Let’s think about this one logically.
Assuming you’re talking S30 Z with L-series engine:
Things you don’t need
1. The clock does nothing
2. Speedo not needed to run engine.
3. Water temp / oil pressure gauge not vital to running (except knowing you’re up to temp or that you have oil pressure). As long as you’re confident the engine hasn’t got oil pressure isssues and the cooling system works, then you don’t NEED them to run the engine. You can always use an infrared or other thermometer to track water temps at the radiator. I’d like to know this myself so as to avoid accidental over-heating.
What you do need
A. You will need the rev counter connected for the ignition to work as the low tension wiring from the coil goes through the back of the rev counter’s inductive pick-up. You can bypass this using a couple of spade connectors and a piece of wire to make a jumper for the connector block.
I believe it’s the coil positive that goes to the tach, so alternatively you can just add a direct connection from coil positive to the battery positive, but FUSED (5A) as close to the battery terminal as possible; a) to avoid a car-b-q and b) to be able to stop the engine by pulling the fuse!
Note: running a direct feed is also bypassing the ballast resistor (if one is installed), so make sure your coil is designed to run without the resistor (e.g. something like a flamethrower 1.5ohm coil). You can run the a ballast resistor type coil this way (I have done it while experimenting for 30 mins), but it will heat up quite a bit and may damage the coil. Also not great if you’re running points ignition as it will damage the points. Or if you understand the wiring, just connect it to the correct side of the ballast resistor (you can just buzz this out with a multimeter to determine which side is connected to the coil and connect your direct feed to the opposite side of the resistor).
B. If running an Ammeter / Fuel gauge, you need that one connected otherwise your alternator won’t work. If Voltmeter / Fuel gauge then you can get away without connecting it as the Voltmeter is only sensing and not vital to the operation of the alternator.
You can just disconnect the alternator and run the engine on the battery for a good while; also with a high output battery charger connected to the battery if required. Mine has a slow charge (upto 5A), fast charge (upto 15A), high output / engine start setting capable of delivering upto 80A.
Without everything else connected and just engine running, your ignition system needs c.3A max. A fully charged 90Ah battery should be good for the 5-10 mins you need to get the water temp up. Unless of course you need more juice for an electric fan (if installed).
Hope this rambling from an insomniac helps a little!
Keep us posted how you get on.
sounds easier! Have done the basic leak tests but got nothing I can see while not hot and under pressure.
Appreciate the offer, will let you know.
