Done some searching and found nothing.
Should I wish to install a later S3 engine, using the original intake manifold and carbs from a Series 1, will I encounter troubles?
Never thought about it before, however read an interesting note somewhere online which made compelling point that due to the larger valves and difference in cam timing, running carbs on a series 3 engine would be funky…
For those who know, is this correct? Anyone done it?
Thank you in advance.
Many have done it…including putting a S3 engine into an E-type. The bigger valve are an advantage either with FI or carbs; there is no difference that I am aware of in cam timing. You may be thinking of still earlier engines with non-parabolic cams, but even then the later cams are fitted without problems and the timing is essentially the same.
Thank you. I just had to hear it.
I imagined as much. I’ve restored and had Jaguars since I was a kid, but it has been a while. I read some post somewhere and it gave me pause, so I had to ask.
While the original head came with the car, the entire motor is from 1983 from what I can gather from the serial number.
Considering finding a donor car of same year (1973) or finding another later model S3 as they can sell for a song, and the block upgrades on the later cars would be advantageous I thought (?)
FINAL question … can I use the entire drivetrain from a S3 car (with the BW66 trans) replacing the BW12 …plug and play?
Thoughts?
I had a S3, and while a reliable and great car, I remember as a kid I did try to drag race a friend (yes what a laugh in a S3) … and revving then popping into D from N the trans died due to some pin which is a known thing with the BW66. Only problem I ever had with that car. Did a John’s Cars upgrade using a TH350 …
While the BW12 is more agricultural it is a die hard reliable box…more reliable than the BW66?
Although a purist, I would consider this as I really never cared about the transmission, it was never a thing for me, a necessary, purely functional necessity, nothing more…using an entire S3 drivetrain as my motor needs a rebuild, and is basically a S3 anyway…
THANK YOU AGAIN for taking time.
**
Jaguar deliberately pursued the policy of evolution rather than revolution, Demian - nearly everything that moves or turns are interchangeable with minimal little…
However, changing from BW12 to BW65/66 is not directly plug and play - while the physical dimensions, bellhouse/box are identical, the controls are different. The former use a vacuum control unit to effect gear changing - the latter uses a cable for this purpose. This entails changes to the throttle pedestal linkages - but basically, each transmission is otherwise selfcontained and interchangeable…
The BW12 is indeed a tough cookie - the 65/66 is indeed smoother, but is less forgiving to misuse…
Frank
xj6 85 Sov Europe (UK/NZ)
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Demian,
I’ve done the engine swap, using the BW12. The only glitch was that the rear of the heads were no longer drilled and tapped where the half-moon seals and throttle linkage brackets bolt up on the early cars. I guess Jag stopped bothering to do this when they knew they would no longer be needed.
It’s easy to drill and tap them while the engine’s out, but impossible once installed. I got the engine all in, just doing the last hook ups before I noticed. For the throttle bracket I made up a bracket off a head stud, which looks odd.
Some gearbox flex plates are different too, swap you old over.
Cheers,
Rob
hello I’m changing my series 1 engine to a series3 with bw12 I have noted the back of the cams are not drilled has anyone have more jnowledge of this set up with pictures please or someone that has done this
thanks
regards
danny
Dear Frank & Rob
Thank you both very much for your replies.
Excuse delay, computer died…using a damn phone now.
I had a s3 but i can’t remember how it was as it was years ago.
Hmm…trying to imagine what you’re saying…
This one does have half moon seals, and there is a thin sheetmetal 90 degree bracket painted black attached to rear cam cover, intake side, for throttle linkage.
As for BW12 trans, excuse me, but where does the vacuum hose attach?
Thank you again.
And i am not one of those who asks questions and disappears.
I hate ppl like that.
I’d been very involved w this forum in the past i might add.
Best
**
I’m probing your present set-up - and how complete your ‘spares’ are, Demian…
The xk engines were essential externally identical through out, readily adapted to various externals like manifolds and carbs generally used over the years by Jaguar - so mix and match is perfectly possible over a wide range. The gearboxes used are all self-contained - varying only in their external connections to the throttle and electrics. The point here is that if the ‘spares’ includes these connections conversions are easier.
