I am doing an engine swap, as part of this the alternator will be
going in with the engine. The issue is that it is a 70 amp alternator,
and the car is more used
to 34/43 amps.
Do I need to worry about anything other than increasing the size of the
wire from the alternator to the battery to handle the extra current ?
or should I be making changes to the loom as well?
Thanks for any advice.
The alternator size does not matter, it's job is to provide current for the
battery, which in turn runs all the electrics in the car. If you car only
needed 30amps before, then it will only need 30 amps now, if you were to
have say a kettle running in the car and a few subs and amps etc then yes
you may need to up the wiring.
Current is drawn from the alternator it doesn't actually give anything
unless it's needed.
Thank Ronny, it's actually a V8 with an electronic ignition going into
an MGB. It's carbs, not EFI. So thats something. I'm assuming that with
a beefier starter it will draw more current.
What bits of wiring should I be looking at ? just ignition/engine
Hmm, kettle eh?
Didn't realise you were doing a V8 lol, that would need some oompfh to get
it started, so def use the above cables from the old car, but the rest of
the wiring will be fine :)
Also you will need to upgrade the battery to provide the extra amps when
cold, so try and get the one from the doner car.
Car loom will be fine unless you are adding extra equipment like higher
wattage headlamp bulbs / extra lights etc etc, but that is irrelevant to the
With regard to the alternator, increase the gauge of the wire from alt to
battery, AND check the engine earth strap from block to body and or to
battery neg is also of sufficient capacity for at least the max output of
Leave the loom alone, the headlights and whatnot will draw the same current as
TBH, the "correct" solution is to use the wiring for the bigger engine, in
terms of starter motor and wiring to the battery from the alternator, and the
coil. This is correct for the engine. Similarly you should use the battery from
the donor or one listed as suitable for that engine.
But on the other hand, if you don't have these bits available, use the old
battery, old wiring. It'll work, most likely, and if it melts and starts a
small fire you'll fix it the same way as you'd prevent it, i.e. buy a larger
battery, fatter starter cable, etc. Might as well let it fail and avoid that
cost if it doesn't.
I still have the loom from the old car, and all the ignition bits and
was planning to re-use them. It was just that I wasn't sure what
effectit would have on the rest of the loom. But you have all cleared
it up for me, thanks for your advice.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.