QuickVet

i am starting to change my plugs right now and was wondering what gap most of you are running? I have the ZZ4 heads, if that helps.

thanks,
AARON

PRNDL

.035

What is your iginition? I believe some of the electronic ignitions with a highpowered coil (Specifically thinking of Pertronix) allow you to use a wider gap if you want. MJ

dgruenke

I don't know if the heads make a difference, but most cars run about .044. :chevy

QuickVet

ok thanks for your help. I put them in the car at 40 because i wasnt sure. we see how it runs tomorrow. thanks for your help.

if im way off let me know. I can still change em again ;)

the ignition is an MSD HEI. thanks

Paul 75 L82

With the MSD HEI you could probally go as wide as 60.

QuickVet

anyone know the stock gap for the zz4?

PatsLs1vette

i thought i saw it was 35 some where not sure ill look again
Spark Plugs:
MR43LTS Gap .045, AC FR5LS Gap .035, Rapid Fire #5 Gap .045. http://www.sallee-chevrolet.com/Chev...ckV8s/355.html



[Modified by pats406nitrovette, 9:20 PM 4/5/2002]

mountainmotor

The same as any small or large block Chevy that uses a HEI Distributor so the same as your L82 was when stock

With a hot ignition system the rule of thumb is wider gap for town use/mild performance.For racing in high compression engines,narrow the gap to prevent misfire and or blown out spark at high RPM.

A Vertex Mag works best at.022 with a cold plug

QuickVet

guess i will be safe at 40. but then i will change em for more gap later.

4_inch_Bore

according to Chilton's...
.035 all 1963-1974
.060 all 1975-1976
.045 all 1977-1984

QuickVet

that is if your not modified correct? when you have new heads you gotta go by the plug that fits that head, correct?

mountainmotor

Quote:
"060 all 1975-1976"

That has since been changed back to .045

Quote"
"that is if your not modified correct? when you have new heads you gotta go by the plug that fits that head, correct"

Correct !





[Modified by mountainmotor, 9:09 PM 4/5/2002]

fontking1a

I've found that widening the gap in spark plugs seems to make the car run better with this crummy fuel that we must use. My '69 427/435 calls for a .035" gap but I run mine at .045". At .035" the car wants to run a bit rich and just by opening the gap in the plugs, it runs like a champ. I've been doing this for almost 20 years and so far, no ill effects.

73Ken73

I have been told by engine builders, racers, and performance part store owners that a .035 gap is good no matter what ignition you have or what mods have been done.

Vetterodder

The main consideration when deciding the gap is the ignition being used, the compression ratio, and the anticipated rpm. Most electronic ignitions allow for a wider gap, which is usually benefitial at lower rpm but too much gap can be a problem at high rpm. The instructions for my MSD box recommended gaps from .040 - .060 depending on cr, higher cr's using less gap. If you don't want to experiment, set `em at .045 and you should be ok.