P-Mag Iridium Gap?
 

I got some Iridiums from Rock Auto at under $7 each (received in 3 days to CA) and wondered what the gap should be - same as the regular electrodes? Is there any trick to gapping them, seems it would be prudent to be delicate with that little electrode?

Same gap and same adjustment procedure as assigned to your compression ratio with the regular auto plugs. :)

I generally use 28-30 thou, this is usually the gap they come with.

Iridium gap
 

Walt,
Did you say you're running 9:1 pistons in your Superior IO-360? If so, is there a particular plug your engine seems to like better since your running dual electronic ignition? My "standard issue Denso plugs" are currently gapped at 32 thou. Sounds like that's a bit much,,,, would you agree? I'm running dual Plasma III ignition. I just received eight new Denso iridium plugs to give a try, but I want to test out the standard Denso plugs first to see if I can tell the difference when I switch to the iridium plugs.

Chad

9:1 should be ran @ .026 ... most others .032

I runs stock 8.5 pistons. As the plugs wear the gap increases so keeping them a little tight to start allows for some wear. You do not want the gap to get to large as it causes stress on the coils.

Klaus's recommendations are as follows (and I have no reason to think different):

Engines normally timed at 25 degrees BTDC:
These are normally engines with compression ratios less than 8.7:1. Gap spark plugs fired by the CDI to .032"-.040".

Engines normally timed at 20 degrees BTDC:
These are usually engines with compression ratios of 8.7:1 or higher. Gap spark plugs fired by the CDI to .026"-.035".

Thanks guys.
Should have mentioned they are used on a P-Mag in a 150HP O-320.

Engine Timing
 

Walt,

I'm running 9:1 pistons in a Superior IO-360 engine. I'm also running dual Lightspeed ignition (Plasma III's). The dataplate on my high compression IO-360 says to time it at 25 degrees. This is contrary to Klaus' recommendations in his installation manual. Regardless, I've always set my mags and now the Plasma III systems at 25 degrees (initially) and thus far have had no indication of detonation or high CHT's. Any suggestions on where I should set my Iridium plug gap? I think I'm running at .025 currently with no obvious issues.

Chad

I prefer to keep plug gaps on the small side, a smaller gap means less stress on ignition system components (coils) plus it allows for some inevitable plug wear. So .025 is fine IMO.

You're "probably" ok with the 25 deg timing but this is a bit of an unknown, if you're a careful operator and have full engine monitoring you should be fine, if you're not or don't then the 20 deg would be a more conservative setting.