Isuzu G-series Twin Cam

Kalmaker, 75rwkw in 1975 TX Coupe. Pics of engine in car to come. Finally after 2 years it lives!

Red graph is camira tune (stock tune which was on kalmaker at the time) green is tuned for my car.

Well, last week I had some trouble with the gem... I thought I had a bad tune on it as I had been experimenting, and it was running really poorly. After about the first 30 seconds of running it'd start running on 3 cylinders. I had It booked in with my mechanic to get a commodore alternator fitted as I wanted an upgrade and the gemi one looked to have a faulty regulator or something - charge volts were only 12.4.

Anyway I decided I couldnt miss my booking, plugged in my backup tune from a memcal that I keep in the glove box to get me out of trouble with my regular efi experiments, and it was still poor. with no other option I hit the road to my mechanic. Half way there the temp started climbing while I was waiting at the lights. When the lights went green It was just above the maximum end of normal. I pulled over, let it cool a bit, checked the coolant. None to be seen. Blah blah blah..

3 hours later I was back there with my trailer and decided to try a cool start. Turned the key and the engine just went 'ker-lunk" and wouldnt turn over. Turned out cylinder 3 was full of coolant and cylinder 4 was full of oil. Uhoh....

So this week my mission has been to get the head off and find out what happened - if It was just a gasket and the head was OK, or if I needed to find a new head or....?

This is what we found... coolant where it wasnt meant to be and a definate head gasket failure between cylinders 3&4. Apparently this is a common fault on g200w engines as there is not much between cyl 1&2 and 3&4.


http://www.justgemsofsa.net/forums/down ... php?id=858 <--- click here, these forums say max height for an image is 960px

So, we thought this wasnt too bad, and maybe the engine was good. We checked the head for damage, and found it to be fine. The rings and bores looked pretty good, and I decided that all was well enough that we could probably just clean it all up and use a VRS gasket set I had on hand, and put it back together. So some hours later (we did clean the valves up more after these were taken)...





http://www.justgemsofsa.net/forums/down ... php?id=862 <-- click here, tall image

Thanks to the timing diagrams on the twin cam forums, we got it all aligned properly. Shiny links and pully marks right at the top and the bottom, but note the camera angle makes the bottom look a fraction out... its not...

Interesting enough the shiny links seem to move across in relation to the pully marks as the engine turns but the crank and the cams stay in alignment with each other. After about 8? revolutions its all aligned as per the starting point again. As far as we can tell, this is normal.

The twin cam tensioner is a weird beast, its actually this thing here on the side of the front of the engine.

And it tensions the chain based on oil pressure. In order to set it, you need to push the shaft in until it locks and install it in the engine. When the engine turns it'll unlock and the shaft will extend and tension the chain, and lock at the point it needs to be at. Its shown here extended, and reset ready for install.

and so with another day of work getting everything hooked up again, we should be good to find out if its been a success!

Does the timing etc explain the lack of power (dyno) above?

I wonder if the headgasket was a Permaseal (V2032KC kits etc).
Many have said they are prone to failure. I measure OEM headgaskets to be a bit over ~20% wider between 1&2 and 3&4 (suggesting 50% added strength).

IZU069 wrote:Does the timing etc explain the lack of power (dyno) above?

I thought 75rwkw was a pretty reasonable figure. My mates got 80rwkw on his, so I think thats the ballpark for a standard efi setup on a standard g200w through a gemini 5 speed and drive train. How much do you expect?

I wonder if the headgasket was a Permaseal (V2032KC kits etc).
Many have said they are prone to failure. I measure OEM headgaskets to be a bit over ~20% wider between 1&2 and 3&4 (suggesting 50% added strength).

Yes it was, and the replacement is too. If you click the link between the pictures above (it was too tall for the forums to accept it as a displayable image) you can see the fresh gasket layed out on the block. It covers the space between the cylinders appropriately, so I'd say the proximity of the front two and rear two cylinders creates the problem, even if a better gasket will help. I saw today someone on ozgemini is doing a run of MLS gaskets (Thomas4parts) for the g180w and g200w so one of these would probably be a better option.

antus wrote:How much do you expect?

Oops - I'm so used to my standard 117 G200W which has about 20kW above yours (across the range).
That was with twin DCOE45s and EFI should exceed that.
But then again, I had a trick exhaust (and often a points dizzy LOL!).

I've since compared your dyno results to the 117 G200W output (std @ flywheel) - it tracks much the same with 40kW@2400RPM & 100kW@~6160RPM which seems reasonable for transmission losses.

My 117 G200W dyno results are a bit above the standard G200W but are atrw instead of the flywheel.

I ditched the twin DCOEs in favor of EFI for various reasons, but in part because I expect more from EFI.
But I have yet to do the calcs etc. Twin injectors were being used on the G-Ws (ie, G180W) as singles were inadequate - but that was over 10 years ago and things may have changed.

