today I ordered the Powerhouse supercharger crankshaft drive pulley, which is 10% oversize and comes with a longer belt, and drives the Eaton blower at 10% more revs so more mid-range power/torque, but heat-sink at full throttle kills off top-end power gains.
But who drives an XJR at 5000rpm? not me

I still want headers/extractors, but nothing sorted yet, and plenty of threads on that topic already.

I have considered changing the diff from 3.27 to 3.54 (std 4 litre X300) but none available in NZ at the moment

I'll post on the pulley once fitted in a few weeks..

 

I think the differential would be a more cost-effective upgrade than the pulley with no side effects on the supercharger cooler, and wonder if the pulley AND differential combo be an overkill?

 

See item # 22 Crownwheel and Pinion

https://www.jaguarclassicparts.com/u...ponents-normal

And for Power - Lock ( limited slip )

https://www.jaguarclassicparts.com/u...nents-powr-lok

If I understand correctly you don't have to ship a whole differential but just the 2 components from the donor car from outside New Zealand to save on shipping cost . You'll want to change the 3 + bearings including the 2 output shaft bearings while you have yours apart . That way you know you have a % 100 zero time overhauled differential .

 

Would you mind scanning or posting all of the instructions & specs such as bolt torque and belt part numbers from the kit?

That way anyone trying to find that info later might be able to search for it.

Let us know how the install goes. I have yet to install mine until I can add some additional intercooler capacity by using the OEM oil cooler as a piggyback and/or seeing if an X308 intercooler radiator will bolt on and is actually larger capacity.

.

 

I believe the XJ40 differential internals are the same, so if you can get one of those you can swap it across.

 

Probably depends on the type of driving you do. The combination of the pulley and 3.27 gives more torque for acceleration, but gives better fuel economy on highway cruise. Obviously the 3.54 would give stronger acceleration, at the cost of fuel economy.

I changed my NA VDP from 3.58 to 3.77 to get a powrlok for use in the winter. The ratio change cost me about 2 mpg in cruise fuel economy. At the time, Andy's bracket and the pulley were not available. I'd go those routes before a diff change now.

 

I bought a 3.54 differential from the UK before recovering Rose (my converted manual XJR), and it is still sitting because since Rose was reborn, her current level of performance is already adequate (Andy has remapped my ECU to incorporate the timing advance). At 2500 rpm, 5th manual gear and with the stock 3.27 differential, Rose can do 120 km/h. However, I know with the 3.54 differential I would gain faster acceleration at low gear, but I like accelerating at mid-range instead. Indeed this is a matter of personal reference. X300 is a very heavy car, so I would rather let her roll off with some grace and then surprise others from behind.

 

I swapped the 3.27 rear end on my XJR for a 4.01 from a 3.2 because the original rear end needed new bushes / bearings and I had the complete 3.2 assembly in my garage, so free and easier than rebuilding the original. I also thought the performance gain would be a fun. It is quick of the line now, and spins the tyres as it shifts into second, which is fun but you have to be careful with it. However overall I prefer the original gearing as once rolling in normal use it feels more relaxed and overall the low gear detracts more than it gains. A 3.54 might be a better compromise.

 

With a manual I suspect that the original 3.27 gears would be best full stop as one can always slip the clutch to allow more revs for a fast start, if desired. A lower gear would spoil the car in my opinion.

 

Sorry, 3.54 should read 3.58 which comes from the 4.0 NA version. In the case of an XJR and a manual gearbox, perhaps the 3.27 would be a better match, as the driver has better control when to up shift. The 3.58 would give the auto gearbox more punch at all gears.

 

The only reason for the 3.27 was for the magazines to give a nice 0-60 time with a manual transmission. If it had a 3.58 then there would have to be a 2-3 shift as you'd hit redline before making 60 mph in second. The time it takes for the shift would make it slower than an automatic, so that's why the XJR has the higher ratio.

With the NA cars the 0-60 times are not as important and over 95% of them were automatic anyway, so the 3.58 gives a bit more performance.

Early XJ40's were 3.54, then changed to 3.58. The 3.54 ring and pinion is the same as the XJS, the 3.58 isn't; the pinion is different and in one piece to have the locating pin that goes in the driveshaft. The 3.54 has a separate adapter piece to provide the pin.

