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Avoid over-gunning your classic Ford’s precious engine with this easy-to-fit device that sets an adjustable rev limit. Here’s how to fit a rev limiter.

The beating heart of any classic Ford is, of course, its engine, and if you’ve spent a fair few quid either buying one, or having one built, then you’re going to want to do your best not to damage it — especially by over-revving it when getting a move on. One of the ways to prevent this happening is to fit a rev limiter. 

Modern cars have rev limiters built into their ECUs, and classic Fords running aftermarket ECUs have this luxury too, but if you’re still running a distributor-based ignition system then you can still set a rev limit by fitting a standalone unit. These take their readings from the coil (much more accurate than a rev counter), and once the engine revs reach the set limit, will interrupt the signal to the coil, slowing the firing sequence, and preventing the engine from increasing its rpm.

There are various rev limiters on the market from the likes of Armtech, Lumenition, Micro Dynamics, MSD and Omex — we went for the latter’s Clubman unit, partly because it was the most compact (so we could tuck it away out of sight under the dash), and partly because (when sourced from Rally Design) it worked out the cheapest. Fitting is straightforward — just three wires, two of which can connect directly to the coil, and setting it up is a simple case of pressing buttons.

The Clubman unit can be configured to work for two, four, six and eight-cylinder engines (the default setting is four), and you can also specify a hard or soft cut of the revs — on soft cut (the default setting), the limiter will gradually limit engine power 200 rpm before the set limit, which is less harsh than the hard cut. 

The Clubman unit’s maximum rev limit setting on a four-cylinder engine is a dizzying 20,000 rpm, though if you can make a classic Ford engine rev that high, give us a call! The limit’s set at the factory to 6000 rpm, but we decided on 5800 rpm for the 1700 Crossflow it’s being used for – the engine makes peak power at 5600 rpm, so there’s little point revving it much higher.

Read on to find out how to fit it, and set it up.

how to fit a rev limiter

Here’s the install kit. As well as the limiter you get T-crimp connections for joining to existing wiring (we connected the limiter’s wires directly to the coil instead), a terminal, screw and spring washer for the earth connection, and cable ties to route the wiring. 

how to fit a rev limiter

Disconnect the battery. Decide where you want to mount the limiter — it can be mounted in the engine bay, as long as it’s not too exposed and is positioned away from heat, the distributor or coil. We’re mounting ours in the car, under the parcel shelf using the adhesive pads supplied.

how to fit a rev limiter

If you’re mounting the limiter inside the car, you need to run the wires from the limiter through the bulkhead into the engine bay. We’ve used an existing hole to do this — we’ll add a suitable grommet later.

how to fit a rev limiter

Run the red wire to the positive (+) side of the coil. You can use a Lucar connector like here, or just use the cable connectors supplied to crimp the wire to the existing feed to the + terminal or positive feed activated by the ignition switch.

how to fit a rev limiter

Now run the violet wire to the negative (-) side of the coil.

The black wire needs to run to an earth point on the bodywork with the eyelet, self-tapping screw and spring washer supplied. Tidy up any loose wires with the cable ties, reconnect the battery, and you’re ready to set up the limiter.

Setting the number of cylinders

Press and hold the + button on the limiter and turn the ignition switch to on (but don’t start the engine). The two LEDs will show the cylinder setting — both unlit means it’s set to the default of four-cylinders. To change this press the + button until only the LED 1 is lit (six-cylinders) or LED 2 is lit (eight cylinders).

Setting the hard/soft cut 

Turn the ignition off. Press and hold the – button and turn the ignition on again — LED 2 will light meaning soft cut is active.

To change it to hard, press the + button and LED 1 will light. To change it back later, repeat step 8.

Setting the rev limit

Turn the ignition on, then press both buttons — both LEDs will flash.

To lower the rev limit from the default 6000 rpm setting, press the – button — each time you press it, you will lower the limit by 100 rpm, so to change the rev limit to 5800 rpm, press the – button twice. To raise the limit, press the + button to increase it 100 rpm each time.

 

If you make a mistake and need to reset the limit, turn the ignition off, press and hold both buttons, then turn the ignition on, both LEDs will flash, and the limit will be reset to the factory 6000 rpm limit. Change it to the setting you want, and that’s it, you’re done.

Words and Photos Simon Woolley

This how to fit a rev limiter guide first appeared in the February 2019 issue

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