Twincam bellhousing quick question

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archangel62
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Twincam bellhousing quick question

Post by archangel62 »

Ok so I have a "twincam 5spd" but half the bolt holes don't match my "twincam sandwich plate."

I'm in the process of buying a confirmed twincam bellhousing to replace the one on my 5spd with, but I need to know... Do I only need the front half of the bellhousing up to where the gearbox turns "square" (the end of the clutch chamber)? Or do I need the whole bellhousing?

And also does anyone know if the two lower braces that go from the engine to the bottom of the gearbox are the same as G161Z/G200Z?

Thanks,
Eli
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Turbocoupe75
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Post by Turbocoupe75 »

The Gemini gear box housing is a two piece item, if you want to change the bell housing you need to split the gear box in 1/2 and change the whole front half over. I have had this done once, cost $100.

Why do you need to change the bell housing over?

The two lower mounts / braces should be the same.

See the front 1/2 of the gear box!

Image

Image
#Turbocoupe75
IZU069

Re: Twincam bellhousing quick question

Post by IZU069 »

archangel62 wrote:I have a "twincam 5spd" but half the bolt holes don't match my "twincam sandwich plate".
Eh?
What are you calling the sandwich plate - not the engine backing plate?

The bell housing is the entire front section off the box.
You have the bell, the sandwich plate (that carries all the shafts with gears, selectors etc), and the rear box section.

They are all the same sandwich pattern (unless you have a later MUA box etc from 4ZE1s etc).

Just unbolt the bell and refit the new bell (ater replacing the front seal). That assumes you have the right front plate that caries the clutch throwout bearing and mounts its pivot pin. Otherwise change the layshaft bearing to suit (ball or needle; ball is later/stronger).
archangel62
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Re: Twincam bellhousing quick question

Post by archangel62 »

I was told the big black plate between gbox and engine was the "sandwich plate."

Basically my supposed "twincam gearbox" won't bolt up right to my G180W's black plate thingy, so I'm after a different bellhousing.

I think I've learnt what I need to - I only need the front half of the gearbox casing/bellhousing. Excellent, less postage. So the back half of the gearbox is the same on twincams?
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IZU069

Post by IZU069 »

Well it is a sandwich plate I suppose, but I've always used engine backing plate to avoid confusion. And that's only a sandwich plate if the gearbox is on, but even then I'd use "flange" or similar (since it's an interface).

I'm wondering what backing plate you have then - it's not for an auto? (I assume they are different.)

Some bolts can vary in location though I don't think I've struck major problems. Someone once said some Rodeo boxes were a bit out (compared to Belletts etc).

As to the lower braces - I never use them. I think some were different, but that might be RHS vs LHS starter variants.

I'll try to get the Wasp horny tomorrow. Whilst underneath, I'll check hole alignment (even though she usually takes care of that) - I just hope she doesn't squirt in my eyes first. Maybe my diver's mask. Maybe the snorkel too - she hasn't washed for a while. (Only every Christmas whether she needs it or not. She didn't even wash off that kinky parrot poo from the 2nd last VicGem meeting. Damn copraphages!

AFAIK, there is only one pattern for DOHC bell bolts (MSG boxes) excluding maybe a few exceptions.

(Bells can change - later ones had webbing and a larger bell cavity - but the bolt locations were the same (the bell being scolloped to take the bolts). So too brace shapes depending on having cable clutches, etc.)
IZU069

Post by IZU069 »

Well I washed her, but she wasn't to horny. Not sure if it's because she expected Christmas presents, or if it was the dirty TG box in the back. But I should get under her tomorrow.

But I did find an engine backing/sandwich plate, though it might be off a Bellett etc.

But it lines up perfectly with the ZZR and Piazza DOHC boxes I recently bought. (There was an extra hole in each box, but there is another hole next to it which the plate also has.)

