Lets Talk heat range of spark plugs

I have been running the NGK R5673-10. My combo is a 521 BBF naturally aspirated. This plugs have been the only plug I have had since the dyno
pulls and tuning a few years back by my engine builder. Everything I read says these plugs are meant to be used in high boost/nitrous applications.

Would a set of #9's or 8's be better suited for a drag race application? How would this effect the tune up/ performance of the engine. I have not been
having trouble just curious as to the difference.

Any and all comments are welcome.

What do they look like?

That is a colder plug than what most people run NA.

That is the coldest plug offered. I ran it on a cast iron head with 14-1 c/r and it was fine. I tried a -9 and it showed some overheating. For an aluminum head and or less compression ratio , I would look at a hotter plug.

It's an Aluminum Headed engine around 13 to 1 compression.

I'm just not that good at reading plugs.

I run that plug with alinum heads 17-1 compression and a 500 shot.

The 8 works in most NA setups.

+1 I would use a -8 on an aluminum head with 13-1. The aluminum head sucks heat out of the plug far better than an iron head does and is the reason a warmer plug can be used.

Truly,

I can't recall any color on the plugs they stay pretty clean.  I have not spent too much time racing the last few years, so trying to
remember.  It seemed that it started a little hard, maybe a hotter plug would help it fire quicker on start up.

I remember that i would warm the car, on a old set of plugs and then put fresh plugs in before my time runs.

I think I got -10 because that's what the shop had and i never tried any other plugs..

Thanks for the help.

cool40 wrote:The 8 works in most NA setups.

Agreed

How would these compare to a Autolite Racing plug? How do these numbers cross reference?

away wrote:How would these compare to a Autolite Racing plug?  How do these numbers cross reference?

Something like an AR12

away wrote:How would these compare to a Autolite Racing plug?  How do these numbers cross reference?

we had a new set of autolite racing plugs that would hardly run. Searched for the problem a while before figuring it out. They looked like a bad monday morning job or autolite may be buying from china? Replaced with ngk-9 and it sounded normal again.  so we wont be useing autolite plugs anymore.   https://2img.net/h/i206.photobucket.com/albums/bb173/nbjuljetta02/Spark-Ref.jpg

cool40 wrote:

away wrote:How would these compare to a Autolite Racing plug?  How do these numbers cross reference?

we had a new set of autolite racing plugs that would hardly run. Searched for the problem a while before figuring it out. They looked like a bad monday morning job or autolite may be buying from china? Replaced with ngk-9 and it sounded normal again.  so we wont be useing autolite plugs anymore.

Did you run a plugfax on them....could be a salvage title deal

Lem Evans wrote:

cool40 wrote:

away wrote:How would these compare to a Autolite Racing plug?  How do these numbers cross reference?

we had a new set of autolite racing plugs that would hardly run. Searched for the problem a while before figuring it out. They looked like a bad monday morning job or autolite may be buying from china? Replaced with ngk-9 and it sounded normal again.  so we wont be useing autolite plugs anymore.

Did you run a plugfax on them....could be a salvage title deal

these were new,in the box,OEM autolite racing plugs but looked about as quality as a champion!

I was also told that Auto-lite plugs went to china! So you are probably right.

So what would the recommendation be for a naturally aspirated bracket car methanol injection. TFS street head

Thanks

away wrote:I was also told that Auto-lite plugs went to china!  So you are probably right.

So what would the recommendation be for a naturally aspirated bracket car methanol injection.  TFS street head

Thanks

ngk #8 is what I run.

We also use #8 in N/A stuff and even in some small nitrous stuff

NGK Spark Plugs R5671A-8 - NGK Racing Spark Plugs

Autozone part number 4554?

Is this the part number?

away wrote:NGK Spark Plugs R5671A-8 - NGK Racing Spark Plugs

Autozone part number 4554?

Is this the part number?

Yes

So,

Here is a follow up question.  I normally run the -10 with 87 Carb Jets.  If I switch to the hotter -8 should I go up a jet
or two to accommodate the hotter plugs??????

Fuel should have been right regardless the plugs temp.  Most noticable diffrence will be start up.  Crisper

Well I finally was able to make a few passes and the car ran pretty consistent.   Here is a picture of the #5 cylinder after my first time run. These are the #8 NGK's.   I did have to idle  a bit on the way back to the pits.  Any and all comments are welcome.

Heat range looks good.  Fuel line ok, maybe a little rich.  I see a few specs, might want to drop timming a degree or two.  Few oxide of n20 fecs.

Timing is at 31 or 32 degrees. Thanks for your response.