I realise now it would have been good to have done on mod at a time - I fitted the DCOEs (which were to boost power from 135 to 150HP) at the same time as the exhaust (which doubled the peak torque but at half the RPM - ie, over 300Nm@2kRPM etc).
I'm curious how much difference the DCOEs made....
At least now I have pistons so I can take a G200W to the next stage (230HP+)....

I was probably hoping for more from your Delco, but if the timing was out....
At least it looks like a standard engine - except for it blowing up (sort of) - it doesn't look as if anyone has wrecked (ie, modified) it yet. Lucky you!

What sort of intake are you running on yours? There must be some reason yours got those kind of numbers. What kind of dyno was it measured on? My engine and my mates engine are both standard, one on delco one on motec, are both within 5kw of each other at the wheels. I'd be interested to see what your AFRs are across the range with carbies. I have no reason to think my spark timing is out. I have since ported the tune from kalmaker sp3 to the free OSE12P delco software and the tune is in ballpark, but when the engine is good again I will be re-visiting it. Without intake mods I dont expect any difference.

It was the GTR(sic) replicas.
Nothing fancy - all was exactly as described/predicted - actually maybe a bit better once I figured flywheel from atrw). (I have described the setup numerous times - definitely on OzGem, I think hereon & maybe HolGem; Bell65 seemed familiar with it too (BellNet etc).)

One big advantage is that I could use the standard G200W exhaust manifold which most Gem's can't. It takes a good extractor to beat the original manifold.

Updated 13Feb10: As to AFRs, I was getting ~24-27mpg. (Apparently up to 10mpg better than the Wolfman's (green) G180W). /^d8

I can't remember the dyno type. It was done a Tate's - now gone, but they built race engines etc.
My tune was delayed because they had their dyno checked - they didn't believe the results they were getting. They never laughed at me again LOL.


BTW - timing - I thought you meant the cam timing was out.
Ignition timing can make a big difference (I've experienced 15%), but yours shouldn't be that bad - unless you use a timing light LOL! (Though those older reluctors aren't as good....)

Finished off the re-assembly last night after getting some fresh hoses, and it lives again!

http://www.youtube.com/watch?v=54v-X4A1DsY

You need to EQ that mic!
Or fit a low-pass filter....

Just got my head back from the engine shop.... I got to it before it was totally stuffed, but I had poor oil flow to the front exhaust cam and so the cam was damaged, as was the bearings there, and there was far too much play in the exhaust valves and one was just starting to leak. So, replacement cam, some more 2nd hand bearings (for now) and.....

hot wash
dismantle & inspect
replace camshaft rockers/buckets
bead blast
reface valves
k-line guides - exhaust only
cut valve seats & vac test - performance seats
mill head
line bore cam tunnels - exhaust only
groove cam journals for improved oil flow
set valve clearances - shim type
mild pocket port
R&R oil gallery plugs
clean & assemble

Looking forward to getting it back together The porting it quite mild, its pretty much just the back of the ports and the shoulder of the bend is gone. Its expected to flow about 10% better, and with all the valves working properly now it'll be interesting to see how much more power It'll be good for.

You're probably sick of this repeat, but the old build with DCOE45s was the exhaust mod (26" 2:1 after the stock manifold) for 150HP and the ~400Nm torque (ie, up from 135HP and double the torque at half the RPM).

The next stage involved engine mods - cam grind (with L1 profile for road use) and slight porting (only). That brought it up to 220-230HP, but forged pistons were required above 180HP. And heavier cams for racing and competition (I don't recall their output).

The above had the same reliability as the standard G200W, and great road economy with its peak torque at 3k RPM; 300Nm@2k RPM.
And it is quite close to the HDT G180W mods. The main "essential" being the DCOE F2 emulsion tubes (and probably cam profile after reading of other wasted cams - the G-Ws breath unlike any other engine!) apart from the standard exhaust manifold and suitable inlet manifolds (the 117 aka GTR replicas being the best). That assumes a $500 exhaust & cam mod + $1,000 (optional??) pistons + the Webers and manifolds.

Then there's the turbo option... (400HP, ditto reliability.)


I might put my Piazza G200W together (it has forged pistons, but unkown cams) with the exhaust mod but with a Delco for my Wasp while I replace the Wasp's main seals (I sold my DCOEs with manifolds and Gemini extractors). If so, it'll be interesting to compare performance considering EFI should outperform Webers, but that assumes suitable injectors (some G180Ws used twin injectors back in the 1990s) and maybe the extension of the Delco self-tune range (I might remap, but I won't pay for dyno tuning since self-learning does all that).


Good luck with yours. I just hope it doesn't have the same problems others seem to have after rebuilds (dog knows why!).

Well thanks for looking, but I dont think we should all build exactly the same package. I have a plan, know my next steps and its well on course. This is a streeter, and efi is better and its my hobby. My other gemini is the insane-o skyline GTR killer. This is my sleeper.



http://www.youtube.com/watch?v=iJFc6rdMv7E

Ah, but I like power!

