Isuzu G-series Twin Cam

hi guys im new

ive bought my first gemini.
it has a turbo twin cam in it but i dont know what it is.
im not real clued up on cars but it looks like the motor up top of the page with a pipe going from the turbo to a radidtor at the front then to the carbys or something like that.

the guy i bought it off told me its a 2lt with a gt35/40r and haltech what ever the fook that means. sorry
its a 1978 td if that makes any sence.
i bought it regested but the young fella said something about i should get paperwork from dot to say what motor is in there.
he told me it would be easy as and would of done it himself but didnt have the time as his misses was just about to give brith.

i think there is a slight problem with it and i mite take it to the mechics tho cause everytime i put my right foot down it bogs down then revs really hard and starts to miss ( like pops out the exuast)maybe it needs plugs or something . i think the clutch mite slip too.
do you know how much it should cost me for someone to go over the car and tell me whats wrong with it.
i payed $3000 for it is that good cause it looks really nice.

sorry for the long post guys

thanks alot

chuck some pictures up and we can start explaining what all the bits are. also where are you located. i think most mechanics wouldn't know what the motor is or rip you off after seeing you don't know much about cars.

Mate i don't know anything about turbo's but if he didn't give you the paper work with the car i'd say you'll have to get it engineered which will cost you a few $$$. But good luck with it it sounds pretty reasonable to me provided fixing the motor doesn't cost to much

sorry guys
i dont own a camara.
ill call a mate today and get him to look at the car hes pretty good with cars

Does it look anything like this eBayItem170271437945 (BellettGTwithG200Wturbo)?

That's a G200W 2L twincam fitted with turbo. Turbos were never standard issue with G-series twincams.
Other twincams look similar. The cam-cover varied with engine capacity (if standard) - eg red = G200W, bright blue = G180 (Gemini ZZR etc), lightish green = older G180W, others (dark green, black etc) were usually G161W.

G denotes Isuzu engine series (from 1960s to 1980s). W denotes twincam. And the number denotes capacity (161 = 1600, 180 = 1800, 200 = 2,000).

The front-left of the engine block (behind the alternator) should have a cast with G200, G180 etc (about 50mm high).

I've gotta say, if it really is a Gemini twincam turbo, and it's not engineered or running right, you pretty much have three options:

1. Start learning. A LOT!
2. Sell the car or parts, and run a simpler setup.
3. Spend lots on getting someone else to do it.

I don't know that individual turbo but GT35/40R sounds huge for a small 1.8 or 2lt engine. Haltech is good, it means chances are it can be tuned. If it's running like crap, chances are it needs a proper dyno tune, unless the last owner had one recently and it has started running crap since, in which case yes, I'd advise to change plugs, leads, perhaps even coil/fuel pump.

Getting just a twincam engineered isn't hard (at least in SA, not sure on other states) but twincam turbo with aftermarket ECU (Engine Control Unit or "computer" - the Haltech) will be MUCH harder and more expensive, that's if it's possible.

Unfortunately if you don't get things engineered you run the risk of being defected or recieving a canary/roadworthy from a police officer and not being able to drive the car until you get it "fixed".

Which state are you in?

hey guys
a bit of an update

had a mates mech look at the gem and all looks good.
the problem i had with the boging down and clutch he said its because its a big turbo it takes time to get to 20psi and its the wheel spining not the clutch. he said its an open wheel diff so it will only spin 1 not 2. ( is that right?)

also he told me a few little things that i need to do to get it blue plated to make it legal on the road. ( the bigest thing was it needs a unleaded fuel filler.)

he also booked the car in for a dyno tune on a one of his mates dynos for next friday just to check everything. lets hope its all good and dont cost to much.

the top of the motor is siliver and has isuzu on it but at the back of it there is some scratches and its red underneth.

im real happy cause i was hoping to get away without spending more then $5000 all up and so far its only cost $3500.

the mech said he mite be interested in buying it off me for a fair bit more than i paid as he is looking for a drag car for his work. but im not sure if i should let it go. he said he was looking at spending $6000 maybe more lol.

ah well sorry for the dribble ill let you know how the dyno goes.
cheers guys

I fail to see why it needs an unleaded fuel filler, but maybe he knows where you can get leaded fuel?
But if the original Gem had it, then it's ADRs etc.
But it shouldn't be required for the G200W.

your right IZU069 the fuel filler doesn't need to be changed since leaded fuel doesn't exist in petrol stations.

he said because of diesel fuel pump are the same size as leaded.
also need a breather for the fuel tank to stop it pressurising.
he will be doing it all so i know he will be happy with the outcome.
and i wont have to do it twice

gems have a breather for the tank dude, unless u got a different tank of course

if the lines are not hooked up right it will pressurise too

cheers

bit of an update.

got the car dynoed and all seems well.
on the first run it pulled 260 odd hp but the bloke wasnt happy with the tune he said it was to fat.
so after about 40mins of tuning they gave it to it again and it pulled 290hp odd befor the intercooler hose blew off.
so the replaced all the hose clamps with super clamps and put a 2 stage boost controler in cause they said my adjustable one was spiking
and on its third and final run on 20psi it pulled just over 300hp.

it got to tunes in it one at 8psi which is good for general driving to and from work and one at 20psi which is just out of control it just smokes the tyres even in 5th.

he was telling me that i really need to get a lsd or locker if i ever wanted to get grip.
he said there is a commodore lsd that fits in with little work, he use to run one in his gemini race car that he use to own. but he said there really rare he also said there is a locker that you can get new.

all up after 2 hrs on the dyno and all the shit he replaced it cost me $700 but $400 of that was the boost controler
it goes in on weds to get everything sorted for the mod plate.

cheers guys

can anyone help me with the info on a lsd or locker ??????

