JMatlock88

I am currently running AC-Delco FR3LS (which have been superceded I now learn). I am planning to finally spray, beginning with 50 and eventually jetting up to 150. I am running afr 195cc heads, 10.7:1, 350. The nitrous is entering through an NX shark and a crane TRC-2 is hooked up to retard with activation. Please recommend a plug (prefer ac-delco standard style)! If you need any other mod info, just ask. Thanks!

12 Sec GTA

I run NGK plugs in my car.. IIRC, they are the UR-6's.. Just a little colder than stock.

92camaro

I also run a NGK plug I have not had any problems with them. I would run an NGK #9 plug with the 150 shot. I can get you the complete part number tonight.

strokeronthesause

autolite 3933 race plug up to a 350 shot 3932 anyshot!!!!!!! neat plugs the ground stap is real low and and comes cut right out of the box.

B4Ctom1

JMatlock88 nice car, how did you work out the hood room issue for the HSR and what headers did you end up going with?

JMatlock88

Here is a good link to check out how I clearanced the hood. The headers are ceramic coated Hooker Supercomp Longtubes. Thanks for the nice comment!
https://www.thirdgen.org/techbb2/sho...hreadid=163688

12 sec gta, what does "IIRC" mean?

92camaro, yes that would be helpful!

strokeronthesause, please expand on..."neat plugs the ground stap is real low and and comes cut right out of the box"


So far we have:
NGK-UR-6
NGK-#9
Autolite 3933
Autolite 3932 (350+ HP shot)

Thanks for all of the replys! Keep 'em coming!

B4Ctom1

Im pretty sure that in AC the lower the # the lower the heat range ("cooler"), If it isnt please somebody tell me. I see you have the FR3LS which breaks down as follows:

• F - Fine line 14mm thread with 5/8" hex
• R - Resistor
• 3 - Heat range #
• L - Long reach: 3/4" (19mm) for a plug with 14mm thread fineline
• S - Extended tip

I usually go two heatranges cooler and run nice gas for a nitrous application. This I guess would be a FR1LS (if lower truely is cooler). This BTW is the plug used in your 98 Chrysler FWD products with the 2.0L (Neons, sebrings, etc.) stock. The plug two ranges higher (FR5LS) is the plug for 89-92 5.7 TPI cars stock. So you may want to consider your current compression, and the fact that you may already have a plug that is cooler than might be needed. I'm not sure about thread and size compatability but I always ran the R43TS plugs myself.

JMatlock88

Yep, that ac delco description is exactly right according to my research. I was planning on going with a FR2LS, one step down, because I am already 2 steps cooler than a TPI plug. However, the FR2LS is not currently produced.

I am looking for an NGK equilevent to this plug along with some real-world examples with people running nitrous on similar combos.

Also, how does compression ratio effect desired spark plug heat range?

B4Ctom1

some people as they approach like 11 to 1 go a range cooler some even more, for the same reasons as they do for nitrous. It is not as critical with EFI N/A (my opinion).

bjm323

FR2LS cross-references to:

NGK Part #BCPR5ES or NGK Stock 6130
Autolite: 3924

Free Bird

iTrader: (1)

That's what I use. Cheap plug that does the job.

89gta383

iTrader: (5)

The FR2LS and FR1LS are getting harder to find. The autolite 3926 is the same size and is the stock heat range = FR5LS. The 3924 and 3923 is equal to the FR2 and FR1. I get the autolites at wal-mart. Anything colder in an autolite and you have to get the non-resistor short-electrode plugs like the sauseman mentioned, the 3933 and 3932. Nobody stocks them though, they will have to order them. Napa can get any plug I want. Use this chart for a cross-reference:

http://www.clubplug.net/acdelco_ngk.html

JMatlock88

Thanks for that great link. Confusing though how the chart gives a different NGK cross-reference part number than bjm323 mentioned for the fr2ls. What gives? This is what has made this selection process so cumbersome.

I'd like to move the thread into a friendly comparison of the three brands mentioned: Autolite, NGK, and AC-Delco. Let's try to keep the "well I've used this for 20 years" out and stick with product design information, material longevidy, controled testing, etc. There might not be a superior plug, but I'd like to bring in some information might prove useful for readers.

Thanks for the replies so far!

I realize the archives are full of spark plug debates. I'd like this one to focus on nitrous use.

bjm323

Here is where I got my numbers from.

Sparkplug Interchange Guide

You need Excel to view it.

89gta383

iTrader: (5)

Damn! That's an even better cross-reference chart.

25THRSS

Will going down a heat range effect daily driving when off the nitrous?