And I too hate this 25char minimum, but it prompts me to write a more complete relpy.


I take it your on-track builts is merely a recondition.
As for not having the same rebuilds, I agree. But it perplexes me why people spend $thousands for performance increases less that what I have so often described.
Reading the things others have done pains me when I know it is an inferior yet more expensive solution.
As to the so-called unreliability of the twincams, what can I say - they aren't. But when you get silly things like crimping oil lined for greater oil pressure, not soap&watering hones, bigger or uncompensated injectors, wrong emulsion tubes, questionable rebuilds (by alleged experts or qualified people), other vehicle parts - and cams!, etc - it doesn't surprise me that pretty soon oil catch cans are added, or big-ends get spat out etc.
Cam bearing-shell wear I can understand, and rattly timing chains on early 117 G200Ws, but not broken chains or transmission (crank, conrod) issues.


I thought that DOUBLING my car's acceleration for about $1,000 ($200 (complete) exhaust refit, $270 manifolds, $450 carbies; plus filters etc) was a pretty god achievment.
And a 70% power increase for a futher $300 cam gind plus a DIY port job (else pay) is excellent - not that I was prepared to pay the (then) $1200 for forged pistons also IMO required.
Not many engines achieve that so simply and cheaply (except for well underperforming engines).

And not that I know how those mods work with the standard Jetronic EFI, but I changed to carbies because they were cheaper; the ECU was not supplied; and back then, remote EFI troubles could not be fixed. (Compare that to pulling into Gundagai some 5-10 years ago with Weber problems I couldn't solve (LOL - it was the 100-120psi compression that was the problem!), and they had no idea about carbies.)
Later I was going to fit my own EFI (based on an 68HC11 - same base as the Delcos) since reasonable aftermarket ECUs were simply too expensive ($2,000-$4,000) for IMO limited feartures. (Yep, electronics & digital was my hobby too along with cars & bikes.)


I do know that some like spending money for the mere sake of it and hobby rather than effective engine outputs. But in my experience this Marque has been populated by those less financially fortunate that still want the Gemini-type preformance that beat the supercars at Bathurst. Hence most of my posts - especially on inferior solutions like mating Camria/N13 dizzy tops etc (and CAS from Magnas etc when the CAS is not required).
But for those expense caveats I apologise - that is a hijack of your thread. I merely replied (without rereading the earlier posts) with my typical FYI - more for the benefit of noobs that may not be aware of previous information (this forum having been so quiet ).

So hence my description of the "basic build" for a G200W with ~400Nm & 220HP for economical street use.
It is merely a baseline for what other performance G-Ws should have- eg, G180Ws with the same power but less torque, etc. That's a build that has been around since Brock raced his G200W Gemini.
Plus that 390HP has been achieved reliably with a turbo.
I know of a na 370HP G180W, but that was by a Dandenong dude with unknown build (I don't recall if he was one of those "experts" that destroyed engines), and it was after $7,000 spend - I reckon I'd prefer the G200W 390HP turbo option.

IZU069 wrote:I take it your on-track builts is merely a recondition.

No... But its where im at. The head had quite some wear and needed the work it got. Now it should be solid for years to come. I could have put hot cams in it for NA, but that would not have suited boost, or turbo cams, which would have made it run shit until then.... but I dont want this thread to get too futuristic. I have been amassing parts, but between my mates and myself the racing season is starting and we have 3 track cars to work on as well as this one.. so all in good time.

Im not sure if you have admin privs on this forums, but if you do can I suggest a couple of forum config tweaks? Can you kill the 25 char post limit, and can you remove the maximum image size limit? The title of my thread mentions kalmaker, but the car is running OSE12P now and i'd like the title to reflect that. But I am getting errors about the image sizes in my first post when I go to save the changes to the title. Its not been running kalmaker since 2009. If you dont, do you know who to ask? poida? Is he still around or is this place running on autopilot?

Sounds good. BTW - my future is still Sept 2005. (Though that was recently shifted to Sept 2015...)

Alas I only have Spaminator admin privileges - I reckon Poida thinks I've been corrupted by OzFem and other ex-forums.

You should be able to re-edit your OP if you resize the pic appropriately, not that I know if that modifies the Topic title, though IMO being the OP it should, and most modern phpBBs (V3 etc) seem to function as they should (at fracken last!).

Otherwise under Administrators & Global Moderators, (bottom of the home page?) is Poida & Bradlze ranked as admins, and also Virtual-R but unranked. I'd expect any could change the Topic title direct...


But get Poida off his slack little arse. It's about time he did something useful.
[ Actually he recently saved this forum. An interesting situation that we both are somewhat knowledgeable and have forewarned (others) about, but from the little I saw, it seems the very professional handling by Poida and the site owners overcame the issue. But I'll leave that there - this might get moderated though!! ]