Isuzu G-series Twin Cam

Hi all,

We run a TD Gemini Coupe in Speedway and want to get a bit
more competitive against the twin cam Lasers and Corollas..

We are limited to 1600cc , currently running stock G161 with Nikki
wondering if there is an Isuzu 1600 EFI twin cam or similar that will go straight in.

Thanks Paul

There are G161W twincams.
And I doubt that you will get one - they are rare as.
People use the later EFI 11/ or ZZ/R etc G180W or Piazza/117 G200W.

(9Nov2009: deleted "but not EFI. They were all carby." from the first line.)

Thanks for your reply,

Were they the twin cam engines used in the Isuzu 117 and also Bellet GTR..

Do you have any HP figures for them ? and do you know if the twin cam head fits on a SOHC G161 block ?

Unfortunately we are limited absolutely to 1600 for Junior Sedan Class

also wondering if any later Holden or Isuzu 1600 will mate up to the Gemini gearbox.

Cheers Paul

Would a 4XE1 from a Rodeo fit ?

Yep - the G161W was in the Isuzu 117 and Bellet GTR.

The twin cam head fits on OHV G161 blocks and probably the G-S SOHCs, but not the G-Z SOHCs a la Gemini, Rodeo, Jackarooo etc. But you need the twincam timing cases etc.

HP was 120HP (DIN) @ 6,400RPM, 14.5kg-m @ 5,000 RPM. CR = 10.3; max RPM = 7,000 (GT-R & 117).
(Info for 117 EC Coupe says same engine but with Bosch EFI; 130HP @ 6,600RPM; 15 kg-m @ 5,000 RPM)

Gearboxes are generally interchangeable EXCEPT:
Petrol G-W twincams, G-OHVs & G-S SOHCs have left side starters; G-Zs & 4Z series have RHS starters.
Some diesels also have LHS starters.
Early boxes are course spline in & out with 16mm ID spigot.
Later went to fine spline input shaft (with course drive shart).
Later to fine spline output.

Some fine-spline outputs are bigger diameter - eg auto & MUA boxes.
Some input shafts are 17mm spigot - eg MUA boxes, some DOHCs?.

Gemini MSG type boxes can have their bell swapped for a DOHC bell (ZZ/R Gemini etc).
The front layshaft bearing can be interchanged between early needle & later ball to suit.

MSG bells won't fit MUA boxes (ie, rears).
(MUAs came out with the 4ZE1 2.6L and later.)

So what have I stuffed up - the above really stretches my memory....

Can you add a turbo?
There was a well known fast GTR Bellett in Melbourne that "merely" had (allegedly) a standard G161Z with Garret T03 turbo - it was clocked at 149 MPH (234kph).

Some people would be tempted to bore a G180W to 2L, change an 8 to a 6, and use its standard 300Nm@2k RPM torque..... (nearly 400Nm@3kRPM).

I have no idea about 4Xs. Older G-OHVs, G-DOHCs, G-S and some 4Z, but not much about G-Zs and nothing about others.

Would you believe I spotted the basis of your new more competitive engine on eBay!!

http://cgi.ebay.com.au/Holden-Gemini-Ro ... 51053776QQ



This one has an early EFI setup that looks like it would be a tight fit in a Gemini but.... a starting point all the same. It will probably need a few things altered to get it in there.

get rid of the intake, unless u wanna belt the shock tower, change the oil filter mount then go for it!

i would love to drive a 1600 dohc, i am very familar with how the 180 and 200's go, but i reckon the 1600 would b a little screamer!

ps i got lots of dohc spares if u need help

cheers

Yeah, agree bloke. If I had a bit of cash to flash I'd be on the way to pick that up right now. Something about getting the best out of the least does it for me.

Back in my younger years when I worked at a place where they imported US iron, I still stuck by with the good old Holden Red in my EH. The fellas at work really bagged me for it too. Everyone there was fitting Chev small blocks and even big blocks but I stuck with a six. I made my EH stop well and handle well. I used custom K-Mac springs and sway bars with Koni adjustable oil shocks. Always had a thing for Koni. I replaced the whole EH brake system with an LX Torana 4 wheel disc brake system off a 6 cylinder Torana we bought for the yard. As soon as I saw it was discs all round I snapped up the brakes quick smart. Powered by an LC XU1 spec 173 red and it fkn HAMMERED!

I drove the boss home one evening and he was used to driving a 63 Pontiac Parissienne with an off it's tits 454. He refused to get in with me again!

I bought a Chev 302 which I built back to original specs and sold without even fitting it, without even running it!! They were easy sellers for top dollar prices. Too hard to find. I bought a brand new Chev 229 V6 4 bolt mains performance engine (Crate engine) with part of the money I got got the 302. That ended up in the EH with a Borg Warner T10 4 speed behind it. I ended up selling it all as parts after it got hit by some uninsured prick. I still have the T10 box and Hurst shifter.


Mate all I can say is go for it. You have the support of elky and trust me, he can probably find anything you need. If he can't I know IZU069 will know where it's hiding. Both of these fellas are rock solid Isuzu nuts. (lol)

It looks like a 117 engine (sump, and the non-integral intake manifold).

Probably 10.3 compression.
There were 120HP with carbs; the EFI 117 EC was 130HP.

Same oil filter as early G-OHVs (can be replaced by later version that takes up to a Z9 size filter).

Dizzy should be no problems (can fit Gemini dizzy with RB reluctor to drive any IgCoil).

Should be able to use G161-OHV block if desperate.
[Not sure about G161-S - the non-Z SOHC; I know the G180S block is the same as G200W (bores excepted).]
And also unsure of sump - on G150 & G161 OHVs, the Bellett (Gemini) and Florian (117) sumps were interchangeable assuming the matching oil-pump pickup....
And later G161Ws changed main "rope" seal for G161Z type rear.

I hope those details are correct - it was long long ago (in a shed far far way).
I still have a G161W block, but several other parts found better owners.

Sold.

I think for $325. (Cheap!)

A steal at that price.

I know of GT-R G161W that sold for much more than that recently, but that was an overseas buyer where they are into racing big time.
It's one of those situations - its rare and therefore worth heaps but old and select (like Florians & Piazzas LOL!). It needs the right buyer, and I get the impression Gem owners are like Bellett owners - the won't spend much (with a few exceptions).

PS - I think I should correct my above "G161 were carby only" eh?

For a speedway car I say build a serious G161Z. Port the hell out of the head, EFI it using a rodeo manifold. Have the head welded up for high compression (aim for 11:1) and run a giant cam, flycut the pistons if need be before assembly. Have the lower end balanced and make sure the whole setup's really free flowing. You could even try to fit a bigger throttle body out of a commode or something. Highcomp G161 + free revs + EFI = fast. More bang for buck than looking for a rare G161W! Would be cool though.