Isuzu G-series Twin Cam

Take 4 - well this is number 4 chevette - first chevette sedan, and in total my 7th 'T' Car.. (chevette hatch x3, gemini sedan x1, gemini wagon x2 - also wrecked two piazza's)
Well About time I posted up some photos..
Chevette, drooling oil, well more like raining but anyway... Plans...

So after lugging around this diff for around 1 & 1/2 months in the back of the wagon (how many of you can put a diff in the back of your car?) After stumbling awake at 3pm (was awake for 23 hours thanks to the girlfriend ), I decided pull it out and put it in..

Full nolathanes throughout, cheers to Prozac our friendly parts supplier, also for tig'n up the diff hat and giving it a lick of paint! I made new gaskets for it and assembled, also the ZZ/T diff was missing the input shaft, so I bought a complete torque tube and swapped it over..

Whats so special about this diff? well look closer and you see factory discs! Also must mention thanks to the old man, lent him the wagon (with diff in it, whilst I took a car trailer back for him) and he degreased and waterblasted the diff!

After putting the diff in, I had to make some small adjustments, mainly a extention of the brake hose, and redrilling the torque tube mounts around 15mm each side further inward

Have 1x G180W and 1x G200W at my disposal, both with gearbox's, loom ecu etc. Also know of another G200W..

Havent decided on whether to run the G180W or G200W as of yet, mate is trying to convince me to run a eaton supercharger too..

Have 13x8 Rostyles for the rears, I need to change springs slightly to get them to tuck in nicely without rubbing..

I bought a pair of extractors off elky here, which I plan on using, but more importantly, what other mods does anyone recommend for the twincams

I see alot of talk about Delco's?/Changing to a RB dizzy - niether are really that common in NZ..

Also I can confirm that a piazza front sway bar does not fit - is around 20mm either side too wide, so at the moment I've just got the chevette one in - may go uprated when time/funds allow

Chevette diff minus torque tube weighed a measly 53kg! half the exhaust broke off too (made the diff swap easier) so I took that with me to the scrap man for a total of 59kg, and profit of $8.70! paid for subway for lunch if nothing else!

Also clearance to the front spook/crossmember is just under the height of a redbull 250ml can

This is donating some parts... (Shaun ZZ/R was going to be using this, but has changed direction so now shall be mine )

Put my koni's in along with springs, sat quite nicely, then my friendly neighbourhood bogan (aka Bart) pushed it a bit further up the street, and into his driveway where I replaced the whole front end with nolathane once again, new balljoints, tierod ends etc etc.. Also bolted on the 13x7 Rostyles onto the 230mm piazza front discs..
Dragged it back down the street after having to put the bikkies back on the rear - had 3mm between rear guard and tire with the 13x8's (unlipped) before we bled the brakes, after having some load on the car, it settled onto the tire.
(Now fixed, have superlows king springs in the rear) Anyone with a keen eye may spot a couple of other differences, stainless aerial, and engelmann mirrors (came with the konis from germany) And a front spook I made up from a EP81 starlet

Also, scored whiteline adjustible panhard rod, nolathane sway bar mounts, steering coupler for $140 from good mate Prozac (works at repco, did have a GM/T project but needed the space)..

plan on using the original 1256cc fuel line for the return line, have bought some 5/16 steel line to bend & flare up for use. Got a 1.25l surge tank being made up. Scored myself a Camira fuel pump (looks exactly the same as a VL pump??) which I'll use for the supply line, now need to find a suitable lift pump - thinking subaru leone?

I've stuck to G200Ws mainly for their torque.
Although the G180Ws pull about the same power, I definitely love the torque of the G200W.

Take it easy on mods. I have seen so many G-Ws wrecked.
Sometimes they are wrecked merely because they are never finished - most seem to underestimate the cost of even a plain rebuild.
Others are wrecked because they think they are Celica motors or 16V heads etc.
And some are wrecked by shoddy workmanship - spun bearings, low oil pressure, seized pistons etc.

You are probably lucky - the best G-Ws are the Piazza G200W, and they come with an optic CAS dizzy similar to the (Jackaroo) 4ZE1 etc - not the "retarded" mechanical dizzy that GMH used in the Aussie 4ZC1-t Piazzas.

