Jaguar Specialties
Innovative and Unique Products for Jaguar Cars

Telephone: 408-839-5569

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Last Update 1-3-18

Other Wiring Components

 In addition to the basic engine harnesses offered for some models, there are several other key parts Jaguar Specialties offers to help in the wiring of your conversion:

  • Tachometer Interface Unit- To get the Jaguar tachometer reading correctly with the new V8 engine, something has to change in either the tach itself, or the signal going to it. The easiest way to correct your tach is to use the Jaguar Specialties Tachometer Interface Unit. This small  module goes between the V8 distributor and the Jag tach, or between the GM engine computer and the Jag tach (for LT1 and LS1-LSx engines). The module is programmable for the proper signal correction (8 cyl eng to 6 cyl tach, 8 cyl eng to 12 cyl tach, etc.,.) and is very simple to hookup with just 4 wires: + 12 V Ignition, Ground, Tach Signal In, and Tach Signal Out. What's nice here is that it leaves the Jag tachometer stock, so if you ever had a problem and need to replace the tachometer, another stock Jag unit can be installed and will read correctly without any further work. The module is less than half the size of the a pack of cigarettes, so it can easily be hidden anywhere under the dash, or even in the engine compartment.

  • VATS Bypass Unit- starting in 1986 (with the Corvette) and then from 1989 on with Camaros and other cars/trucks, GM added the "VATS"  (Vehicle Anti Theft System) to its cars. This system was pretty simple, and provided a special signal that gave the engine computer the ok to allow the engine to run. Originally, the system used a special resistor (one of 29 different values) buried in the ignition key; a separate module in the car read the resistor, and if it was correct, sent the required signal to the engine computer. In engine conversions, we rarely get the VATS module with the new engine/wiring/computer, and without that signal, the engine won't run. Jaguar Specialties now offers a simple "VATS Bypass" unit that is easy to install, and provides that signal to the computer so the engine will run. Using this very inexpensive module makes it unnecessary to use custom chips (for TBI or TPI) or  have the computer reprogrammed (LT1 and LS1). The module has just 3 wires: +12V Ignition, Ground, and VATS Signal Out (to the computer itself). What's nice here is it allows the VATS system to remain on the car, so it can be used a security feature when desired- a hidden kill switch can be installed in the power lead to the module, or a remote alarm system can be used to kill power to the module when armed. Either way, the engine won't run until power to the module is restored. And that anti-theft  is provided to you by GM with your standard programming- free of charge. As you can see, using the Jaguar Specialties VATS Bypass Unit makes a lot of sense

  • LT1/LS1 Speedometer Interface Unit- Starting the the LT1 engines in 1993 and to current day, the speedometer speed signal to instrument cluster feeds directly from the PCM (engine computer). For the 83-87 XJ6 and XJS models that used an electronic speedometer, this poses a problem as there is no mechanical way to drive the original Jaguar speedometer transducer that was originally mounted on the transmission. The standard GM speedometer output signal will not drive the Jaguar speedometer properly. To solve this problem, Jaguar Specialties offers a special LT1/LS1 Speedometer Interface Unit that converts the standard GM speedometer signal into a format the Jaguar speedometer can use. This is not a generic module adapted to this application- it was designed specifically and only for Chevy/Jaguar conversions like this, and is available only from Jaguar Specialties. The wiring is very simple and is just 4 wires: +12V Ignition, Ground, Speedometer Signal In (from the GM PCM), and Speedometer Signal Out (to the Jaguar speedometer). The unit is also adjustable to fine tune for various tire sizes and differential ratios. It is smaller than a pack of cigarettes and can be easily mounted nearly anywhere under the Jaguar dash.

Please see the "V8 Conversion Price List" page for current pricing on these various components