Barra NA performance

Hi guy,

Looking to biuld a NA barra 4.0lt to a mild motor about 320hp at wheels.

I am restoring my ute , and now time for motor rebuild, she Done well 275000 ,

My 2005 BA mkii XR6 , l use to carry my tools to work, at start and at end if my swing, mainly highway driving.. about 659kms oneway.. she pulls good on highway, passing roadtrains, , can get to 200kms ++ quick on highway when passing, but not a breast in town which is ok for me..plus use with trailer some times

I had some basic work done, underdrive pully, blackcat exhaust and headers, 2.5 tune/ remaping -l was told on Dyno she about 240hp at wheel. Which not far from stock, had truetrac LSD upgrade ..it will handle upto 700Hp so l told.. but 320 to 400 I OK for me.

I see so much about turbocharging,

Barra 6 is abig motor, but not see much about biulding na performance...

ok any idea guys

Back in the day, we build at home allot na good HP motors

Before all tech came in... tech not bad thing, seems we lost the knowledge to biuld good performance NA motors

Remember only looking for mild rebuild,

I don't think its a case of losing the knowledge to build an NA engine, its just that turbocharging has come a long way and is a very easy way to make a lot of power. The usual formula for NA performance is really still the same. You need to increase airflow into and out of the engine. A good start is the intake, headers and exhaust system but if you want o get serious then you're going to most likely need to look at more aggressive cams, head porting and raising the compression ratio, all of which become quite expensive modifications when compared to a basic turbo kit.

As Andre said, forced induction is a, relatively, easy bolt-on, especially with the kits and parts swapping available.

In your case, I'd first ask what you expect from the engine? is it outright power for high speed driving, increasing the mid-range torque for cruising with it loaded up/towing, better fuel economy for laden cruising, or a mixture of them all?

The second thing is if this is your primary drive, or are you able to take it off the road while the engine's being built - bearing in mind there may be unexpected delays for parts, etc? If the first, I'd suggest looking for a running, if high mileage, engine as a core (you may be able to recoup that expense selling the 'old' engine back as a runner) to have it built up with the internals you want/need for your build to be a simple swap over.

The actual parts will depend largely on what you actually need, and the fuel(s) available to you. Personally, I'd probably be looking be looking at higher compression pistons - if the octane allows, around 20 thou' quench, valve guides and valves, if needed, with a 3+ angle seat and valve cut of ~1mm intake seat width, ~1.5 exhaust - your shop should know what to do. Some light work taking the ridges and lumps out of the port and clean up the bowl area. I'd look at keeping the stock camshafts, or 'maybe' use a higher lift with around the same duration if available - checking V2P clearances - something the 'shop should do.

Maybe look at some filter housing/intake work to make sure it's getting the coolest air that's practical - I don't know how good the OEM set-up is, but most are a good option with a paper or GOOD aftermarket filter element.

Then have the tune fine tuned on the dyno'.

Where is the vehicle actually based? You have Thailand as a location, but mention "road-trains" that are usually an Australian thing?