My original 117 G200W was converted to twin DCOE45s (because EFI was rare back then) and with minor exhaust mod, it had max torque of ~380Nm @ 3kRPM (ie double the standard torque at half the RPM). (I used a heavy-duty Rodeo clutch.)
The Webers took it to 135HP/100kW (rear wheel) from the standard 135HP flywheel.
I was intending to take it to 230HP (cams & a mild port) but that required forged pistons and I wasn't keen to spend. Besides, she was too powerful with the torque alone!
(But now I have a Piazza G200W with forged pistons.... But that will be EFI.)

With that as a basic build (with "standard" reliability), a turbo should take it to over 300HP without much effort. Though reliable 400HP turbo builds have been done. (I don't know the details, just the builder of GT Bellett that sold a couple of years ago with a ~390HP G200W turbo.)

I intend EFI next time. EFI should be able to duplicate Webers. I'm not sure if modern injectors have a better range - twin injectors were being used for performance G180/200Ws.


The better G-Ws are the Piazza G200Ws & the later ZZR G180Ws (apparently better than the earlier blue ZZR G180Ws).
The 117 G200Ws are okay.
The older green G180Ws had different (thinner?) rings and aren't as good as the blues.


Don't worry about the alternator - upgrade it to a later unit with inbuilt regulator.

And when the dizzy fails, do not repair it. Convert a Gemini (G161Z etc) dizzy and fit the RB guts.
If you use a Delco, use the Delco's HEI-8 etc ignitor, but fit that externally to a locked Gemini dizzy with RB reluctor pickup. The Camira, Astra, N13 etc Delco's do NOT use a CAS - they use merely use a reluctor dizzy albeit an crappier version than the RB (ie, 2-pole horizontal winding etc). (People are paying a fortune to have Civic, Camira and other reluctor grafts for no reason.)

Always keep G-W dizzy gears (on the bottom of the dizzy shaft), and gearbox bell-housings (they can be swapped with G-Z etc bellhousings/boxes).

Slight update, bent 5/16 fuel line up on sunday, pulled it out, flared the lines up, chassis's clipped it back in, looking lush.

Took fuel tank out, getting 5/16 inlet & outlet put in, hopefully ready tommorow!

See the extractors here and the modified engine mount Bart & I came up with, and more sweet arc welding from his old man. Bought some crackel paint off Prozac (along with a heap more parts & stuff) , paint stripped it, then repainted the cam cover..

Gearbox cross member , using original gearbox rubber. Just need to have plates for ontop of the floor and then thats done..

Bought these sweet porsche 911 recaros awhile back, degreased, fabric softened at work, in work time They're leather, recon it'd be worth buying some nugget and cleaning them up that way? trying to have a period highback look - dont want recaro fishnets or anything...

Wouldnt believe it unless you saw it yourself, but the chevette rails bolted straight onto the rear porsche seat mounts, the fronts were about 5mm diagonally out.. Drivers seat however had alot more work involved due to the electric adjusters..

Only really means anything to a chevette owner, but I removed the clock, mounted a amp guage, and decided I didnt like the dowel that was left from the clock, so I vacuum moulded a new lense up..

Inline filler neck, hiace top hose, Laser bottom hose, to volvo 240 radiator, with outlets swapped over..

Solex bonnet pins, front end painted after I'd dropped the block on the front panel, modified bonnet - After a fibreglass HSR bonnet if anyone is willing to sell ? (Front painted like a Kadett with the pinstripes)

Porsche 911 seats mounted, sliding properly. OMP wheel.. And a sweet badge I havent decided where to put it yet..

Fuel Pump mounted, filter mounted. Low pressure Facet pump - Can be found cheap/free in Subaru Leones.. (exactly the same as the aftermarket facet pumps on trademe)

Oh yea these... 40mm IDF's, rekitted, new throttle shafts & bearings, Trumpets just sitting on whilst bubblebath makes up the manifold

Also , driveshaft finally in, removed old fuel line, connect new fuel line up to pump setup, just the engine bay side to do now..

Similar to what we have here....

You still have the original "primitive" dizzy & alternator...
They are fine, but when they play up, replace the dizzy with a cut-down G-Z dizzy (Gemini/i-Mark, Rodeo, Jackaroo/Trooper etc) fitted with the FWD RB Gemini reluctor and the original dizzy's drive gear.
(I recommend the RB Gemini's blue ignition coil as well, unless you want to fit a high performance coil. The RB ignitor is current limited and even handles Bosch MEC717 & MEC723 coils (primaries are ~0.3 Ohms).)

