Hi everyone New to website and ford land. Been a old school v8 commodore fan mostly, however dad has given me his AU and i'm sentimental. But anyhow back on subject...

The big difrence i see between the mainstream mentality of the ford six vs other stables is in the RPM/diff ratio department.

The way to be fuel efficient is to make power at low RPM burning as litle fuel as possible close to detonation, which is retarded on the mapping of the engine management.

Generally speaking fast isnt economical, so consider the following:

Programable engine management with high flow injectors, a Bosch Motorsport fuel pump, BP Ultimate or Shell racing pump fuel will need to be used. (higher engine speeds and other factors will place too high a demand on stock stuff, and higher octane will be needed otherwise detonation will occur).

Camshaft choice. You guys know better than me about the common choice cams, but the grinds that make power 4000-7000 RPM are the ones you want.
Yes double valves springs etc is the go but just as important are the fasterners holding your engine together! ARP and half a dozen other companies do cromolly studs to hold your head on and caps down. And then Consider better con rods. Most ppl i know who build motors use H beem rods instead of I beem. I believe ACL DO awsome high silicon lighter than stock pistons with huge ring lands. The bigger ring lands give more support to the rings. And they offer a 30cc dish to lower compression too (more on that latter).
The AU crank is apparently the way to go. Ballancing is not as important in the i6 as is the case in a V configuration, but if you want to reduce engine harmonics and cause vibration and oil leeks get the assemble ballanced.

Head porting is ussually the way to go to make the heads flow. And making the ports match between manifolds and the head. With a non restrictive throttle body.

Doing these will allow the motor to rev and make power upto 68--RPMish and hold together if treated well. Atleast i am hoping it will becasue this is my plan
But please consider not going the asperated method of producing power. Bang for buck, lower your compression ration and turbo charge the engine!

A thick decrompression head gasket can also lower compression ratio.

WIth a lower than standard compression ratio and using Forged pistons with an "Electronic" speed controler.
A custom tuned length exhaust header with a T4 flange. And a GT balll bearing medium font case flow compressor. Plumb the gas with 3" stainless pipe (better thermasl properties) into a decent front mount intercooler (fully sick!) and then plumb that into a sheet metal fabricated plenum.

Feel free to run 14psi low 28psi high boost.

Now this is where you start braking diffs anfd gear box's people!

Fully sick.

In regards to the original question, don't f**k around with going smaller displacement. For the money buy a different engine or if you get the falcon engine balanced properly the bottom end should be able to hit 7000 now worries.

Did I mention anything about side load in any of my previous dribbles? At 7000rpm I wonder how long your rings will last.

i think its because of the long stroke of the 4.0,

I have heard that. But if you use better rods and bearings one would beable to get around this?
All stock internals would need to be changed in other motors to make it tuff enough.

yea true, but having a high rpm isnt everything..

yea true, but having a high rpm isnt everything..

What parts a wrong? I did actually consider putting my 308 in the AU. But i want a 6 cylinder in this car.

If we cant get the 4ltr reving to 7000RPM i'm chucking the thing out. My cast iron v8 which is basicly an engine designed 100 years ago that uses push rods to operate the valves can rev to 7000RPM all day long reliably and short stints upto 8000RPM and this motor cant and its built in the 21st century.

I just got dad some maccas and on the way back the AU did over 80kmh in first gear, i have an auto. That will make the diff ratio about 3.08/1 no?

The valve train would easily deal with revs, it's the long stroke with comparatively short rods thats the problem, along with the heads simply not flowing enough air to make usable power at that RPM, even when ported.

and sheet metal manifolds...... you need to stop reading street commodores.

I beam vs. H beam has been done to death. If you want to built a high reving N/A engine you dont want the extra weight of a H beam and at those revs a cast piston will not live.

As far as ARP doing head and main studs for this engine... you have to be joking. NO ONE makes them for this engine.

ACL don't do a 30cc dish for this engine as that would give you compression somewhere in the 7:1 range,

About the only thing you got right was the turboing this engine is a good idea.

It wasn't the best idea to come on here and start lecturing every one on how to make power with an engine we have all been dealing with years yet you obviously know nothing about.