4 replies to this topic

[gazza01]

Hi all.

 

I would like to know what gap I should be setting Iridium plugs at with elec ignition. NGK Iridium IX.

They have arrived with pretty much no gap at all.

Thanks.

 

1330 engine a+

Standard re-curved metro dizzy.

Edited by gazza01, 22 February 2014 - 09:44 AM.

[Gadgets]

25 THOU (Hack saw blade is 25 thou)

[Gr4h4m]

I have always stick my ix's straight in they have always Been pre gapped. If your stuck I can check the spares in the garage tomorrow

Edited by Gr4h4m, 22 February 2014 - 10:37 AM.

[MUD&ROX]

Iridium plugs are designed NOT BE GAPED! if you must make sure you do NOT touch the center electrode or porcelain as they are very fragile

[tiger99]

Taking proper care as above not to damage them, they should be set to the same gap as any other plug for your combination of engine and ignition system. The use of a miniscule quantity of iridium does not change the behaviour of the spark in the slightest, only affecting plug life. Most Minis are designed to run with 25 thou gap, which as said is the thickness of many hacksaw blades. Some, including my old City E with 2.95 diff, in a partly successful attempt to get better torque, were gapped wider, 35 thou, if I remember correctly, using a ballasted coil. (In that engine, the recommended Bosch plugs lasted about 200 miles, I had to use a Japanese equivalent, which were ok for 10k or so, and I have never, ever used Bosch plugs in anything since.) 

 

If your engine is the original for your car, or a reconditioned one of the same type, the gap stated in your handbook (if you have one, most will have been lost many years ago) will be the correct one to use. If your ignition system genuinely generates a higher than normal voltage, then the wider gap is appropriate, and will make a small improvement to performance and/or economy, if your coil, leads, rotor arm and distributor cap are in good condition. (The maximum voltage depends on the plug gap and compression pressure, too high and the spark will go somewhere else other than in the plug gap.)

 

Too narrrow a gap will cause poor running, bad economy, etc, while too wide will do all of that and overstress the coil too.