[nharv88]

Hi everyone, been thinking bout a sierra build.

H25A V6
maybe twin gt2052r or GTR stock turbos
vitara gearbox
*or*
G13B Twincam with gt2052r turbo (best response from what i can figure)

prado (or other constant 4wd transfer)
hilux diffs
Disk brakes all round
31x10.5x15 tyres
15x7/8 sunraysias

i kinda have a feeling that is constant 4wd was doable it would have been done. thought it would be nice with the extra torque (i prefer traction to wheelspin)

i saw a couple of H25A conversions on here but never seem to finish it

Under NCOP we can legally fit a turbo 2.5L. dunno how it would drive, handle etc with the H25 but it is all aluminium

[Gwagensteve]

That's a very complicated and expensive way to build a car that won't be much chop for anything. Heavy and bulky diffs with tiny tyres and far more power than the chassis can handle. Not capable off road, unable to use the power on road.

Just my 2c.

Steve.

[nharv88]

are there lighter diffs that will be stronger? i just dont wanna have a tough engine with weak drivetrain.

[nharv88]

and i would prefer to keep it standard ride height or minimal lift

[jdk81]

Manufacturers make other vehicles similar to what you want.

suzuki gv
subaru Forester
prado etc

[whincup]

i personally don't like constant 4wd as that would put more stress on the driveline/tires, etc. but if you have the capability and the willpower to do it, then do it. i love seeing unique stuff thats rare or never been done before

[pezz]

What is the intended use of the car once built?


The answer to that question should dictate the build direction

[Red89]

There is at least two guys in WA that are competing in 2.5 V6 powered Sierra based vehicles, both with Vit auto and Sierra TC, one on Lux diffs and 37's one on WT diffs and 33's. The only dramas they have had is the one on 33's keeps doing TC's.

[nharv88]

High Torque (H25A Turbo would have that in spades, the reason i wanted to upgrade diffs)
Good response (use of small turbos so the boost comes on as early as possible, yet big enough to flow 9k on G13B)
Mainly on road but would like it to be capable off road. camping and fishing mainly.
Like it to be reliable ie. i dont want broken gearboxes, transfers, diffs etc
i thought a constant 4wd system would improve traction on road for a boosted engine, and offroad lock diffs as usual.
i have little first hand experience in 4x4 except my missus' auto 03 grand vitara.

[nharv88]

jdk81 wrote:

Manufacturers make other vehicles similar to what you want.

suzuki gv
subaru Forester
prado etc

hi jdk81,

a forester isnt off road capable
prado is far too big
and the only suzuki constant 4wd i can find is a brand new vitara

[pezz]

When you say your wanting constant 4wd on road for traction,
this sounds like your going to drive it like you stole it.

why not get a street car, wrx or the like.... and run a stock powered sierra offroad

way less messing about, and one less 4wd on the road drawing unwanted attention

sense makes?

[buzbox]

Safe to presume your coming from a fast-ish road car background. ?

Now, when it comes to 4wd'ing, take the go fast idea, and swap them with things that make the car go slower.

Im not having a dig, but unless your into rallying / offroad racing, going slower is what offroading is all about. Twin turbo blah blah have their place, but not with the majority of the 4wd community.

[nharv88]

im contemplating swapping my 300awhp GTiR for a sierra. ive been in stock sierras and they rev their nuts off along the highway.
i do however like the torque of the H25A in the Grand Vitara. by the time i add cage, winch, axles etc the extra weight should work in nicer with the torque of the V6 but still be 500kg lighter than the Grand Vitara. i like small cars, therefore ive always wanted a sierra when i decided to go 4x4

[nharv88]

But on the other hand the G13B GTi motor would go nuts in the sierra. i just dont want to be doin more than 3k down the highway...

[henno]

nharv88 wrote:

i just dont want to be doin more than 3k down the highway...

Why not?

[Gwagensteve]

What did you do to lower the cruise RPM of your pulsar once you added power? Wait, you didn't? So why do you think you need to in a Sierra.

All due respect nharv88, but I think you're at the start of a long learning curve. By the time you rip all the running gear out of a Sierra and replace it with something different, you'll have lost the point of buying a sierra in the first place, which is a light, manoeuvrable, reliable, and simple car that's amazingly capable off road. If you want a high power constant 4WD road car with light off road ability, there are lots that already exist, but you could always turbo a 2.4 litre SWB GV.

Personally, I think constant 4WD cars are terrible to drive from a handling perspective, so I wouldn't bother building a car with so much power it required constant 4WD because the loss of handling finesse makes the whole car more frustrating, but that's irrelevant with a sierra, because regardless of constant 4WD or not, the suspension, steering, and ratio of sprung to unsprung weight (especially if you fit holux axles) will make the finished car dangerous to drive. Sierras handle just fine with 70hp. They are kind of OK with 31's and 100hp. Beyond that though, you're outdriving the chassis.

Also:

how are you going to adapt your gearbox to the H25? Which transfer case are you going to use that will allow an acceptable rear driveshaft angle and length? how will you get the H25 sump to clear the hilux axle housing at close to stock ride height? and most importantly, why would you do all this to have a car that's ineffective regardless of terrain?

I'm all for people doing things that are different, If you're going to do something different it should at least be effective.

If you REALLY want a road capable high power sierra, why not look at buying a wrecked 2.7 or 3.2 V6 NGV and grafting the suspension and driveline etc into a LWB sierra? at least then you'd have a chance of the thing driving properly on the road.

