to iridium or not

zedsn · 03-23-2016, 11:20 AM

Would it be beneficial to use NGK iridium spark plugs or just regular NGK non resister plugs when using pertronix with a MSD box and MSD coil? Is there a benefit other than longer life or not too much to justify the much extra cost? I did email MSD about my plug options using the MSD box but they have not returned my email.

RedCoupe · 03-23-2016, 11:26 AM

All you really need are plugs that last for the valve adjustment interval, and standard copper NGK plugs do just fine at those intervals.

cmcfaul · cmcfaul's Garage

Was in an auto parts store and they had a display where you turn the crank. Regular and Iridium plugs wouuld both spark. The Iridium spark was much larger than the copper.

Chris

john walker's workshop · 03-23-2016, 11:47 AM

I like them for dirty running MFI/carb engines that darken regular plugs. Everything else gets regular NGKs.

RSTarga · 03-23-2016, 01:08 PM

I moved to EIX from ES NGK's for my MFI. I never had a problem with the normal ES's but the original plugs were 265P21 platinum and these were closer to original spec.
If you have a fouling problem I think the Iridium cleans itself quicker.

zedsn · 03-23-2016, 01:16 PM

Well I have weber 40 carbs and my car has not been on the road yet so figure they will run on the rich side and would I tend to foul the regular NGK plugs a lot quicker? I want a no fuss motor and figure iridiums would be worth it. Would you guys recommend them for a hopped up engine?

Dpmulvan · 03-23-2016, 02:06 PM

Can't say for a 911 but I always ran iridium plugs in my motorcycles and was very happy with them.

zedsn · 03-23-2016, 02:33 PM

Regardless of which plug I use what should I gap them running MSD box, hot coil and pertronix?

Biff · 03-23-2016, 03:10 PM

They last forever. They helped my old mfi run better without going thru constant plug exchanges.

tirwin · tirwin's Garage

Quote:

Originally Posted by zedsn

Regardless of which plug I use what should I gap them running MSD box, hot coil and pertronix?

MSD normally recommends going up .005 over factory gap and then increasing in .005 increments until you find the optimal gap. Take a look at the MSD manual or the FAQ on their website. I'm pretty sure it states the exact recommendation.

zedsn · 03-23-2016, 04:00 PM

Thanks and will do.

RSTarga · 03-23-2016, 04:10 PM

I wouldn't regap the iridium, once you see them you'll see how difficult it would be to do this right.

emac · emac's Garage

I have used Nkg regular plugs for years
Normal gap and last for at least a few years with no issues
Ernie.
I did try a slightly hotter plug a few years ago but found no difference. Had a slight miss and bought their wires- problem solved

T77911S · 03-24-2016, 03:41 AM

Quote:

Originally Posted by zedsn

Well I have weber 40 carbs and my car has not been on the road yet so figure they will run on the rich side and would I tend to foul the regular NGK plugs a lot quicker? I want a no fuss motor and figure iridiums would be worth it. Would you guys recommend them for a hopped up engine?

run a hotter plug.
the real need for hot plugs is due to the idle circuit.

I did a test
I ran a bosch w3 in my 77s on a trip and they looked very good after the trip. they were even used out of my brothers 930.
they were black when driving around town. I should have a 5-7 in there.

if you track it run a little colder plug on the track.

tobluforu · tobluforu's Garage

I have run bosch supers, the three prong ones from way back, those worked great in the car. Run ngk coppers now, but I'm going to try iridium's this summer in my mfi car.