The vacuum control used for the for the BW12 is at the rear of the transmission - and is connected to manifold vacuum by a hose. If the vacuum control is missing it must be sourced - the BW12 will not function without vacuum…
The various carbs used differ in linkages used - with the appropriate linkages available, carb conversions are straight forward. Makeshift adaptions are possible of course…so…?
Frank
xj6 85 Sov Europe (UK/NZ)
**
Demian, the vacuum hose connects from the inlet manifold to the modulator - which is located at the rear lower right hand side of the BW12 - looking from the rear of the transmission forward. The modulator converts the vacuum signal into shift instructions inside the box. Paul
Got it. Thank you both.
Gosh, i haven’t yet gotten beneath this car seriously…sigh.
It’s clean though, no major leaks zero rust ever…so…we shall see.
Very helpful…have the old maroon xj6 manual but i can’t recall seeing this info
Bit late to the party, but I did it sucessfully to my previous S1, and will do so again to my current one once the motor gives out. As I recall there were only 2 holes to drill and thread on the kickdown plate linkage. Also note the connections to the oil cooler.
Regards
Cds
Thank you!
Never too late…I’m slow anyway.
My additional curiosity or thought is if I have the option, should I replace with an original year motor and rebuild it, or rebuild one with the later upgraded 4.2 block as on the S3?
hmm…I have possibility of buying a '72 S1 complete car needing much help, ,but original.
Great info in that thread by Bob Wilkinson btw…
As I haven’t had a S3 in years, the drilled and tapping at end of cam referring to is the half moon seal cut-out?
On another tangent, mine has the half moon seals. Is it then the original head on a later block?
On yet another note, my tach doesn’t work … I recall the S3 had a transducer or something on the end for the tach…and the S1?
Final curiosity, my head has a raised, stamped number “10” within a square at the center btw plug holes 4 & 3 …meaning? I thought perhaps 10:1 compression…but naahh…I’m getting 130psi on all 6 cylinders.
Any thoughts and opinions genuinely appreciated.
Hi Demian,
Are you in a LHD jurisdiction?
I’ve got an S1 car with a late S3 engine, and a reasonably original S1 hulk which is mined for parts (RHD cars).
This cut-out is machined, but not tapped, is similar if not the same as the lower half of the cam bearing bore. The arrangement at the back end of the cams evolved from S1 to S3. Early cars have the other half of the moon cut out of the cam cover, later cars do not. As far as I know they all have the lower cut-out.
So not neccesarily. I have an S1 head that has hex-headed screw-in plugs between spark plugs. The S3 head has freeze plug style closures there. I the manifold is off, inlet runner diameter will also be an indicator. With the head off, intake valve size also.
S1 tach works off the ignition wire from the key on it’s way to the coil or ballast resistor. There should be info elsewhere in the forum to help troubleshoot your tach issues. Is your ignition set-up std S1?
My S1 head has this, although it is cast rather than stamped. My S3 has “11” cast in a more rearward position. Both heads have stampings on a cast pad right at the rear end of valley. No, compression is indicated by a subcript on the engine number. Your readings are 20-30 PSI lower than my 9:1 with substandard valve clearances and glazed bores, so maybe yours is an 8:1?
Cheers,
Simon
Kalgoorlie
Thank you Simon.
Appreciated and helpful.
Who the hell could one talk to on this stuff without the internet?
Yes, LHD…all original except s3 block and perhaps head.
I thought about that later, i meant cast, that “10”…
Also know exactly what you mean regarding freeze plugs there and stamped little plates/pads at end…
I was given another complete head with the car, i imagined that was the original and this is a complete s3 engine installed.
Hmm…hope it is a compression difference, sigh…
Must be 8:1, US s3 xj6, yep…
This must be later head as the rear of cam cover is flat.
Those are the images from the back of the head of my S1. You can use the plate itself to mark the position with transfer punches, use a caliper and
It’s depth function to calculate how deep you need to go.
As far as I recall s3’s have different water passages due to the block modifications to stop the cracking issues, so I do t think it’s possible to have an s3
Block with an S1 head unles los the head is modified,
Thank you for thoughts and images.
Good to see, i understand what people are talking about now.
Right, mine is a S3 head on S3 block…the extra i have must be original S1.
