Spark plug question.....

[Vette73]

Looking to change plugs soon on my 91...Basically stock except for headers, exhaust and Marc's chip..

I was going to give Marc a ring, but I figure I would ask the members...
Which is a good plug to use? I also read somewhere instead of a .035 gap, you could go with a .050 gap for a little increased performance..

Any suggestions?

Thnx.....JW..

[secondchance]

Originally Posted by Vette73

Looking to change plugs soon on my 91...Basically stock except for headers, exhaust and Marc's chip..

I was going to give Marc a ring, but I figure I would ask the members...
Which is a good plug to use? I also read somewhere instead of a .035 gap, you could go with a .050 gap for a little increased performance..

Any suggestions?

Thnx.....JW..

I have been using NGK Iridium plugs gapped at .50.

[QMCMSS]

I used NGK part # 3690. This plug is one range colder than stock. I gapped them at 45. This setup solved a high rpm miss i was experiencing. The car pulls great now to 7000 simple fix that really improved performance. Pulled a plug after about 50 miles to have a look and it was burning beautiful. Wish I could claim this idea myself but I think this is pretty much the setup I found on one of Marc's pages.

[Paul Workman]

I follow Pete's suggestion and go with the AC Delco 41-602s. Pete has run the 1/4 mile to well over 7600 rpm (over 129 mph in 3rd gear) with them, and I've had NO issues with them either. AND, at about $2 each, instead of running them to 10k or so (typical of standard, copper core plugs), they're cheap enough to instal fresh ones ever 2-4k miles for less than a tank of gas.

Out of habit, I inadvertently gapped the plugs at .35 instead of .40 or .50 the last go-round. She runs like a champ, even way past 7000 rpm. Why pay more?

[Hib Halverson]

I use the Denso IT-22 in my LT5.

I've been using that since the Denso Iridium Power design was introduced in the early 00s.

I've had two sets in the engine since then. They have phenominal durability.

The IT-22 is two ranges colder than what's currently recommended for the LT5 and one range colder than the original LT5 spark plug the FR-1LS.

Performance advantages to the IT-22 are the fine wire iridium center electrode and the u-grooved, cut-back ground electrode.

Paul has a key point about the cost of standard ACD plugs vs some of the Iridium products, but I don't necessarily cater to the perspective that cost is the main issue with spark plugs. Afterall, if I was really concerned about the price of spark plugs maybe I shouldn't own a ZR-1. I am more interested in the ultimate in performance along with the durability of iridium center electrodes and that's why I use the IT-22 in my LT5. In fact, I use the in our two Z06es, too.

[Blue Flame Restorations]

Originally Posted by Paul Workman

I follow Pete's suggestion and go with the AC Delco 41-602s. Pete has run the 1/4 mile to well over 7600 rpm (over 129 mph in 3rd gear) with them, and I've had NO issues with them either. AND, at about $2 each, instead of running them to 10k or so (typical of standard, copper core plugs), they're cheap enough to instal fresh ones ever 2-4k miles for less than a tank of gas.

Out of habit, I inadvertently gapped the plugs at .35 instead of .40 or .50 the last go-round. She runs like a champ, even way past 7000 rpm. Why pay more?

Agree 100%

[Paul Workman]

Originally Posted by Hib Halverson

I use the Denso IT-22 in my LT5.

I've been using that since the Denso Iridium Power design was introduced in the early 00s.

I've had two sets in the engine since then. They have phenominal durability.

The IT-22 is two ranges colder than what's currently recommended for the LT5 and one range colder than the original LT5 spark plug the FR-1LS.

Performance advantages to the IT-22 are the fine wire iridium center electrode and the u-grooved, cut-back ground electrode.

Paul has a key point about the cost of standard ACD plugs vs some of the Iridium products, but I don't necessarily cater to the perspective that cost is the main issue with spark plugs. Afterall, if I was really concerned about the price of spark plugs maybe I shouldn't own a ZR-1. I am more interested in the ultimate in performance along with the durability of iridium center electrodes and that's why I use the IT-22 in my LT5. In fact, I use the in our two Z06es, too.

Hello Hib! (Great to see you at the Gathering, BTW)

Actually, when taken into account the life expectancy vs. initial cost of the plug; standard vs. 'rare earth', the cost is about the same. The life expectancy of a standard plug and their cost is proportional to the life/cost of most(?) 'rare earth' plugs.

However, the initial outlay for a new set of standard (ACD) plugs is under $20. AND, in light of actual performance (in the LT5) vs. manufacture's claimed performance (in who knows what application), "time slips are always better than hype, at least in my book. Towit: (see link>) demonstrated performance in the LT5.

Note: IIRC, this "FBI" ZR-1 was/is a stock-bottom 350 cid LT5 with full porting, custom phasing (claims 474 hp at the wheels), Jeal LT headers, B&B exhaust, X pipe, and 3.45 differential gear. The rev limiter has been bumped way "up there", but doing the math is quite revealing!!