Hello Jagies,
I went to some of the alternator threads but was not able to find an answer. I have the original BUTEC alternator mounted in front of the engine but was thinking of an alternative to go with the XJS mountings on the RHS as I have dropped the air-pump stuff.
Can you recommend an alternator that I might be able to use and what idler could be used ?
p.s: I have a Series 3 73 2+2
Thank you
Tom
If you’re sticking with reverse mount, you can use a Bosch of 60-90a, with the addition of an Omni or cow fan, to give you about the same capacity as the Butec. If you need more output, the later Bosch units out of something like a 210 Mercedes will put you over 100a, and they have Omni directional fans.
If you switch to a forward mount, almost anything can work. Probably a Delco would be the simple choice.
Above 100a, you should be using a SERP belt and overrun pulley.
Another option here
I am using an alternator from an xjs in the smog pump position.
kind regards
Marek
The early XJ-S alt was a Lucas 70-amp. Those XJ-S owners who experience trouble often opt for a Marelli alt from a newer Land Rover of some sort, more amps, more reliable, fits exactly the same mount scheme.
The later XJ-S, after about 1988 or so, went to a Bosch alt of 115 amp. The mounting is different – utilizes a larger pivot bolt, I believe – and it’s driven by a ribbed belt rather than a V belt. The introduction of this alt corresponded with the onset of crank damper problems; the damper would fail and the outer ring would start slipping, causing a failure to charge the battery (the alt is driven off that outer ring of the damper) and people would go nuts trying to figure out what’s wrong with the alternator. You’d generally have to mark the ID and OD of the damper and then run it a while and check to see if the marks are still aligned to confirm the damper failure.
Other XJ-S owners opt to toss the OEM alt and install a GM alt in place of the air pump. The air pump mount is remarkably similar to a GM alt mount (completely different than the Lucas or Bosch alt mount), only requiring some spacers on the pivot bolt. Ideally, the GM alt needs to have a pulley designed for a 5/8" V belt (typical is 1/2" V-belt or ribbed belt) but that is findable; it’ll be a bit larger than the typical alt pulley, so it’ll turn slower – but modern GM alts charge very well at slow speeds. The CS130 is an excellent choice, and the CS130D (completely different than the CS130, hence the D for “Different”) will also work.
Finally, John’s Cars offers a kit for installing a GM alt in place of the Lucas alt. It’s an entirely new bracket. Quite popular.
Thank you for your answers. Is the alternator supposed to be driven by the smaller wheel used for the smog pump and a double idler pulley instead of the original alternator or will it reach as far in front and have two wheels as well ? @MarekH: Do you use the crank pulley from the XJS ?
Found this pic with a double pulley idler:
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I mix and matched pulleys. The first belt is to the alternator and there is a single second belt (via the water pump) to the power steering pump.
There may be some pictures posted in the old photo albums or in one of my other posts.
kind regards
Marek