spark plug recomendation?

[karfever]

I am going to replace the plugs on my 90 ZR-1. Wha do you guys reccomend as far as manufacturer and number? Thanks

 

[Demps]

AC Delco Rapidfire #9 gapped at .035".

ted

 

[karfever]

Darn it TED! I read the previous posts about plugs and installed Rapid fire #5 at factory gap. Poor choice?

 

[Demps]

Nope, not a bad choice at all. One of my cars have the #5 the other has #9. Can't really tell the difference. The #9 is for a little more spirited driving. I think the factory setting on a 90 is .050". If the car idles poor or has tip in stumble (give it gas while a gear hi or it chugs or misses in a range) the gap is too wide for your current ignition system. I've had #5s in my car for a little over a year now. 3,000 miles and no complaints. I'll change them with #5s the next time and post any differences.

ted

 

[Wegone]

I have RapidFire #5 gapped at .045 been in there for about 15K miles...Ted, is the #9 a hotter plug??

 

[Demps]

Here's some interesting info that I didn't even know:

http://www.idavette.net/tech/acplugs.htm

 

[karfever]

Pretty interesting report Ted. Thanks for the posting. So in your valued opinion, is there anything to gain by switching from the #5's to the #9's? The car seems to run very well with the fives.

 

[Demps]

In my humble opinion--in daily driving there is little to no difference with a well tuned/maintained/fairly stock car and good gas (at least 92 octane). I gapped mine at .035 and have no problems. Some folks have gapped them at .050 and have gotten a rough idle or hesitation at tip in. The overall health of the ignition system will play a factor as well. "If it ain't broke, don't fix it." There are times that you don't realize it's just not right. I wouldn't go to #9s until its time for a tune up.

ted