Hey fellas,

New member here but not-so-new to these engines [I'm one of the dreaded Gemini crew]. Although I have had one of these engines before all I did was tune/drive it and blow it up about 6months later After a brief hiatus with a turbo'd SOHC ive got my hands on another twin cam and am starting a full rebuild. What im trying to do is get all my eggs in the one basket so to speak - although I wont be starting on the engine for another month or so, i want to be able to source all the parts etc that I need first prior to starting.

So what ive got is a G180w ex-PF60E - front and down oil filter, later rocker cover version - in about 10,000 pieces atm. Initial inspection says I should be able to reuse the pistons and the bores can be honed-only. The following is a brief run down on what Ill be doing, followed by what I need some help with.

-Rebuild using G200z big ends and G180z/G200z main bearings
-G180z piston rings
-Headgasket reused as it looks fine and i know how hard these are to come by, especially a graphite one as this is
-Water pump etc all look like they are in reusable shape

Engine came sans-cams and gears [since sourced both], inlet manifold [will be making one so moot point] and distributor [will most likely be going CAS off the crank pulley]. Inlet will be 4 x 45mm throttle bodies [have these, ex-RB26 GTR] with the injectors placed as close to the butterfly as possible. Already have 4-1 extractors for it - just need to hope they clear the engine mounts - typical of DOHC-on-petrol-xmember-in-gem saga. Now, if your still with me after my incoherent rambling, the areas I much need assistance/clarification on are as follows:

-Cam grinds. Looking at getting the cams reground so a pointer towards specs or someone that knows these engines would be much appreciated. Being quite scarce, most people Ive spoken to have no idea about these engines so getting some good advice is proving difficult. What I would like is to enhance the power between 4000-7500rpm - dont really want to go over 8000rpm as the gearing becomes an issue. Those that know Geminis well know that its virtually impossible to change the final drive in the diff short of going an all out diff conversion. Ive been told to look at 2TG's and 18RG's for cam grind/spec ideas, but knowing how crap Toyo engines are and seeing as most Toyo owners, particularly stateside are chequebook warriors [ie they order the parts and dont know jack about the specs] im finding this difficult too.

-The head itself. I know these flow alot better then the SOHC one, and they work alot better then the specs suggest. Are there any real hinderances/restrictions and should I look at getting it ported? Ie - do they have a design flaw that causes them to run out of breath at anything over 100rwkw. I suppose i could measure the valves easily enough, but are they the same as the big-port G series SOHC?

-Cam bearings look serviceable/reuseable so they should be ok, especially considering I cant find new ones. Is there a source for these that im just too stupid to find? Also, whats the go with the valve seal/brass-ish looking collet? Anywhere these can be found? Havent checked to see if it actually IS leaking past the valves but replacing these items would be just common sense.

-Timing chains. Obiouvsly there are two sets, am i right to assume the lower chain [crank to dummy/pushrod cam] is the same as the pushrod G series ex-Bellett? According to this -> viewtopic.php?f=40&t=1446 , that would mean I want 5114 038 or S114 098, to suit a Hillman? Saw this on one of the build threads:



Does anyone have more info on this? Id assume 'that' Mitsu engine would be the Astron as these run a double row chain as per dohcs.

-Pistons. I know G series SOHC's can be dropped in however these would lower the CR which is not what Im after. Have heard rumours of toyo 2T pistons being able to be dropped in. Not sure if these were the 2TC or 2TG items - old mates memory was abit how-ya-goin. Any ideas as to wether this is doable [can still get 2T pistons aftermarket, same cant be said for the Isuzu DOHCS] or if there are any alternatives? Abit of a bump in CR wouldnt go astray.

-Inlet flanges. Anyone know anyone making these up?

Think thats about it although there will most likely be more. As an iside heres the last DOHC i had:



Was a bone-standard G200w that I modified to take a VN-S V6 throttle body, also had crap 4-2-1 extractors [trust me, they were attrocious] and an as-old-as-time-itself Haltech E6K Ecu. Made 82rwkw which was enough to send S2000's home!

Hi ?

welcome to the the group

Although I have had a couple of DOHC's Bellett's in the past, I can't help much if at all on the specs of cams and the like. Mine were stock.
Pistons etc are a problem if you want to maintain CR or boost it. Rings should be easy to get though.
At the time I had a 1800 DOHC (long time ago now) chains were easy to get made up.
I think at the time I used bucket shims from a Toyota.

There is though a set of gaskets currently on ebay which might be of interest.
http://www.ebay.com.au/itm/ISUZU-G200W-DOHC-FULL-GASKET-SET-PIAZZA-HOLDEN-GEMINI-G200-TWIN-CAM-/261018545307?pt=AU_Car_Parts_Accessories&hash=item3cc5eaec9b

There are a couple of members here with current builds of the DOHC who can probably help much more thn me.

My understand ing of Gemini rear end is that is that it's basically a cut down Commodore and many parts interchange, so i assume gears also.

glenn

vrs kits are available from bursons, rings and bearings are same as gemini. I can give you part numbers for the timing chains i used but you need to take a couple of links out.
Looking at the head there is not a lot of meat there for bigger valves We have had to use second hand parts in the past 1 engine needed a piston the other needed a inlet valve. Being a gemini man i would assume you know or know of elky he has supplied second hand bits in the past. To my knowledge cam bearings are not available be carefull with them. Sump gaskets are hard to find also but you gan get around this or buy the set that Glenn speaks of. There is a gasket that goes between the head and the timing cover be carefull with this one also it has to compressed with the head gasket so thickness is important.
The guy's that did the head up set the valve clearance the same as 18rgu.