Here's a pic of the plate:
Image

I also have pics of early and late DOHC gearbox front covers.
The earlier(?) round needle bearing cover has tapped holes for either clutch pivot arm (throwout lever) types.
The later(?) ball bearing large cover has 2 tapped holes only for the cable-pull throwout lever (the second being for LHS cables), but it has a blank for drilling and tapping the pivot bolt for push type levers. (I've seen others fully tapped, or just pre-drilled.)

FYI - interestingly, my TG box has a roundish cover (but) including the ball bearing layshaft cover, but no pivot mounting. The bell housing has the 2 upper pivot mounts (both tapped), but no way of mounting a push type throwout lever. Not that that effects me - all my boxes get the DOHC bell housings.

BTW - "my" gearbox sandwich plate is usually called the carrier plate since it carries all the box guts. So maybe sandwich plate for engine backing plate is the more oft used meaning. My bad.
archangel62
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Post by archangel62 »

Hmm, at first glance that looks completely different to my twincam sandwich plate, however I think it's just the "sculpting" of the irrelevant parts. Mine has a hexagonal cutout in the middle instead of a semi-circle, and I think mine has a few extra bolt holes, but all of the ones on yours seem to be there on mine too. It's hard to say if they'd line up though, due to the perspective of the only photo I have of mine.

I think I managed to get all of the bolts done up around the top, but there's nothing to hold the gearbox along the bottom, and not even those big strong gearbox braces... Which I thought would be there for a reason given their strength and weight. Why don't you run yours? If you don't mind me asking.
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IZU069

Post by IZU069 »

archangel62 wrote:Why don't you run yours? {gearbox braces} If you don't mind me asking.
All these personal questions!

I think it was in part because I find them a pain for access - but it was a long ago I stopped using them....
I also thought that compared to other vehicles, the box itself was more than adequate. (Old Holdens, 4-bolt VWs etc.)

I've never had any problems.
In fact the only gearbox problem I ever had was twisting the output shafts in the G200W Florian (383Nm@3k etc).

As I found when removing a TG gearbox a few days ago, it's a pain removing the damned things.

I'm wondering if I should reconsider their use. But I know no reason as yet, and that's with my habit of flying over rocky & bumpy dirt roads etc (dirt roads are de-restricted aren't they? (lol!)) and having had several rough experiences.

I just mount the lower bolts to the sandwich plate. I reckon the 3 top ones are enough to hold the box up etc. And then there's the side bolts - eg, 2 for the LHS starter; and the shanked locating bolt on the RHS, and another RHS bolt?).
And being 12mm(?) bolts into a solid iron block, I reckon that's enough.

I can supply a better pic if you want.
And I'd be curious to see yours.

Cheers.
Turbocoupe75
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Post by Turbocoupe75 »

IZU069 wrote:

I can supply a better pic if you want.
And I'd be curious to see yours.

Cheers.

Get a room :? :?
#Turbocoupe75
IZU069

Post by IZU069 »

Get knotted. I showed him mine! And in public.
You should have objected then.

Or do you want to know the room number?

(All the above is :lol: - I'm in a cheeky mood - just in case anyone wants to use the above for future reference. lol!)
Greengem20B
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Post by Greengem20B »

The backing plate off my G200W has a different shaped centre "arch" to yours pictured Pete...

As Eli said it has a triangular shaped centre....

I never took note of what shaped backing plate the G180W had on it, though the bellhousing that was on the motor had its bolt holes elongated to fit the G180W. I used my DOHC Piazza box on the G180W and it bolted up fine.

Good luck !
QLD - Home Of The Modified Gemini
IZU069

Post by IZU069 »

It might be a Bellett etc plate then. I might search again tomo... today.
But all bolt holes should still be the same including the 4? bolts to mount to the block.

The lower gearbox cover plate on the Belletts/Florians bolted to the box as well as the top of the sandwich plate.

I think the GW plates have a narrower gap at the bottom, and the cover plate is purely sandwich plate mounted. But I may be way confused? I forget I have a mammary problem.
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