Just some thoughts.

PS I see you refer to the NCOP in relation to engine capacity. Have you referred to the NCOP for all the other areas of the car you will be modifying such as emissions (via the turbo) brakes, track width, rim size etc?

[nharv88]

with shortened axles and brakes that come with it the engine mod is legal.
put all the emissions gear from donor engine and emissions are fine.
every 4x4 is turbo these days, guessin the sierra is just too light for increased torque...

[Gwagensteve]

Wtf?

How will you prove your turbo h25 meets stock emissions? How will you retain all factory emissions control with an aftermarket turbo?

Which axles will you shorten from a h25 grand vitara to fit your sierra? Or do you mean hilux axles? Which hilux has a turbo h25?

Sorry, im not sure how many cars you've fabricated and approved for road use, but this is an epic project and I suggest most engineers would decline to approve it or request you consider the project an ICV, which would likely preclude using a sierra as the base vehicle due to age/lack of crash test data.

Good luck with the project. It's one thing to have an idea. Quite another to see it to fruition.

Steve.

[5ierra]

nharv88 wrote:

Hi everyone, been thinking bout a sierra build.

H25A V6
maybe twin gt2052r or GTR stock turbos
vitara gearbox
*or*
G13B Twincam with gt2052r turbo (best response from what i can figure)

prado (or other constant 4wd transfer)
hilux diffs
Disk brakes all round
31x10.5x15 tyres
15x7/8 sunraysias

i kinda have a feeling that is constant 4wd was doable it would have been done. thought it would be nice with the extra torque (i prefer traction to wheelspin)

i saw a couple of H25A conversions on here but never seem to finish it

Under NCOP we can legally fit a turbo 2.5L. dunno how it would drive, handle etc with the H25 but it is all aluminium

Right. So lets start at the beginning.

Id be interested to know how you intend to fit two turbos and a v6 in a sierra engine bay (assuming the Radiator is rear mounted like most h26 conversions are. Then you still have to fit an inter-cooler. Thats going to be a metric fuckload of ducting because its probably going in the back aswell.)

G13BB more attainable, but why would you spend $10,000 on a sierra engine, really... you will NEVER get your cash back and you can achieve better, more reliable torque through gearing.

Vit box is good. Auto or manual? Both a suitable. (With g16b's, not sure how they will go with the power you are wanting to put through them).

Constant 4x4 sounds horrible. Is it going to be a rally car? I know I would prefer the ability to crawl over constant 4x4 any day. Keep it simple, stay with a sierra case & 6.5's. Want strength, get a Sambox.

Hilux diffs for 31's? Thats a nice step backward. This will DECREASE your ground clearance as the centres are bigger, not to mention all the dead weight you are adding. You can run sierra diffs with 31's and make them nearly bullet proof if you drive the way you claim (not spinning wheels). Chromo front axles and cv's, floater rear.

With all that weight you are adding in the front you can also kiss articulation goodbye because of the beefy leaf packs you will need to keep the nose up will be stiff as shit.

You're also going to be very hard pressed to pass a lane change test, which is now required to be able to engineer the car in QLD. I also believe those little sierra brakes are probably going to struggle with that power. So that means Vitara vented brakes. Also means you will need 16's.

Sierras are meant to be little, nimble, agile underdogs. Thats what makes them awesome. What you are wanting to do is take absolutely everything that makes a sierra a "sierra", and replace it with something worse.

I commend you if you actually succeed but it wont be capable and every sierra thats been built using the tried and true methods will run circles around you offroad.

My2C

[greenzook89]

Notwithstanding all the above... I have a relative who has multiple cars.... He spends ALL his time building them and never enjoys them. by the time he has finished them he has lost the spark that made him want it in the first place. Thats not what a Sierra should be about. Whilst its great having a project and a unique car at the end of it, you would be pretty upset if you hit the tracks and a stock coily outwheeled you.

My Advice is get/build A Sierra with 30/31's, geared correctly, and if you want a bit more power, a G16B. It will be plenty of fun for whatever you want to point it at. You can get a feel for what 4x4 life is all about and enjoy camping/fishing/getting away.

Anyhow... we have a previous rides thread..... should post some pics of the GTiR

[vet 180]

Mate sounds like you would enjoy the car with a simple turbo g13 or g16 31's and decent suspension.

It will end up being just as fast on road (due to weight, weight distribution, and torque delivery), much better off-road (due to smaller axles and above) much easier to fabricated (due to space in the bay) and much simpler to repair ( due to off the shel parts)

Ever driven a 800kg car with 200whp? With this kind of weight there is such a thing as too much torque


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[jimmey]

Hey man!
Some people on this forum seem to be a little bit impatient with big dreams and beginners haha But we're all tryna say the same thing..
Sierras are small, light, capable cars, I would love to follow a build of the extent in which you are thinking, it'd be unique that's for sure!

I'd recommend that you buy your sierra first, find one with a g16a/b whacked in her would be a great find and see how you feel. If you feel like you'd still need a bigger brain and have dealt with her and seen her weaknesses and what not first hand, then go for it.
Generally the main things you've gotta think about when doing a convo in a sierra is engine bay size, even the tunnel and what not, let alone fitting the turbo and the inter cooler etc.

In a sentence; finding space is like gold in a sierra haha.

But, in answer to your original question:
I recon the turbo g13b, that'd be sweet haha.