Alternator questions

[mangocrazy]

I have a couple of questions relating to alternators that I'd like answers to. The first question relates to mounting it to the engine. I'm happy with the top and intermediate mounts and have all the parts needed for that, and am aware that on my S2FL Spider the bottom mount is taken off the front of the oil filter block. What I can't seem to make out is what size the mounting bolt is, and what spacers (if any) are needed. There is a threaded insert that screws into the front of the oil filter block, and has an M8 hole drilled through it, but my alternator (a NOS Valeo item from Chris Bastow many years ago) has M12 inserts fitted that don't appear to line up with the mounting point on the oil filter block, as well as being a much larger fitting.

So my first question is: What size bolt do others use for the lower alternator mount? Does anyone have a photo of their lower alternator mount? (OK, that's 2 questions...)

My other query relates to the alternator output. I believe that the OE alternator was rated at a paltry 55A. The NOS replacement I have is rated at 70A, which is a definite improvement, and I'm also aware that there are 95A WOSP units available (at a price). What would you consider to be optimal in terms of alternator output? Would my 70A unit be sufficient, or should the 95A WOSP unit be on my shopping list? (and yes, that is also 2 questions...)

Thanks in advance for any replies.

[WestonE]

Hi Graham some answers for you.
The Beta IE used 65amp and for most peoples needs that is enough even with Fuel Injection and electric windows. It should be paired with a suitably larger battery. Of course if you are planning a major sound system with multiple high power amplifiers or big spot lights you will need a high power alternator.
On the subject of spacers what matters is belt alignment and a stable fitment. Off to one side or the other or moving about in service are both a very bad idea. You can get different alternator bolt inserts and longer bolts simply enough. I use 10mm bolts in my installations and have a dislike of aging  Beta rubber mounts with an 8mm hole. I do not like the load on the belt and the bearings from the alternator moving about in use.

 
Enjoy

Eric

[mangocrazy]

Thanks Eric. In that case I'll save myself around £450 and use the 70A alternator I have. I don't have electric windows (for which I'm thankful) and don't intend to have earth-shaking bass in the place, so 70A should be more than sufficient.

So now I need to figure out bolt and spacer sizes. Not too much of an ordeal, hopefully. Like you, I want a rigid and reliable mounting for the alternator.

Graham

[peteracs]

£450? Crikey you have just got to need one for that money…..

Peter

[WestonE]

BTW for the Electric AC on the Monte I have to have an alternator with at least 140amps!   

[mangocrazy]

£450? Crikey you have just got to need one for that money…..

Peter

That's the cheapest I could find. £492 from Betaboyz...

https://353652584127257704.weebly.com/store/p916/95Amp_Denso_Race_Alternator__V_-.html

An extra 25A output (that I don't really need) and a couple of kgs of weight saved are not reason enough...

[peteracs]

Hi Graham

A quick search shows 90a alternators for around £100-£200. I know we need specific mounting points and pulley sizes etc, but there has to be one suitable in that range?

Peter

[mangocrazy]

Hi Peter,

That's a far more reasonable price range. As long as the pulley size/shape is compatible, most other things can be fixed. The WOSP one does shave a kilo or two off the weight being made from aluminium, but that's largely immaterial given the exorbitant price.  Anyway, I have a 70A one made for the Beta so that will be getting fitted.

Graham