Sorry Glen, it appears i forgot to sign off at the bottom



Yes and no, the Salisbury rear end in later models is based off the 6cyl VB commodores however it utilizes a torque tube which makes the pinion different to the Commo ones. Regardless - Commo ratios are actually lower [numerically] then the Gem. Gem runs a 3.89, if i were to increase the revs to 8k and over id need a 4.11.

GT Orphanage - im aware of the rings and bearings being the same/interchangable depending on model. One thing I did find out was that the rods have the second oiling hole on G180/G200w's that only the G200z has. When i mentioned the head i wasnt referring to going bigger valves, i meant more in terms of finding a new replacement. Isuzu seemed to be the king of interchangability between its engines so im hoping the valves are the same as I have a brand new set of 34mm exhaust valves sitting on the shelf.

I had heard of the VRS kits being availible from Bursons however I was told they were NLA and have been NLA for a while? If they are back id happily go and order a set. The sump-gasket ive been told by a friend that had one was to use a SOHC gasket, cut and glued together. Will have to check this, should have a spare sohc one floating around somewhere.



That would be good mate, along with any other related info [ie tensioner] that you might have.

Cheers,

Nick

Nick i bought 3 vrs kits last month so they are still around, I will have to find the docket for the chains.

Didnt know that, thanks for the heads up!

Cheers,

Nick-

Had a quick chat with Bursons in cambelfield....apparently theres nothing on the system for a VRS to suit the DOHC's. gt orphanage whered you get them from? Ive seen one set on ebay....but it seems abit steep.

Anyone else able to add anything to this?

I tried Bursons here in Vic also a few mths back with no luck either. But you need the exact part number i suspect.

The price on ebay though is actually not bad. Importing out of Japan if you can find one, will be a bout the same.

I recently bought a SOHC Bellett engine head gasket from USA for $8 plus $16 frieght. But not seen any DOHC stuff there.

glenn

just in case you think i am F.O.S.
I spoke to Adam at morayfield store and he said they are still available if you have drama's he is expecting your call 07 54993533 he said they get them out of vic [that big victorian wharehouse].

Glenn, unfortunately the yanks never got the DOHC stuff which is a shame as I have a few contacts over there...wouldve made getting some bits relatively painless!



Eyeyeyeyeye never called you FOS Thanks for that Ill be giving him a call tomorrow. Typical of bursons, absolutely useless! Had a decent arguement with one of the managers last time after they tried to pull one on my Mrs, i wasnt really impressed. Funny that....the manufacturer of the gaskets is actually around the corner from me! One thing I am curious about though....looks like theres valve stem seals in the pack? I always thought the DOHC's had a bronze/brass guide that did the sealing. See below.

http://blog-imgs-46.fc2.com/o/u/t/outli ... CN6376.jpg

Had a very productive day at work....for the gemini atleast Was talking to one of our dealers when i realised he also runs an Isuzu dealership Had a chat with him about it, he promised to pass on the details to his "go to" man in his service department. Mentioned this to our receptionist at work, the name Phil Brock came up [the ZZ/R Gemini he raced at bathurst] when our lovel accountant Dina piped up and mentioned she does his book keeping!

Spent half an hour with Phil on the phone [actually a really good bloke] and hes pointed me in the direction of Bruce Garland [another big name] and said I should get a hold of him....so thats the avenue im going down now. In the meantime I got a call back from our dealers "go to" Darrin whos going to work on a few contacts and see what he can come up with. Looking positive atm.

Cheers fellas, and gt orphanage....major thanks for the part numbers!

Nick

and there's more, quick phn call here to local Bursons.

V2032KC VRS set for G200Z as above.

They are available at Cost of $204.25 + $12 freight charge.

Call to local burons again, gave them the part number - what engine is it for? Errr i dont know. Just got off the phone to AAA Gaskets and your right it does exist sooooo going to order one now.

told ya i was not F.O.S This time anyway.
BTW i have been paying $135.99 plus gst trade there is room to move

timing chain i used are from bursons too
maxtop 3dr124 124links
maxtop 3dr60/06b-2#60l. 60links
i assume you know how the marks work on the isuzu dohc we put the joiner between the cams.

I'm guessing those chains will be same pitch as the SOHC engine also then. I have a full set of chains and gaskets for a SOHC here, just in case.

glenn

one would think so

DOHC is double row SOHC is single row - by SOHC i mean G---Z series engines. Id assume the lower chain [crank to dummy cam] is the same as the pushrod version, top one being exclusive to the DOHC only?

gt the chains you listed, do they need links removed or are they a straight go-er? Ive seen the 'diagram' [i assume you mean the paint-drawn jpeg floating around the internet thats apparently not for use without permission ].

trust me....
that bursons kit is for a W series DOHC, not a Z series SOHC.
the listing on their system is wrong, and that's why when u go in and ask for an "Isuzu G200W DOHC" anything, it doesn't show up....

I used Greg's part number with Burton's letterhead on it a few days ago. It's no longer available.

Hey Glenn, there was only one left after i bought mine from memory so im not suprised. There is however someone selling a full gasket kit on ebay to suit these engines - however, at roughly $400ish she aint cheap.

After long delays with getting the car painted, buying a house, getting ready to put a different engine [turbo sohc] in only to find out it was a dud, were back to building the twin cam. Have cam grind specs availible, will just need to get them ground