Quote:
Originally Posted by jss06c6
This has been discussed in other posts, but wanted to add some pics and history. My '91 is ported, full SW exhaust (headers to tips) and tuned.
I installed NGK TR7ix plugs gapped at .050" about 2,500 miles ago. Had dead coil, so replaced it. Wires were good. Had a slight, but noticeable stumble at low rpm acceleration. Decided to pull plugs. What I found shocked me. Only 2 of the 8 plugs remained at .050. Others were about .058. However #7 and #8 were .068! As others have indicated, batch fire and iridium don't seem to like one another. Moved to NGK 4177 (TR6) copper core. Gapped at .045".
Engine is back to 100%. Picture of #7 attached.. Attachment 13329
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Interesting "head scratchier".
Pete Polatsidis put me onto
AC/Delco 41-602 copper plugs some 8 yrs ago and I've never had a reason to switch (to another plug)! And, the fact that they're only about $2.00 ea. means I can install new plugs every season* (less than 3k miles or <4.8km) and gapped at 0.040" (1.016mm).
*Pete ran his ported 5.7L LT5 into the low 11s on those plugs too. What's not to like about inexpensive plugs and cheap enough one can run on essentially "new" plugs all the time (i.e., one isn't tempted to put up with deteriorated performance while trying to wring out the last 3-4k miles (~5-8km) on pricey rare-earth plugs...Just sayin!)