Don Terrill’s Speed-Talk

Anyone here have experience reguarding iridium plugs compared to conventional plugs in a non emissions engine ? Can you say other than plug life, does the Iridium have any advantage in a mildly modified street engine? Thanks

All threads I have read on the subject say no. However...

Yeah, maybe some dyno or track info would be helpful.... I was using NGK fine wire "gold" plugs in my vintage land speed race bike...I switched to NGK Competions plugs, a conventional style with a cut back ground electrode and the bike ran the same speed or even a bit better...

So far as I know, the iridium is intended to reduce electrode wear; as in the original factory-installed iridium plugs in my Trailblazer went 160,000 + miles; and weren't misfiring when I ripped them out 'cause I couldn't take knowing they were that...experienced...any more.

This is a total non-issue in a performance application. Without the feedback fuel injection, they'll deposit-foul before going as many miles as the electrodes are good for.

Waste of money to put iridium plugs into a performance non-emissions-compliant application.

They last longer in applications using an HEL type of ignition.
MSD systems tend to wear out conventional plugs faster then the others but that said I have seen in marine
engines switching them to the new style iridium plugs the timing needs to get backed up 2 degrees as the spark timing
seems to be faster with the iridium plugs over the conventional plugs using a marine ignition system.

Yes they are more money and if you have an engine with an oiling issue they are a waste of time over a older design plug
as they foul just the same but with an HEI system they will last much longer making them worth the outlay
over changing 2-3 sets more cost effective if you are paying a tech to replace them.

The fine wire should require less voltage to fire, which at a minimum would give more reserve spark.
On the other hand, years back when GM had a road-race series for stock Corvettes, the Motorsports manager told me the (late eighties) engines consistently lost a few HP with iridium plugs. I suppose it could have been due to the SA issue ProPower mentioned...

ProPower engines wrote: ↑Fri Nov 01, 2019 4:02 pm They last longer in applications using an HEL type of ignition.
MSD systems tend to wear out conventional plugs faster then the others but that said I have seen in marine
engines switching them to the new style iridium plugs the timing needs to get backed up 2 degrees as the spark timing
seems to be faster with the iridium plugs over the conventional plugs using a marine ignition system.

What exactly makes a marine igntion different other than maybe the advance curve?

Truckedup wrote: ↑Sat Nov 02, 2019 6:48 am What exactly makes a marine igntion different other than maybe the advance curve?

Generally marine engines are under constant load at a fairly steady throttle. Depending on how the cooling system is set up, they may not operate at the higher temps a car will either, then add in rough water, sudden directional changes, etc.... In other words they live a rough life compared to most other applications. The ignitions themselves really aren't much different except they are certified for marine use. It's more about how it's used than what it is... if that makes sense. Marine builds are a different animal from other stuff

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What exactly makes a marine ignition different other than maybe the advance curve?
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Its about load on the engine.
Picture your truck towing a trailer all day long wide open up hill in 2nd gear. In larger boats thats what the load compares
to in most marine engine. Getting the timing curve correct is a big deal and in lots of cases the new style plugs make a difference of 2-3 degrees on the advance side cause they are less resistant to voltage making them fire faster.
Controlling cyl. temp is what its about and in street or race cars the duration of run time can affect the amount of timing
being run. A short burst with more timing in most cases will not destroy an engine but a long haul will because
of several other factors but if there is too much lead then they melt and self destruct really fast.

A race engine with too much timing will have issues. A boat with too much timing same thing happens it may just
take a bit longer because of cooling but the cyl. temp will get too high and then its over.