So I have my 5.4 motor complete out of a F Series truck,for my 2003 GT. I also have a complete 4v out of a 9? Mark 8 what are the diffrences in the Mark 8 motor and the 99/01 Cobra heads? On the same note will these heads go on the 5.4 block? If I read correctly the gt40 uses a 5.4 block and pretty close to stock 03/04 cobra heads. What is keeping me from trying this setup. A 5.4 is gonna be wicked a 4v 5.4 will be insane

 

The Ford Cobra R/GT/GT500 all use a special 4V heads that is no where near the same as a 03-04 4V head. However, any 4V head will bolt up, just you have have to match the parts accordingly.

 

the mark 8 motor uses B heads IIRC ( I like B heads better than C heads for intake options). There are differences in front covers, assorted gaskets and intake design. All in all, you should be able to use that 5.4 block and any 4v heads and make a bastard of a strong motor. You'll spend a fair amount of money on cront cover stuff and timing components but it's not super expensive... several hundred if you buy all new parts.

 

a 5.4 4 valve....hello torque!

 

do it man... do it. I'll help you.

 

ha ha....I wish.

 

Hi, I just joined because of this thread and the 5.4 2V thread.

I have done this in my 03 cobra, it was a piece of cake. I got a complete 99' Navigator block w/ RR adapter plates and a 01 ported intake. Motor dropped right in and runs great!!

Bone stock it turned 300hp and 360tq in 100 degree summer heat in South Carolina. The only problem I have is with the intake, the power just dies at 4600rpm or so, I don't think the 01 intake can flow enough air. I'm working on solving that problem and also adding a T-trim before summer.

I ran a 13.1 @ 106mph with my really bad driving.

I know the power is low, but I think with a better intake it would pull 330hp and near 385 or so of tq. I'd recommend this swap to everyone!

 

Your the guy I was hoping to respond to this post. So I can just use the Mark 8 front cover pieces? Are the cover pieces specific to a 5.4? If so I am going to have to source the parts from a GT or GT500. How strong is the 5.4? Are the blocks and rotating assemblies power limitations close to a 4.6? I would imagine to wouldnt be able to handle that high of a rpm due to the rod/stroke ratio is so much higher. Is this the right thought?

 

I might be able to be of some assistance. The Mark 8 front cover will not work, the cover, as well as timing chains, are specific to the 5.4. You can source parts from a 99-03 Navigator as well, they had the 5.4 DOHC 4V's. The 5.4 block is as strong as you need it to be to live well into the 800-900 hp range, probably higher. You will need a quality piston and rod. I have heard you can not spin the 5.4 as high as a 4.6, but I have not heard exactly where a 5.4 will safely rev to. A lot of that would depend on the quality of the valvetrain components.

 

yeah, front covers are different, so are timing chains and tensioners and such. Not a super big deal but find a navigator motor (99and up used 5.4L 4V) as a donor if you can... it'll save you some money. The RPM window is a little smaller than a 4.6 but with an intake that can support it you can do 6500rpm on a built bottom end. On a stock bottom end I'd shift at 5800 at latest.

My motor will be able to spin to 6500 with my valvetrain and the bottom end parts I'm using (with better cam and springs I could conceivably do 8K rpm).

 

What do you rec. for bottom end parts? Is there a stroker crank avaialble for the 5.4?

 

anything is better than stock, so depends on your budget. Mine was kinda tight so I stayed with probe pistons to shave a couple hundred bucks but I got perfect circle rings, and nice (killer deal) H-beams. I upped the cost a bit with my choice of ARP head and main studs and hard bearings but it's worth the little extra. You could bump the cost by 500-1000 bucks and go with a scat crank and billet rods and Diamond pistons but it's not really needed for a primarily street driven car. If you race HARD then those parts are better options.

Don't stroke out the 5.4. It's not worth it. The stroke is already very long and increasing it really isn't going to help. If you want more inches, then go 30 over and call it done. That's a 335ish inch engine that can make 400bhp in 2v and much more if your top end is radical enough and you add more valves.

 

5.4 4v sounds nice, but all that trouble for 300 doesnt. but here is a good website to get some parts

http://karkraft.com/