chevy guy here, problem with "spark blow out"

[parish8]

my set up is a ls1 based 6.0 motor with a t76 and nx kit. i am up to 16psi and a 75shot. 18psi has the miss too.

i really dont know if i am blowing out my spark or i have some other problem. i have a miss up top, especialy when i push it(nitrous or cut out open with lots of boost). i have tried several diferent plugs and they all seem to make a diference.

i have new msd wires, no help

older tr6 plugs gaped at .035 or so missed 6000, then 5800, then 5600, missed worse as i put miles on them.

new tr6 plugs helped but it still missed above 6000rpm

gaped tr6's to .030 and no change

tried some autolite 104's(i think) helped a little but not much

then some ngk br7ef at .025, completely fixed the problem, i was shifting at 6500rpm no problem. 600miles later starting to miss again. i pulled a plug and the gap didn't open at all. here is a pic of the plug.

i am running leaded fuel. i monitor my tune almost constantly, no knock retard, fueling is in the mid 11's at wot and 13-14.5 the rest of the time. truck runs great other than that top end miss. on the dyno i stoped the pull at 6000rpm and wasn't at my peak hp yet so i think i am missing out short shifting it.

any ideas?

 

[oehm]

Glad to see you made it over here Parish. Do you get a miss at high RPM's with low boost levels (10 psi or less)?

 

[azgn]

leaded fuel fouls plugs really quick with a tight gap.......600 miles is way too long....change 'em every time at the track and I think the prob will go away

 

[parish8]

nope, after doing a few hours of research tonight it looks like "lead fouling". something about the deposits need to be burnt off slowly but that isn't how it works with my set up. i am either puting around or WOT. i am going to work on my part throttle fueling and get it a little closer to 14.7 and probably just slap in new plugs anytime i goto the track.

 

[azgn]

there ya go!

 

[parish8]

Originally posted by azgn
there ya go!

yep, there i go, it is nice to have somone post up and say the same thing. i feel prety confident this will fix my problem.

 

[motorhead]

I bet you enjoyed the coverage in HRM this month, eh?

Congrats... that is a crazy 4X4 you got there.

 

[Reggie West]

You are blowing out the spark on the plugs.

I have seen it on Buick V6s with big turbos too. The cure was exactly what you said. Gap the plugs at .025 and you are good to go.

I very highly recommend using 116 octane gas on that beast when you are at the track.

When you are tuning the motor you are going to find that motors such as yours may not like A/F ratios of 14.7 to 1 very much. Even at idle they seem to like 12.5 to 1 better , just give it what it wants and they will make gobs of power.

Neat truck no matter what. Keep us posted.

 

[vicious6]

That is one awesome truck man, keep us posted on how it is doing!

 

[V6 Beast]

I am not familiar with the plugs you are using, but on high HP Buicks, we have issues with Plat. plugs. So if you are using a plat plug, you may want to try a copper plug gapped at 25-28.


Sully

 

[parish8]

Originally posted by V6 Beast
I am not familiar with the plugs you are using, but on high HP Buicks, we have issues with Plat. plugs. So if you are using a plat plug, you may want to try a copper plug gapped at 25-28.


Sully

my latest plugs are the ngk br8ef, it is a copper plug that comes pre gaped at .025.

one person told me the iridums took longer to lead foul than the copper plugs. anyone know if this is true?

 

[Otto J]

Ive been running the Autolite Racing plugs, P# AR3932, Which is a bit colder than those ngks i believe, I use them with the gap out of the box, and with over 600 street miles and 18 passes (in one day )they are still firing like a champ and i was running 30# of boost all day.Look into them as they use a wide ground cut back electrode
Otto

 

[Randy Greenoe]

Originally posted by parish8
my latest plugs are the ngk br8ef, it is a copper plug that comes pre gaped at .025.

one person told me the iridums took longer to lead foul than the copper plugs. anyone know if this is true?

I read an article where Kenny Dutteweiler said that he picked up 150 h.p. on a turbo V.W. using Iridium plugs. He said that with the Iridium plugs he could run higher boost levels without blowing out the plugs. Honest I am not making this up!!