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- C4 ZR-1 Technical Postings (http://zr1.net/forum/forumdisplay.php?f=9)

- - sparkplugs (http://zr1.net/forum/showthread.php?t=27395)

Keep in mind that virtually all plug recommendations in catalogs, regardless of manufacturer are, IMO, too hot.

When the 1G LT5 was in final validation back in the late 80s, GM and Lotus specified the FR1LS spark plug, which was in the ACDelco #1 heat range. That offered best performance in all normal street driving duty cycles.

Right as the car was reaching dealers, because of concerns about "pre-delivery plug fouling" and its effects on customer satisfaction, the spark plug spec was changed to the FR2LS, which was the one range hotter #2 heat range. The only reason GM did that was to avoid warranty problems with any pre-delivery spark plug fouling which might occur and addressed some customer complaints of new car with fouled plugs. When ACD started publishing spark plug data, it listed the FR2LS and all the other plug makers followed that lead, i.e." NGK lists their 5 heat range, Denso lists its 16 heat range and so on and so forth.

No one in the C4 ZR-1 community needs to be concerned with pre-delivery fouling and use of the 2 heat range plug, unless their ZR-1s are never driven normally and are subjected to duty cycles such as frequent starts-without-warm-up, trailered car-show use, short trip street driving only use with no high-rpm or high load use.

Anyone who drives their ZR-1 normally...ie: seldom or never any starts without-warm-up, should go to a colder plug. Such as:

ACD #1 heat range
NGK 6 or 7
Denso 20 or 22.

The reason you want a somewhat colder plug is that hot plugs make the engine more prone to detonation under high-rpm/high-load operation.

For the last 15 years I owned Barney, my 500-hp '95, I used the Denso IT-22 exclusively. It worked very well on the street and in mild racing applications. Before that I used the NGK 7 heat range.

The NGK TR5IX is too hot a plug unless the car is a show car and never is driven normally. You need at least a TR6.

Quote:

Originally Posted by Hib Halverson (Post 256432)

Anyone who drives their ZR-1 normally...ie: seldom or never any starts without-warm-up, should go to a colder plug. Such as:

ACD #1 heat range
NGK 6 or 7
Denso 20 or 22.

The reason you want a somewhat colder plug is that hot plugs make the engine more prone to detonation under high-rpm/high-load operation.

For the last 15 years I owned Barney, my 500-hp '95, I used the Denso IT-22 exclusively. It worked very well on the street and in mild racing applications. Before that I used the NGK 7 heat range.

The NGK TR5IX is too hot a plug unless the car is a show car and never is driven normally. You need at least a TR6.

Hib, I can return the TR5IX plugs which are arriving today. You mention above that I need at least a TR6, I can also get a TR7 that you have also used. So which one do you recommend. I drive just under 5,000 per year.
I now have 68,000 + on the 94, the plugs were changed by a PO @55,000 miles. The plugs that are in there are AC 41-963
Thanks for the info.....appreciated.

Factory heat range is usually ideal for the low speed emissions testing, but maybe I will try an alternative at one range cooler someday because you can definitely get some pinging on CA 91 octane gas in the summer.

Quote:

Originally Posted by Roadster (Post 256457)

When I used NGKs, I used the 7 heat range. Of course, back then the TR plugs didn't exist in the NGK line but, yeah, if you are partial to NGK, then you need the TR7.

Quote:

Originally Posted by Hib Halverson (Post 256538)

When I used NGKs, I used the 7 heat range. Of course, back then the TR plugs didn't exist in the NGK line but, yeah, if you are partial to NGK, then you need the TR7.

Sounds good to me, because the TR7IX are on the way. Returned the TR5IX.
Thx, appreciated.....

Quote:

Originally Posted by mike100 (Post 256464)

Regardless of what plug you run, you are going to get spark knock on 91-octane gas because GM calibrated for 93.

When I had my 95, because I was at sea level, the only time I never saw KR at WOT was when it was really cold out. Once it warmed up outside I'd start to see KR. If it was a hot day I'd get a consistent 5-7 deg. spark retard.

What the colder plug will do is keep the spark plug from making the knock situation worse, if the detonation incident occurs under wide open throttle/high-load conditions.

For what it's worth...

41-602s in Pete's Green Monster

https://www.youtube.com/watch?v=SFNFOhGGlR4

41-602s after one year in my 500+ LT5, gapped at .035

http://i185.photobucket.com/albums/x...psrpb9nrx1.jpg

Quote:

Originally Posted by Paul Workman (Post 256572)

For us un-mechanical folks, what am I looking at? Spark plugs obviously, but are these good looking plugs for a year worth of use? Were they fouled or anything, and what does gapping do? I'm wanting to change my plugs, would they need gapped or is that for modified engines?

They look near perfect

Sent from my XT1585 using ZR-1 Net Registry mobile app

Quote:

Originally Posted by rush91 (Post 256573)

Some photo comparisons if you scroll down a bit.

https://www.autohausaz.com/html/spar...lug-wires.html