http://www.dsmtuners.com/threads/spark-plug-faq.233421/

According to this i should go 7 or 8... and a 28 gap

I was also recommended these which we do use at the track sometimes but with 600plus hp cars. http://m.oreillyauto.com/mt/www.oreillyauto.com/site/c/detail/NGK8/4554.oap?pt=N0608

The spark will start to blow out. I'd stick with the 6's but get the ones without the protruding tip, they should be fine. I used 7's up to 29 psi then went to 8's.
I know people will probably disagree or say I'm wrong, but I don't gap my plugs I check them out of the box and as long as they are all the same I just drop them in.

fastfred said:

The spark will start to blow out. I'd stick with the 6's but get the ones without the protruding tip, they should be fine. I used 7's up to 29 psi then went to 8's.
I know people will probably disagree or say I'm wrong, but I don't gap my plugs I check them out of the box and as long as they are all the same I just drop them in.

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Wow. Man thats the basics of any car. You gotta gap the plugs. To the op i would use the ngk 7s.

jimsgsx said:

Wow. Man thats the basics of any car. You gotta gap the plugs. To the op i would use the ngk 7s.

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Thanks.. i was thinking i just barelu outgrew the 6s..

fastfred said:

The spark will start to blow out. I'd stick with the 6's but get the ones without the protruding tip, they should be fine. I used 7's up to 29 psi then went to 8's.
I know people will probably disagree or say I'm wrong, but I don't gap my plugs I check them out of the box and as long as they are all the same I just drop them in.

Click to expand...

This is bad ive never came across and issue when they come out of box but i always check them and ive rand around 26-27 gap and have always been right there but i always check

Also i always just drop in the ngk bpr7es and car loves it

I run br7es gapped down to 20 at 26 psi on a 20g. Solid pulls and no studder.

jimsgsx said:

Wow. Man thats the basics of any car. You gotta gap the plugs. To the op i would use the ngk 7s.

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My car makes 500 wheel horsepower on those ungapped plugs. My mustang does too. Everybody has there ways and opinions and that's ok. I prefer to keep the end of the plug even and not bend it. If I check a plug and it's off or not the same I take it to my parts department and get another one. We gap plugs on my dads race car, we also change them every time we go to the track. Overrated in my opinion.

To each his own.

I would step down 1 heat range. If you find that your getting a lot of knock, I'd suggest trying the non projected plugs, but be advised that they effectively retard the timing by 2-3*. They will reduce the possibility of preignition though because of the reduced hot spot.

fastfred said:

My car makes 500 wheel horsepower on those ungapped plugs. My mustang does too. Everybody has there ways and opinions and that's ok. I prefer to keep the end of the plug even and not bend it. If I check a plug and it's off or not the same I take it to my parts department and get another one. We gap plugs on my dads race car, we also change them every time we go to the track. Overrated in my opinion.

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Is your dyno sheet in your profile current? Hope not, because I wouldn't consider 421 anywhere close to 500.

bastarddsm said:

I would step down 1 heat range. If you find that your getting a lot of knock, I'd suggest trying the non projected plugs, but be advised that they effectively retard the timing by 2-3*. They will reduce the possibility of preignition though because of the reduced hot spot.

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Im getting 2* retard in the 5500 and up range.. it was a thought that came to me from my honda build... but that car was 470 to wheels on 1000cc injectors. We had to step it down again when i added 1850s.. just wasnt sure what the dsm would want.

What kind of plugs do you run? NgKs you can tell if your heat range is decent by how many threads are discolored. I don't remember the specifics but about 3 threads with the cad playing burned off is about right. I ran BR8ES making 600whp and did step down to 9s and saw a decrease in ks activity. I am on E85 and about 35psi. I ran autolite #63 for a long time and up to about 500whp

Pretty much I would run as cold as possible without sooting up the plug.

bastarddsm said:

Pretty much I would run as cold as possible without sooting up the plug.

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The honda runs ngk 8s(62mm borg turbo) i was blowing out spark on everything else. I cant see the talon on 18 to 20psi on 14b needing 8s. Ill try 7s first. Just want to kill the top end knock without reducing timing..

Try some non projected plugs and give it a couple degrees back.

CrackedDSM said:

Is your dyno sheet in your profile current? Hope not, because I wouldn't consider 421 anywhere close to 500.

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Its obviously not current. It's ok to disagree, everybody does things different. I do what works for me on my cars. I don't know what the big deal is? Check the plugs out of the box run them, gap them, whatever you want. Everything I suggest is something I've tried not something I've heard or read, that's why I come here, to leave/gain real world experience for/from others. Not to read useless comments that take up space b/c I haven't got around to updating my profile.

Really nothing to argue about, plug gaps are not set in stone. Some car like bigger gap and other like smaller one. Gaps from a new set of plug out of the box are pretty consistent ~.28-.30, if that worked, who's to say it's wrong.

you should be fine on 7 plug with gap somewhere under .28.

Im picking up ngk racing 7s... i think 8s will be too cold with my set up. Im only around 250hp as a guesstimate from dsmlink