. Now that you brought it up and I think about it, the only diff is prob the cam profiles. You made my week by bringing that point up haha

[na svt]

You can install 9 thread "Timeserts" and that can be done with the heads installed. Helicoils will work but are a temporary fix.

Most plugs blowout due to being overtorqued or having been removed and replaced too many times while the engine is hot. If care is taken when replacing the plugs the 4 thread heads can be very reliable. Timeserts can be installed without removing the heads.

All 03/04 4v heads are the same (Aviator, Mach 1, Marauder and Cobra) and cams are the same also. Do not use the 03/04 intake cams, they have 12 degrees less duration than the 99/01 intake cams. The exhaust cams are the same in all 4.6 4Vs.