Glad to see it pull something decent!
I've read of a few turbo (or big spend) G200Ws than only manage a pathetic 200HP or so. And yours is G180W. Great!
(Maybe I should have bought that 380HP NA G180W for $7k years ago!)

The Commodore diff seems the way to go. There should be info on HoldenGemini.Net, else OzGemini. It is "a particualar diff", not just any Commode diff.

I don't think there are any air-lockers or similar that would suit.

the lsd he is talking about is out of the small salisbury in a wb ute cost about 500-1000 and you will blow it to bits.
what you need to do is get a romac 28 spline full spool less than $400 and a couple of shortened commodore axles and you'll have a very strong diff but it will be locked so you'll have traction but its not legal. then you add a strengthened torque tube from the guys on www.ozgemini.com $150 and you'll be sorted then. this setup is good for 9sec quarter mile.

That price is pretty good for the dyno tuning especially given the new part required. Any chance you could scan the dyno readout (libraries have scanners usually if you don't have one)? I want to see what the spool time was like. Must have sounded awesome, wish you had a video...

Yeah you definitely need a locked or limited slip diff. And wide, good quality tyres on wide rims.

Locked diffs are comparatively dodgy, LSDs are way better especially day to day, but they're also way more expensive. BAD44U beat me to it on the bolt in Commodore LSDs, they're rare as rocking horse sh*t, will need a rebuild and will probably meet a sticky end in tiny pieces with your setup. That said, the standard diff centre probably will too!

The two most popular options for LSDs in Geminis both involve a lot of custom work, and cost a lot of money. They are:

-Shortened live-axle (non-IRS) Commodore LSD, out of the various SS commodores etc, will need axles shortened, custom mounts, possibly custom trailing arms, custom tailshaft, custom brakes/hubs or run commodore stud pattern

-Toyota G series diff, live axle, best sourced out of an RN20-RN27 Hilux as the width is nearly right and it may not need shortening, but also available in up to RN40 Hilux's and will just require more shortening. There are heaps of aftermarket LSD centres that are still made new, and bolt into these diffs, as they bolt swap with cars like Soarers, Supras, etc so Japanese companies make the bits for them.

But yeah, I won't go into it more, there are like 20-page write ups on each in the OzGemini tech section. It's something you'd probably have to take to a metal fabrication/engineering garage, if you supplied the donor diff, the centre you want to use, any brakes you may want to change, and $1000-$2500, you could probably get it all done. It's a big thing to undertake but well worth it if you want an awesome end result.

or you get a rare jap spec zz/r lsd disc brake diff

i am gettin another shortly

did anyone say rocking horse poo?

cheers

hey elky have the zzr diffs got different ratios. nut161 said he had 4.3:1 in his. id be very interested in a set of these.

ZZ/Rs were usually a 3.583 diff.
AndI certainly would not expect them to be higher than a standard Gem (3.9?) - they were twincams afterall!

mine is 3.9

IZU069 wrote:ZZ/Rs were usually a 3.583 diff.
AndI certainly would not expect them to be higher than a standard Gem (3.9?) - they were twincams afterall!

where did you get the 3.5 from?

diesel were 3.58 and are the same housing but i can most def tell you they were ALL 3.9 no if or but's period...

yes there have been higher ratio's but these were made by either aftermarket mobs or the offical isuzu endorsed japanese tuner mob but i forget their name

As far as i know no ZZ ever left the factory with anything other than a 3.9

and i have pretty muck all the jap sales brohcures

cheers

Elky,
The 3.583 comes from World Cars 1984 & 1985.

The ZZR (& ZZT) (130hp; 2 & 4 door) is the "same as LD, LS & LT 100hp except (as denoted".
ZZR/ZZT list all different gears, but no final drive. The LD/LS/LT states 3.583.

hahaha

they are wrong

i got the diffs and brohcures to prove it

always take net info with a grain of salt dude

You know me - I never take net answers.

But this is hardcopy. And it's an easy thing to miss - that's where space saving can be a problem.

Funny how people find misinformation as humorous. Maybe I should start to laugh a bit more? But there are so many dikheds and so much bullshit on the web that I wouldn't be able to type!

EG - Audio expert: Rule #3 - Avoid earth loops. Rule #7 - you do NOT have to use the same earth point. (Noting that he doesn't mention earthless coax or interconnections.) Or voltmeters "taking heavy power" into cockpits etc. Or throttle assemblies before long pipes and bends.

ah touche!