Isuzu G-series Twin Cam

Hey I'm looking at rebuilding my G180W and I'm in need of help.

What do I do? ... Or is there a book/website I should read up on?

Oh and, heaslipauto on Just Gems of SA (Heaslip Auto) say they could enquire about how much it would cost to have cam bearings made - but he needs to know the size of the bearings. This could be useful for a lot of people so information would be appreciated.

Someone is already ahead of you...

http://turing.une.edu.au/~ashley/gemini ... c.php?t=95

Rod bearings - G series SOHC

Crank bearings - G series SOHC

Dummy cam bearings - G150/160 Pushrod engine [Bellet]

Someone correct if the above are wrong. Building a G180/200 DOHC is the same as building any other engine with the exception of torque settings and setting the timing chain up. Theres abit of info on this around.

Nick-

Cheers Nick. I wonder if it'd work to remove the mech. pump and replace it with an electronic one which drives through a filter? Maybe via an external line and welding up the existing one, or by modifying the existing one to use an electronic pump..?

I don't have the best understanding of how the oil system works, but I've read that thread and it has helped a lot.

A larger pump is definitely the go, however I have reservatiuons about the longevity of the drive gears on the dummy cam dealing with the extra load. For this reason I have made special mention of external oil pumps or dry sumping.

Are the cam bearings just the sleeve and brace things? I was expecting ball bearings for some reason, shows I've pulled apart plenty of engines in my time . They're looking alright, only a few minor surface scratches, nothing deep. I can get pics up sometime maybe. How bad is bad?

Just a quick q.

Which way does the dizzy spin on the w motor? Is it the same as the z series anticlockwise?

Does anyone have advance curve info for the stock dizzy (non cas/itec).
Also the cam timing/duration.

Lastly; are their replacement valves off the shelf with little to no mods required to make them fit.

I don't have my head here, its at the shop being machined up. I need the specs the get the other stuff done. Any help would be great.

Couped Up wrote:Just a quick q.

Which way does the dizzy spin on the w motor? Is it the same as the z series anticlockwise?
***
Lastly; are their replacement valves off the shelf with little to no mods required to make them fit.

Pretty sure the dizzy spins clockwise as you look into it, when you take the cap off. My engine isn't running but this is what my eyes and logic are telling me. You can safely assume that there are no off-the-shelf parts for the twincam engines, unless otherwise specified. I don't know about valves but I'd guess not.

I have just made a discovery.

G180Z rod big end bearings fit G180W, however the upper (piston crown) side bearing shell should not be interchanged. The oil hole in the rod which "splashes" oil onto the piston (this is my understanding of it?) is blocked up by the SOHC bearings, and the recessed path leading to the hole isn't there either.

Of course because it's a fit they can still be used but I'm personally leaving that half of the bearings as they are because they're not that bad, and possibly taking the new ones to a bearing shop to see what they think. The old bearing upper halves read "T9J STD".

I don't have a camera so I can't take photos but I'll see if I can draw something up in paint to show my point.

Sorry if it's not that clear...

Good observation.

If you were to use the Z bearing there is a good chance it will starve the oil supply to the journal if there is too much overlap to reduce the oil flow. Looking at the drawings it seems that the hole is far enough away to completely cover the drilling so no oil would flow at all.

I wonder if the answer would be to buy two sets of G180Z bearings and discard the drilled ones. Use the second undrilled set to get them modified so they match the original G180W engine bearing shell. That should work providing both bearing halves are exactly the same radius.

Both sides of the Z bearings have the holes drilled in them (ACL anyway, even though the holes aren't used), so two sets wouldn't help. Unfortunately it completely blocks off the oil supply hole.

I was thinking that they may be able to be modified despite the existing hole... It's hard to explain over the internet, I'll try to find someone with a camera, but the existing hole shouldn't cause any problems when machined over.

I wonder who, if anyone, would have the equipment and know-how to machine it in such a way? I'll see if I can find a bearings specialist shop...

Theres a couple of options here in my eyes.

Its possible that the SOHC top bearing shell can be ran WITHOUT impeding any form of oil flow. Keep in mind that the G161z and G180z only use the lower bearing shell as an oil feed - the G200z uses the top. Theres a possibility that the G200z bearings may be the same as the G180/200 DOHC engines.

Also, it may be possible to use G180z rods with the single oil feed, and thus G180z SOHC bearings as well.

Nick-

Would it totally mince the bearing shell if I had a hole drilled in it? lol

If anyone has some G200Z bearings lying around I'd be interested to know their measurement to compare to the G180Z's.

The diameter of the shell is the same, the only thing you should be worried about is the differences between the bearing.

Worst case scenario eli and youll need SOHC rods. Not the end of the world.

Nick-

Yeah I spose. I just see the twincam rods as superior items

*smacks you over the head*

They are the same you idiot. lol

lol

I thought the twincam rods were forged not cast or something, or that they were at least meatier and stronger. I'm guessing the oil feed line in the SOHC rods would do the same thing as in DOHC?

Methinks I'll just leave the upper bearing shells, if I get bearing noise I'll change em and see if I notice any difference in performance/noise/etc which could indicate problems - and I'm sure I won't. That said if I see some SOHC rods and they're just as tough I'll be sure to grab em.

I wouldn't mind trying to figure out a better way, if anyone has ideas I'd be happy to do a bit of running around with my bearing shells, but for my own cause it doesn't matter hugely, it's not gonna keep my enigne from running. Thanks for the suggestions though!

Right, I had a look at some G200Z rod bearings, they look spot on. Unfortunately I couldn't try em.

I know I keep asking but could anyone give me torque settings for crank, rod big ends, and cams?

Same as SOHC dude. When i get the rebuild book for the G200z im building ill pass the details onto you.

It makes sence that the G180/200 DOHC rods would be the same as the G200z bearings, extra oiling hole no doubt needed for the higher RPM these engines would see.

That said, the G series engines in standard form are a well-oiled little thing. Ive ran mine LOW on oil for about 2weeks [clapped out G161], revved the bloody things titts off everywhere and theres still no sign of bearing noise.

Nick-

Thanks Nick

Yeah, confirming, the G200Z rod bearings fit fine.