5.4 shortblock with 4.6 heads?

not enough airflow to make as much HP as a 4.6 or stroker 5.0.

So 3v+ or bust?

Riley

You will gain something. remember the 4.6 and 5.4 are modular engines. They use the SAME heads. I would recommend a ported set, that will easily flow enough. The 3v swap is very labor and $$ intensive. The 5.4 2v is reletively plug and play. You have to make ex and intake manifolds work, and possibly a cowl, i dunno.

98blackstallion said:

so gaining 8 tenths of a liter isnt going to make a difference.

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In a sense, it may not make much of a difference. I'm going to guess that what billfisher was saying is that a 4.6 or a 4.6 stroked to 5.0 would have a good balance between a stock 4.6 and a 5.4 for both volume and velocity in filling the combustion chambers. You're heads can only flow so much, and putting a massive block underneath them that can never be filled with stock 4.6 2v heads is basically a waste of time, and you wont get enough cylinder fill. Putting the same amount of a/f in a 4.6 bore vs a 5.4 bore IMO would net more power due to higher cylinder pressures.

That would be my guess, but I'm not sure exactly what he (billfisher) was refering to.

98blackstallion said:

Ok guys is this swap possible and if it is will it net any gains? I have all the bolt ons for my 4.6 but it blew so i figure i would upgrade to a bigger sized motor...Help me guys

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You could go to a 5.4 but it will be a bit of work and will give you more low end but about the same higher rpm hp. Yes you can use the 4.6 heads but that would be pointless b/c they are the same.

What about 5.4 heads on a 4.6 bottom end? Any gains in that? I know its the complete opposite of the question, but im curious to see which would net better results.

5.4 and 4.6 heads are the same.

if you can fabricate stuff just swap a 5.4 3v or 5.4 4v in.


5.4 3v fits under hood

5.4 4v doesn't. and you have to fabricate the entire intake for 4v.

BB 5.0 is the best compromise for torque and hp. efficiency drops to around 84hp/liter for 5.0 using 2v.

5.4 3v with ported heads can reach nearly 100 hp/liter.


and that's with a dyno mule.

to add to what bill has said... the issue with the 5.4 is that there just plain isnt enough air to feed it correctly. i gave up on this idea myself when i reached the 12k mark in parts alone and still didnt meet my HP desires... however i was shooting for 500....

the issue with the 5.4 is that it has to get more air...SOHC heads will NOT do the job... ported or not.. just no. it will need 3v at least, or 4v (people still argue which is better) but leaning to the FR500 heads as the biggest plus for the heads area... most people working this are switching to cobra R or the new GT heads as they are the best combo. then adding in heavy cams (more displacement forces the need for a lot larger duration and lift cams, this causes isssues for springs) to get the air to get into the chamnbers... and yes, this will require oversized valves.

after the valvetrain/heads are to size the biggest issue has been the upper and lower intake manifold. the cobra manifolds have issues feeding the 4.6 at high RPM and after around 350 RWHP.... so those that either use adapters or cut and widen the cobra unit are killing the use of their pricy heads. MMR sells a nice piece (ugly as sin) that gets the job done for a short runner (think it was 9") sheet metal intake... but i think its disallowed in alot of classes (as all sheetmetal intakes are). for legal it seems to come down to getting a custom one done with around 13" runners (similer to the cobra R) if not going high RPM, or just getting the cobra R (if you can track one down). you will of course need the entire unit ported if its a cast piece.

once that is done its time to either live with crappy log type headers or omve into the custom bent long tubes. i heard that bassani has jigs for the 5.4 in a 4.6 setup... and rumors of kooks and hoker LTs working... but BBK, mac, and just about everyone elses wont fit without a lot of work (with a hammer) on the pipes. then you have to have a midpipe fitted to it (yes it will be in a different location then the stock piece)

anyhow... getting the picture? there is a lot to it... i'd love to do it... but i wont till i either get my 140k a year job... or ever... lottery anyone?

Torinalth