Spark Plugs

[Mitsumark]

Fellas..Ok I have a fully ported 368..I installed a set of NGK Iridium TR71X gapped at .50..The car seems to hate them as my slight misfire has gotten worse immedietely..I pulled them back out and reset gap at .35..Still no good.. I'm suspecting I have a weak coil and plan to pull the plenum.I would like to try one more set of plugs before I do so.. What would be the recommended non iridium plug to go for?I would like to go 1 step colder than stock..Again this is for a nicely modded 368 91Z running on a Marc Heibeck chip..I know I've been a pain these last few days,however Atleast I can get my post count up so I don't look like the noob that I am..

[scottfab]

Seem Max in Malan, Italy was having the same issue with NGK Iridiums.

[lbszr]

FR1LS is one step colder if you want plugs with crush washers. They work good for me.

[Paul Workman]

AC Delco 41-602 copper plugs are good for at least 10k miles.

Plug aging is insidious by nature. And, because of the cost, some want to wring out every drop of use from a set of plugs. However, the 41-602s are cheap enough and since plugs are easy enough to change on the LT5, their advantage over "super-duper pricy plugs" is I can pop in a fresh set every season without causing a ripple in my beer money.

I (and others) in "FBI" land use them and have no issues with them - work perfect way past 7200 rpm and 500 chp; and I get north of 26 mpg at 70 mph (cruise).

FWIW,

P.

[XfireZ51]

I think I suggested NGK BKR6Es @ .035". I have found these plugs to be of the right heat range for a modded motor. You could search the site. I may have pics of plug cuts I have done.

[scottfab]

Originally Posted by Paul Workman

AC Delco 41-602 copper plugs are good for at least 10k miles.

...snip...
P.

I just may have to go that way because I tend to take plugs out each year for various reasons anyway. And at $1.41 ea with $0.50 rebate per plug right now at rockauto the time is right. That's $0.91 ea !!