Replace the alternator with a later alternator with inbuilt regulator. I like the Hitachi types - like LR170 (70A) off various vehicles - my latest being a (rare?) 3-wire Hitachi off the Subaru Legacy boxer - the 3rd "Sense" wire is taken direct to the battery no matter where it sits.


But an ammeter? Who the 'L uses those these days!!!
Replace it with a voltmeter. Pronto! (And bypass its cabling all together - its current should not run from the battery to the meter and then back to the alternator and to the vehicle's loads.)

(I can supply more detail on all the above.)


And are you tuning for hi-RPM power, or being clever and using what the G200W excels at - low down torque?
(My 300Nm@2kRPM & 383Nm@3kRPM cost a mere $200 exhaust, plus a twin DCOE45 set up on a standard engine.) Max engine efficiency at 3,000 RPM. (27mpg, ~10L/100km)

Pulsar dizzy cap & rotor, can also see modified slam panel with volvo 240 radiator fitted...

B&M oil cooler & fittings, hose care of Steve from Hydralink

Factory oil cooler supply & return lines...

Sitting waiting to be mounted properly.. Lines all connected

Oh well, I guess the ignitor matches the ammeter....

At least you get to use the cheaper early Isuzu (Bellett etc) dizzy cap & rotors...

Since this was just bumped by a short-lived spamster....

My comment above was directed at ancient technology - namely ammeters and DOHC dizzies.

For those still in the dark....

Ammeters are useless. And non-shunt ammeters are potentially a hazard. They also add to unreliability.
A voltmeter is not only safer and doesn't effect reliability, it also tells you if your alternator is over- or under-charging; if your battery is good, bad, flat, etc.
(Does anyone still use alternators with external regulators?)

The DOHC dizzies are much better replaced by the RG dizzy - ie, a RWD Gemini (T-series; G161Z or any G-Z) dizzy; optionally with the FWD RB Gemini dizzy's guts & ignition coil. (Warning: early RB, not late RB - they have a different mechanical speed advance mechanism.)
That not only supersedes the DOHC's seizure & wear prone multi-plate breaker plate with a cleanable reliable common bearing type breaker plate, it also uses a reliable robust and accurate single-pole reluctor trigger and a reliable self-protecting internal ignitor (if you don't want to feed a Delco or other EFI/EMS system).
The RB ignitor with its standard blue ignition coil has plenty of spark energy (I cold-started my G161-OHV with a battery voltage of 5.2V!!), but most ignition coils can be used without damage - I have used Bosch MEC-717 & MEC-723 which have about 1/4 the primary impedance (~0.3 - 0.4 Ohm).
The RG dizzy's shaft is merely cut (10mm below its collar); the collar removed and the DOHC drive gear substituted (with 0.15mm shim & a 4mm lock pin).
(Is there a Workshop submission for this yet?)

So had the bottom pulley ribs machined off and adapter made to fit Gilmer pully..
]http://i563.photobucket.com/albums/ss77 ... G_0491.jpg
Chromed the intakes
]http://i563.photobucket.com/albums/ss77 ... G_0489.jpg
Removed the old bonnet....
http://i563.photobucket.com/albums/ss77 ... G_0485.jpg
Trial fit of new bonnet
http://i563.photobucket.com/albums/ss77 ... G_0486.jpg
Big big thank you to Moosh for fibreglassing up holes & recess for slam panel - Great guy to talk to. Thanks to Alex yoeddynz for bringing the bonnet down!
Just got to sand & prep when some more shops open up...

So I bought the gaz adjustible shocks off Zep. Had them shortened 70mm to suit..
King springs, adjustible panhard rod ZZ/T gemini disc brake diff, all nolathane bushes throughout
http://i563.photobucket.com/albums/ss77 ... e003-1.jpg
http://i563.photobucket.com/albums/ss77 ... e002-1.jpg
http://i563.photobucket.com/albums/ss77 ... e004-1.jpg

So bought soft mounts, throttle wheel , good mate pete (valiant) made up throttle linkage for me.. Mounted them all up, just need to make throttle cable mount, and modify throttle cable..
http://i563.photobucket.com/albums/ss77 ... C00550.jpg

So moosh moulded a parcel tray/speaker pods up awhile ago for gemini's/chevette's. Took it into Wayne Patrick Auto Trimmers, who did a fantastic job covering it, went in for a 5min chat, left 40min later in work time. Races Pre65's and into his vauxhalls. Actually a real GC! http://i563.photobucket.com/albums/ss77 ... C00567.jpg

Finally arrived. Spent far too long removing one bolt from the trailing arm, was over sized and ceased in there.. removed the torque tube brake rotors and calipers, and wire brushed it all up, applied first coat of hammerite on it..