 

Got the car back today with new 110% supercharger drive pulley fitted, also needed an intermittently faulty coil replaced (luckily I bought 4x “Made in Japan” spares 2 years ago). It is going beautifully, definitely more power, though still less than the 2011 XJL Supersport I tried a week ago...! (510bhp)

I would recommend the pulley (and the Supersport)

Only word of caution...the AC belt tensioner was just rubbing on the new larger pulley so my mechanic had to get a shorter belt for the AC pump. In fairness to Powerhouse, the AC belt may have been stretched or the incorrect one to start with...

My next step is to consider headers/extractors.. I am thinking about finding someone who could make a batch of 10 and see how they go if anyone is interested. Not easy to find someone in my town to do them, let alone in Stainless steel. I’d be happy with mild steel - they’ll never rust out. However I seem to be in a minority.

In the photos, pulley is the shiny new one..

 

Excellent, very interested to hear your "seat of the pants" review of how the car feels with the new larger pulley installed. Also interested to hear if you can maintain the increased boost, or if you get heat soaked quickly.

Odd about the A/C belt tensioner rubbing, as I've not heard of that happening before. Hopefully the old belt was stretched or was the incorrect length. I guess one could use a slightly smaller tensioner pulley too.

Still curious if anyone knows the correct torque spec for the four bolts that hold the lower pulley on.

 

Al, get your pulley fitted! It makes a difference that is worthwhile.
I haven’t noticed significant heat sink yet, but will let you know if it happens. I did replace my tired original Hella pump with the modern Bosch pump last year which made a huge difference - almost no noticable heatsink except on very hot days, whereas with the old Hella it was quite noticable

 

Really the best ratio would be the 3.58 from the 4.0 and 3.6 N/A XJ40/ X300. Be careful which crown wheel and pinion you get as some have the UNF nut that is NLA. So you need to use the used nut. The crown wheel and pinion can be changed over but you will need to make sure the person doing it is competent.

The only other issue that you may have to be aware of is and it may not be a problem but the ABS and if it has traction control. If you change the ratio the car may think the wheels are spinning. We have had this on other models, mainly the later ones. Diff ratios are quite crucial when the car gets ABS.

Worth looking into.

If you need crown wheel and pinions we have them in stock.

Regards,

Ben

 

Thanks Ben,
I meant 3.58, I always get the ratios tangled up.
What can be done about the ABS sensor if the diff is changed?

I just googled your company - sounds good, liked the articles about the 5 speed.
I see you sell both Getrag 265 and 290. From memory the 290 is on the XJR - is that a stronger box than the 265 ?

I am a Kiwi, but it’s a small world. I lived in Abinger Common for a year, seven years ago, and went to Dorking often. I even have the “Dorking white squirrel” T-shirt to prove it!

 

Diff ratio changes will not affect an X300. It's later cars like the XK's that run into problems with transmission shift point programming etc.

 

OK it looks like the ratio will not affect the traction system which is good. I wasn't sure if it did affect the X300.

Yes we sell both 265 and 290. Stock does vary but we have both in stock.

Yes very small world! Abinger is a great place. If you need bits in NZ I can help.

Good luck!

Ben

 

Also yes the 290 is supposedly stronger. To be honest the 265 does the job great. We put them in applications up to 7.0 litre V12's. As Listers would have said, a 265 is good up to 600hp. We haven't tested that but I could believe it.

We have over 200 V12 manual conversions sold with that box with only a small handful of issues, quite amazing really!

 

Ben, tell your dad this story. It has nothing to do with Jags, but is a true Abinger story..

5 years ago, recently returned from UK, I met an older gentleman, and he mentioned when he flew for BA in the 70s, he lived in Dorking.
I said, that’s my old supermarket shopping town, I lived in a small village 6 miles away.
He - “What’s the name of the village?”
I - “You won’t have heard of it - Abinger Common”
He - “I used to drink in the Abinger Hatch”
Me - “I used to drink in the Abinger Hatch”
He - “Ahh, yes, but I used to drink in the Hatch with Oliver Reed”
Me ...trumped