69 z sparkplugs
 

Does anyone know the correct ac spark number for a 69z? thanks

AC Delco Acniter R44 is the go to plug for Z/28 as far as I know. Many people run the hotter R45 and some have tried the colder R43 plug but they're usually not well suited to the street and tend to foul.

I got a set of R43 off eBay a couple years ago and last year got a couple sets of R44 from another member here on the forums.

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If by "correct" you mean what it came with from the factory, that would be R43.

Most guys run R44. They don't seem to foul as easily. Some guys claim the R43 helps keep detonation down.

Checked my notes and the assembly-line correct R43 plugs should have 4 equal green bands and the word 'ACNITER' on the porcelain.

I have a box of R43N and the outer carton says "New" Acniter. Anyone know the difference between the R43 and the R43N?

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R43 is a 3/8 reach plug (3/8 inch of thread).

R43N is a 3/4 inch reach plug.

In and out of the trailer or car show I would go to 44's or 45's John. 44's if you are going to drive it around. Take those cars out to the Curly Top or to get a newspaper on Saturday mornings Johnny. Its good exercise for them!

Honestly, I like my Holley's. They burn good winter-summer with no real issues.

----Big believer in Autolites in a driver!......Bill S

I had to use 45's with my x-ram. I am with Bill on the autolites, they do not foul as quick.

I run Autolites in mine. I see better results with the heat range changes. I tune mine with a wideband to dial the carb in nearly perfect. Living up here at 5,000 ft I routinely drive the car down to sea level so I tend to tune where I find a happy spot for both.

I found the Autolite 86's work best. Equivalent to ACR45S (extended tips). They stay clean up here at 5,000 ft running just slightly rich 12.5-12.8-ish AFR's, and low to mid 13 AFR's at sea level. I stagger jet the carb for best results. Wife drives it daily up here and routinely gets 14.2-14.5 mpg with it in stop and go traffic.

I run NGK's, and seem to never foul. Based on the responses I may switch to Autolites next time.

There is,I went from Autolites to NGK.
I'm staying with NGK.

Yes Steve, NGK's are good. Japanese made I believe. We run them in my fathers 760hp Pontiac. Just have to keep in mind the NGK heat ranges work backwards, meaning the higher number is the colder plug.

What's NKG's equivalent to AC 45?

XR4, that's as hot as they get.

That's equivalent or close to the R45S AC plug which is an extended reach plug (electrode and ground strap extend into the chamber slightly more) which is better for flame travel.

I don't believe NGK makes the shallow plug that would be equivalent to an AC R45 (no S in the part number) We always called those oil burning plugs because the electrode and ground strap were very shallow and not out in the path of the chamber.

I ran the XR4's in my Z for about 2,000 miles as an experiment. Worked fine up here at 5,000 ft. But had #2 and #3 showing a tad rich, which runs off the left front corner of the carb. I wanted to go to a warmer plug but NGK doesn't make one hotter. So I tend to believe the XR4's may be closer to the R44S heat ranges because those plugs worked similar. I already had the carb stagger jetted for best power so I decided to switch to Autolite 86's, which are as hot as they go and equivalent to R45S. Been clean ever since.

My L-78 Chevelle takes AC R43T from the factory.
The NGK equivalent is stock #2771 UR5.

Is that a mistype??

The "T" in the AC line means that's a small 5/8 taper seat plug. The "U" in NGK line is also the small 5/8 taper seat plug.

I wouldn't think that's a typo twice??

I ask because shouldn't L78's be a square port large gasketed 13/16 plug head?? Or did GM go to the small plug on L78's in 1970??

Sorry about the confusion,the T is correct.
And yes,because it's for my 1970 L-78 Chevelle.1970 LS-6 & LS-5 used same.
I know this is about a '69 Z/28 camaro,just wanted to add my usage for posterity.

Cool, learned something new. I always thought the big plugs were used up through 1970.

All my BBC stuff is 71-72 that uses the small plug. I figured the change was 1971.

The T stands for taper....the spark plug itself is tapered to match the taper of the spark plug hole in the head where the plug screws in and there for does not use a crush ring to seal tight to the head like an R43 or R44 does.

Yes "T" is taper seat, which as far as I know also coincides with the small 5/8 plug. I've never seen a taper seat large 13/16 plug. Those have all been gasketed from my experience.

The "S" at the end stands for "extended tip" which has the electrode and ground strap extending slightly more into the combustion chamber which promotes better flame prognation. Performance oriented tuners generally switch to the extended tip plugs for better burn.

The S (extended tips) are all that I use in my stuff and actually if you cross over any AC R44 (standard tip) plug to an Autolite or NGK, you automatically get the extended tips with these plugs even though you're crossing a non extended tip AC plug.

Autolite 84-85-86 is the large 13/16 gasket plug with extended tips and the NGK XR4-5-6 are also 13/16 gasket plugs with extended tips, as well as the UR4-5-6 that Mr70 is using.

If you compare the stock AC R44 or R45 plug to any Autolite 85 or XR-UR NGK, you'll see right away the difference in electrode and ground strap distances.

Hope that helps.

I ran AC R43T's for 9 yrs in my 69 Z and that thing ran like a top!
It was 99.9% original/untouched except for a set of headers and it ran really strong and very smooth. Always started up with ease as well.