Spark Plug Gap
 

OE gap is 0.05. I'm wondering what the best gap for a stock ZR-1 ('90) w/ NGK iridiums is... I hear a lot of different opinions from the GM for plugs...

Edit: Maybe this should be in the tech section.

Re: Spark Plug Gap
 

I don't know that this will help as I use the stock GM replacement plugs, the 402's, in my '90, but I use 35 as my gap as per the FSM.

Re: Spark Plug Gap
 

first off be very carefull when cking the gap on these plugs . i use a ring gap tool and go until it just bearly touches . i found with these plugs that 45 thou is max for me .i settled on 40 thou for the ngk. hope this helps

Re: Spark Plug Gap
 

OE specwas 0.05. then they said use 0.035 as your doing. for the rapid fires they said 0.045. so its confusing.


But, NGK's come at different factory gap. And a different gap for each type of plug they make for the LT-5. so i was wondering what was best for the NGK iridiums.

So, 0.04 for the NGK iridium?

Re: Spark Plug Gap
 

yes ,being an old drag racer i have gotten used to reading plugs and at .40thou. they seem to burn the cleanest . jmho

Re: Spark Plug Gap
 

keep in mind that you do not have a high performance ignition system - So your coils can only produce so much voltage to jump the GAP - the bigger the gap the more umpf you need - So I would stay between the .035 - .040 gap. The plug is not the issue - Its the ignition system we have.

Don Yoakem
91 - #267
Dark Red Met.

Re: Spark Plug Gap
 

i agree . its the coils that limit the gap

Re: Spark Plug Gap
 

1990 has .035 from the factory.
I wouldn't go more then that with stock ignition..

Pete

Re: Spark Plug Gap
 

pete , just wondering why is the 90 different than the other years ?

Re: Spark Plug Gap
 

It's 1990-1992 have .035 factory specs.
1993-1995 are .050 factory specs.

I think for idle quality and they went with those 100,000 mile spark plugs,not 100% sure.
Pete

Re: Spark Plug Gap
 

so would you suggest 35 for every year ?. guess i am going to try 35thou at the strip on fri . i have maybe mistakenly so used 40 -48 thou as gap .it will be fun to find out if it helps at all . thanx for the info pete :thumbsup:

Re: Spark Plug Gap
 

THe reason for the change in gap is that the ignition system received a boost. That's why the gap increased. It was not because of the plugs. If you change your coils to MSD - you could go to a slightly larger gap. The MSD coils have a bit more voltage out put then the factory coils. So if your current gap is .035 I would leave it there or go a go slightly tighter to .032. Coils can work easier.

Best of luck

Don Yoakem
91 #267 Dark Red Met.

Re: Spark Plug Gap
 

Brad,yes i would go .035 on any year Z.

Don, you are the man .032 is perfect, like you:)
I agree with Don on this.

Pete

Re: Spark Plug Gap
 

I am just a humble supporter of making things go faster with less work. :wink: