The Definitive Rover V8 Engine Knowledge Base for Range Rover, Land Rover, TVR, Morgan, Marcos & Classic Cars Running Rover V8 Engines


Power loss? Ö what power loss?
Many would say engines running with a dual fuel system have less power than before conversion to duel fuel. The truth is not so clear cut.

  • The lower calorific power of LPG is partly compensated for by more complete combustion.
  • The higher octane of LPG allows engine and ignition modifications with obvious advantages in power.

This is not however the bottom line on the subject as LPG does indeed have the added advantage of being a much higher octane fuel. To understand this it is important to realise that over the years our petrol engines have had their compressions lowered and their timing advance amounts continuously reduced year by year to cope with ever-lower fuel grades.

A good example of this is when we were told all fuel was to be changed to unleaded about 5 years ago, the short term solution was to alter (reduce) your engineís ignition advance yet again. However, with LPG being 110 octane the exact opposite is true and can be used to your advantage. While most petrol engines are happy enough to run on LPG, the truth is, this slower burning fuel needs a bigger spark voltage and an advanced spark timing (usually around +10deg) otherwise by the time the combustion process is completed, this 10deg loss would effectively reduce each power stroke by the same amount.

Basic ignition issues
LPG can indeed be as economical and powerful as fuel with the main issue/improvement with the ignition timing and spark intensity.

Due to the slower flame front of LPG, Either upgrade to a Mallory dual point as above (carb type only with nearly double spark output and about 6 degrees of added internal timing).

Or fit our unique new retard by advance system (electronic ignition types only). We have just released this device which replaces the original ignition amp on your distributor (we can also supply a brand new distrib utor if required) and allows you to set base timing to 18 degrees, thus giving a healthy 38-40 degrees of advance when on LPG. This will be the answer to all LPG prayers, and, whatís better, when running on petrol it retards the ignition back to std 8 idle - 28 deg. @4000.

Added spark Intensity
As well as the ability to offer the most appropriate timing for your engine when running on LPG, another important function of our ignition amp upgrade is that it delivers a far higher spark voltage. Unlike others , we do not tell you to reduce plug gaps or other strange methods, indeed we actively encourage a V8 spark gap to be opened to 0.8-to 0 9 mm Spark intensity is so much better that it will show up the worst in poor quality plug leads.

Magnecor leads
Any weakness in your ignition system will cause a misfire under load, and the consequence to an LPG powered engine is normally a backfire, this in itelf is not a big problem but certainly is a compromise you donít need to live with. When it comes to ignition leads you can consider them to be not disimilar in importance to perhaps speaker leads. Would you fit your £5000 Hi fi with £20 speaker leads? While we donít want to encourage you to go wild and buy gold plated ones,
there is a big difference in signal loss and quality between high street plug leads and quality ones.


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