So been a long time no updates.

Got the car running with the help of Pete (Valiant) about 10 months ago, then spent the next 3 nights doing the full exhaust system.. On the friday I'd worked from 7.30 - 5.30 without any meal breaks flat stick at my old job. Decided I'd come home at the end of it and finish off the exhaust. Pete came around at 10.30 just as I was finishing up and convinced me I needed to take the car for a quick run - I was initially against it due to tiredness. Forgetting that way back when I first put the diff it the diff hat had had a small pin hole leak in it, which Zac had tig'd up, but then I'd never filled it with fresh oil afterward, which is fine when it'd only been pushed down the street to Barts or off a trailer into a garage..Diff locked solid about 2km into the test drive, at about 90kph...

Pulled the old diff out, and then pulled it to pieces...

I would say going by the broken bearings floating about, that the pinion bearing was starved of oil, which then ceased, as a result locked the pinion gear solid, but with the rotational force of the crown wheel, then spat the pinion clean in half and out the bottom of the carrier housing.


Wind the clock forward to present...
So the ZZ/R PF60 LSD diff arrived from japan through Ewan @ Hayatonka (very helpful and easy to deal with) finally. Got it home, sat for a couple of weeks till I got enthused enough to do something..




Sent away a pile of bolts, brackets etc to be plated by one Mr Greg Topp!

Came back and I'd assembled the diff with new bushes, painted it with hammerite, swapped calipers, discs, torque tube, brake lines etc all over. Also took the opportunity while the diff was out to underseal the rear guards completely..

Well been kinda busy with the house. Cleaned up the crossmember etc..

Changed a few things on the motor, whilst it was out, I was really disliking the VHT black paint that had flaked off badly. So sent the Headers into be HPC Coated.. Came up rather nicely indeed I think!

AT LAST - someone using a 4:2:1 exhaust to truly draw the performance out of (8 valve) G-W engines!

The 2:1 section looks a bit long, but that depends what it's been designed for... or, it'll be interesting to see its torque curve.

Bought it off elky, was meant to have come from a Rally car in Aus.

Ive gone 2 & 1/4 system throughout from memory (may be 2.5 but cant remember without measuring) with a straight through muffler and a triple pass as well, quietens it right up - can barely hear it over the induction when I had it going..

It's not the set I sold for the Brock-replica rally Gemini. That was far more mandrel bent (less welds) and its 2:1 was similar to mine - ie, ~26" for peak torque at 3kRPM.
I can't recall its ID at the flange but probably 2.5" because 2"-2.5" was ok and I wasn't prepared to complicate things with the "ideal" 4-4.5" system or whatever it was. (I ended up with 2".)

I was cursing I couldn't use my set, but those Gemini GW extractors were totally unsuitable for any Bellett, Wasp or Florian. They were the only GW extractors I had seen that probably matched and maybe exceeded the st'd (G200W) manifold performance.
Damned Z-engined Geminis! Why are they the "different" Isuzu (along with Bellett diffs)?

I wonder if yours will blue? (Unlike others, I liked blued headers. But I did not like blued discs & drums...)

The hpc should stay from what Ive read. Chroming will blue - I like the blue/golding on chrome though yes

The blue/gold is a temperature effect. I can't say I have often seen it on cars except for racers etc - not that I often see chromed extractors etc on cars due to brittleness, and racers or high-performance machines usually use black to radiate the heat better.

On bikes the brittleness isn't much of an issue (separate & supported headers as opposed to 4 into 2 or 1 welded conglomerations) and they typically have higher header temperatures (higher RPM; shorter chamber to header distance, and because bikes are often ridden harder).

Well, finally cracked onto doing a driveshaft loop, now there's not exactly much room in the Chevette's trans tunnel, especially once you put a larger gearbox and driveshaft in..

Can see nicks in the paint, it actually isnt rubbing, its from me test fitting 50 times..

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Filled the Gearbox with oil, tweaked a few things and then drove it out of the garage for the first time, resulting in this ;

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Nice. I was expecting some crunch...
(Sorry, is that a spoiler alert?)

What do you mean crunch?