what/which 115amp 120amp alternator can I fit as a direct replacement for the Lucas unit on an 84 xjs?

 

That I know of, you can't.

If you get the Bosch 115 your big problem will be finding a v-pulley to fit it. My experience has been that the bigger Bosch unit, if you buy one at an auto parts store, doesn't come with a pulley, and the pulley off the Lucas 75 amp won't fit the shaft on the Bosch. I tried to do this and while it wasn't a big deal to figure out how to hang the bigger unit off the existing bracket the pulley issue killed the project.

There are other alternatives (see Palm), but as far as a direct (easy) swap, I don't think there is a bigger alternator that will fit.

Thanks,

John
1987 XJ-S V12
63,000 miles

 

RGP, My car ate alternators until I took Grant's advice and put on a 115 amp one. The 115 version from later cars will fit OK. I bought mine from a very good specialist place in Plymouth the UK, if you want a link message me.

They supplied a normal V belt pulley with it and some washers in various thicknesses so i could align the pulley with the crank pulley easily. I have had no slippage and it has absolutely transformed the electrics.

The only fitting wrinkle (from memory) is that the holes in the 115 alternator casing fixing lugs are a larger diameter than the original long top bolt the 75 amp alternator is hinged on. This required the alloy bracket on the block to be removed too and some drilling of it to accept a thicker long bolt. Something of that sort anyway. It is obvious when you get there.

While you are at it, if you have not done so already, the Grant Francis heavy gauge cable to the starter from the alternator, plus a supplementary earth strap from the alternator bracket to the frame can usefully be done too. Always a job on an XJS...

Greg

 

As Greg said.

Since you in the UK, I reckon simple as.

The units supplied down here are Bosch, and come from the XJ40 era Jaguars. YES, the pulley is different, but Bosch kept the shaft the same diam for ever, so a Bosch "V" fits.

The long bolt on the upgrade is 10mm diam, the old unit is 8mm, so yes again, drilling the alloy bracket is required.

Wiring upgrade is mandatory, as also said.

The rest is as is, even the belt is the same size.

 

hi Gregg, was it this
The Starter Motor & Alternator Company Ltd
I have e mailed them.

 

Yes, they are the guys. I asked for a 115 as use on all later 1990s Jags. Be sure to ask for one with the correct "clock face" (ie Swivel lugs at 10 minutes past and adjuster lug at 20 past as you look at the front).

As I mentioned, they will send a V pulley for you to fit onto the spindle of the alt and a few washers so you can align it first and then fit the pulley. Really decent guys with me.

Greg

 

hi Gregg. can you do me a favour, they want pics and the readings of the plate?
this is the mail I got, but I don't want to disable my car to fid the info


"However, if you look at the red arrow on the pic attached, there should be a
small plate somewhere near it, could you tell me exactly what it says on
that plate? (part numbers and exact amperage) as we may have something
slightly more powerful than the existing one"
thanks if you can help

 

Sorry RPG about steering you wrong! I just wish I could have made that work.

We have a grand total of one "alternator shop" in town and the guy was just not willing to really do anything for me. So without a v belt pulley I didn't see any way to continue.

Maybe I need to look harder. I'd really like the bigger alternator...with as little work as possible :-)

Good luck with it!

John
1987 XJ-S V12
63,000 miles

 

The later V12's my 1989 5.3 for instance runs the alternator on a 6 rib serpentine, all other belts are V. Find a later harmonic balancer with serpentine. Just another option.

 

RGP
I am not sure what they want and what 'plate' means. Can you send me a copy of the pic? I found it better to call them, by the way. I just said "send me a 115 as used on the later 1990s jags" (with the clockface as required).

I have sent you a PM on the forum system with soem info that should allow the company to find what they supplied to me.
Greg

 

I have sent them the info you have kindly sent and I hope they help i.d. it
the label the are after is missing on mine unfortunately