My question is which 5.4 performs the best, 4 or 3 valve ? Kenny Nunez

 

can you give a little more info like what years vs which?
i was about to buy an Expedition 06 w/ 3v trition but the my 02 Navigator i think got it as far as preformance, but idk the expo might not been tuned up so idk but as far as the 03-04 navigator there engines are to sluggish 4 me i mean 0-60 in 10+ sec .......but what are you looking at ?which years?

 

I believe , .that 04 was the last year for the 4 valve, does the 05 or 06 seem to perform better, I am thinking about installing one in my 68 100, the 3 valve engines are newer and finding a low mileage one is easier.

 

yes they will perform better then the 4v 03-04 years i would go with the 05-06 3v

 

I would go with the 5.4 4 valve as the DOHC has been proven to be the more tunable engine. I would like to have a set of cams ground to match the profiles of a 4 valve Honda, Kawasaki or Suzuki rice rocket. They make good horse power at over 10,000 rpm, idle nicely and give great fuel economy. The DOHC engines are not near their rpm and power limits in the Mark VIIIs, Navigators or Mustangs. There is still a lot to be had from those engines. A well tuned Mark VIII should be able to do well over 200 mph on Bonneville with good rods and cams and without a turbo/super charger.

 

A pretty much stock Mark VIII with very minor changes has already been 182mph out there back when they were in development. More here:
1993 Bonneville Mark VIII
JL

 

I believe the engine and transmission speed was redlined by Ford to keep owners from going as fast as the cars were capable of going if they had good rods.
I know about that car as I'm a member of the Mark VIII club(s) also. The last I heard the museum was going to dispose of that car and one of the clubs was trying to aquire it. There was also a member who was trying to buy it. I don't know what finally became of it. Do you have any info on that?
Jerry Wroblewski is/was a transmission engineer involved in the design and development of the 4R70 trans. He has built and upgraded many 4R70 transmissions and his mods are/were widely used by the club members. The last I heard he worked for Rousch and divided his time between Michigan and Arizona.

 

Jerry is a personal friend of mine. He hasn't worked for Roush in years. I have no idea on what happened to that car.
JL