XJ6 & XJ12 Series I, II & III 1968-1992

Swapping BW12 for a BW66

 
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Old 05-26-2016, 02:24 AM
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Default Swapping BW12 for a BW66

Just a quick question that will probably turn into a 100 post thread.
Dr Phill and I picked up two series 3 BW66's from another forum member today for cost of the fuel to drive there. One came from a running car.

I have no issues with my BW12 right now but it is the only part of my running gear that hasn't been restored/replaced.

Is it a straight forward swap, and what is involved?




 

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Old 05-26-2016, 03:56 AM
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Ya pushing the memory cells now mate.

Bolt up, yes.
You will need a S3, or at a push a S2, flywheel (driveplate to some).

The BW12 is vac modulated, the BW65/66 is cable modulated, soooooo, you will need a S2 throttle linkage rear section with the "double bellcrank" to work the carbs and the trans cable.

Mount at the rear will be OK.

Prop shaft same length from memory??.

Your starter should also be OK, as in mesh etc with the updated flywheel.

I did it on my S Type 3.4ltr, which had the BW DG, the predecessor to the BW12. It was rod modulated, so HEAPS of mucking around to get the cable adapted, coz the S2 stuff I mentioned above would NOT work on the S system.

That BW12 is TOUGH, and is for most part an FMX in disguise. Some innards are hardish to find, but as a cast iron unit, good as they come. They used it behind the early V12's.

Mate of mine went the opposite way with his S2 6 cylinder car, a very long time ago. That was fun.
 
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Old 05-26-2016, 04:41 AM
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Originally Posted by Grant Francis View Post
Ya pushing the memory cells now mate.

Bolt up, yes.
You will need a S3, or at a push a S2, flywheel (driveplate to some).

The BW12 is vac modulated, the BW65/66 is cable modulated, soooooo, you will need a S2 throttle linkage rear section with the "double bellcrank" to work the carbs and the trans cable.

Mount at the rear will be OK.

Prop shaft same length from memory??.

Your starter should also be OK, as in mesh etc with the updated flywheel.

I did it on my S Type 3.4ltr, which had the BW DG, the predecessor to the BW12. It was rod modulated, so HEAPS of mucking around to get the cable adapted, coz the S2 stuff I mentioned above would NOT work on the S system.

That BW12 is TOUGH, and is for most part an FMX in disguise. Some innards are hardish to find, but as a cast iron unit, good as they come. They used it behind the early V12's.

Mate of mine went the opposite way with his S2 6 cylinder car, a very long time ago. That was fun.
Both have flywheels, so good there.

Came with a prop shaft too.

Yep, the BW12 is tough and working well. Track days proved that. The parts I have replaced on it were from an FMX part number(I had one of those in my Falcon 351 coupe and never broke it)

Swapping BW12 for a BW66-hardtop-1.jpg

Not planning a transplant right now, just dipping a toe in the water to see what is what. It was an offer I couldn't let go considering the age and availability of spares.
Having done nothing to the trans except a couple of parts, they are worth putting in my stockpile and doing some research.

I'm sure Dr Phill will do some poking around too.
 

Last edited by o1xjr; 05-26-2016 at 04:51 AM.
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Old 05-26-2016, 07:44 AM
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IMHO the BW66 is a good gearbox (as elderly designs go) but it is on the verge over being over-taxed as used in the Jag sedans. I think you'd be downgrading slightly.

The BW12 is beefier.


Cheers
DD
 
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Old 05-26-2016, 04:42 PM
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My series 1 had a BW66. I believe that is why the speedometer readings were miles off.
 
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Old 05-26-2016, 09:23 PM
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I would just like to add Clarke, I think the "Fireball' is quite ok how she is. if its not broke don't tamper with it. Leaves more time for drinks.
 
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Old 05-26-2016, 11:31 PM
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Originally Posted by Dr Phill View Post
I would just like to add Clarke, I think the "Fireball' is quite ok how she is. if its not broke don't tamper with it. Leaves more time for drinks.
Originally Posted by o1xjr View Post

Not planning a transplant right now, just dipping a toe in the water to see what is what. It was an offer I couldn't let go considering the age and availability of spares.
Having done nothing to the trans except a couple of parts, they are worth putting in my stockpile and doing some research.
Don't panic Phill, you still have a free weekend. By the sound of it so far the BW12 is the better tranny to stick with. But if it goes pear shaped I do something up my sleeve.
 
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Old 05-27-2016, 09:37 AM
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XjeeJ:


Don't think so. Top gear is straight through on either.


But, as a cable driven speedo, the little plastic gear
in the box that drives the cable may differ from one box to
another. there seems to be some tolerance in tooth matching???


My lump's speedo is off a lot. I know how to fix it and have the
device to do it. But, I merely drive by tach or interpret as I knw the error. No tinkering, it works.


Errands today, in the Jaguar...


Carl


Carl
 
 
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