Spark Plug advice for AFR 185's

[jcode68]

I did a quick search, but couldn't find a quick answer. What spark plug/heat range are you guys using for AFR 185's? Their website spec says "spark plug starting range Autolite 3924". Is this an ideal heat range or what is the best way to determine what is right? I am on the East Coast in MA and do not drive the car in cold weather. Thanks in advance for any education.

 

[2bav8]

Lots of variables here...
My 347 is close to 11:1 compression and I have recently started to use the 3923 with good results. The 3924 worked well but the strap was showing signs it was too hot.


http://www.dragstuff.com/techarticles/how-to-read-plugs.html

 

[jcode68]

Thanks for the link. I haven't fired the engine yet, and am looking for a good starting point. Engine is 347 stroker with 9.5:1 compression, using the Crane Hi6S ingition with PS91 coil. I notice you live in AZ, which is really different climate than me. I will probably try the 3924 unless someone gives me information otherwise. Thanks to the link you sent, I will be able to read the strap and change accordingly.

 

[thehueypilot]

I'm running 225's and I crossed to a NGK 7924 (Jegs 739-R5672A-10) which is two steps cooler. One step cooler is R5672A-9 (NGK 7405). This is the web site I use to cross different brands: http://www.sparkplugs.com/results_cross.asp?pid=3922&crossManID=33&mfid=

 

[jcode68]

Thanks for another good link. I think I have a starting point and will read the plugs after a few miles to see if I need to adjust. I'm not running high compression or using nitrous, so I suspect I will be ok.

 

[66HertzClone]

Until I intalled EFI, my engine is almost exactly like yours. I am running NGK plugs.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=NGK-5724&N=0&autoview=sku

 

[SoCalCruising]

I run 3923s in SoCal. My motor is right at 10:1. This plug was recommended by the supplier of my heads/cam.

 

[jerry S]

the right plug depends on your CR. Edelbrock emailed this to me last year in response to my same question as yours.

 

[jcode68]

the right plug depends on your CR. Edelbrock emailed this to me last year in response to my same question as yours.

This confirms the 3924 is a good starting point given my comp is 9.5:1. Thanks for the post.