onefynryd

Haynes Repair Manual says to gap spark plugs to these specifications:

Ignition system

Spark plug gap

1997 and earlier

3.4L engine 0.045 inch

3800 engine 0.060 inch

5.7L engine 0.050 inch

1998 and later

3800 engine 0.060 inch

5.7L engine 0.060 inch


So the Question is.... I have a 99 z28, no n20, I was thinking of getting NGK's. Do I gap them at 0.060 or 0.050? All I read is everyone says to gap them at 0.050 inch.

Greed4Speed

iTrader: (7)

I'd stick w/the .060.

Smaller gap = smaller spark kernal = less spark to ignite the gas

I know the big deal about running aftermarket ignitions in older cars was so you could get a larger gap to help w/ignition.

cueball

really you need to experiment with that, because every car is different
for one, plus if you have done any mods you probably changed the
compression ratio and thus you need to change the gap accordingly
the higher the C/R the stronger the spark you need, because higher
Compression can actualy '' blow '' the spark out.

so i would start with .050, and go up.
it is kinda hard to check the spark out side of the combustion chamber
like on the side of the block, because pressure effects the spark.
so i would start with .050, and test hooked up to the plug wire and to a good ground and go up, and when you find the brightest big blue spark, and then
go 3 to 5 thousandts DOWN to compensate for compression.

(example: best spark at .055 so gap down to .052, to .050)

hope that helps

onefynryd

thanks guys!

Fred99LS1

If you get the NGK TR 55's, I can say .050 works pretty good on a stock engine up here in NYC, Fred

NC Guy

Set whatever plug at .055 on a mild street motor. The hassle to pull them just to regap ain't worth the time.