hey john spark plug help/choice please

[chpcamaro]

hey john or anyone i'm just looking for input for when i go nitrous any input on what plugs to start with bbc with 15.1 using 175-200 shot i was looking at the ar3924 but i have read that champion and ngk are more forgiving i do like autolite but i want your input
thank you
rob

oh and i will be running c16 or higher input on this is welcome to

[John_Heard]

At that shot level I'd start with the NGK R5671A-8 or the equivalent Autolite AR3934.

If you miss the tune up a mile and have too much heat in it you'll melt the ground straps off the NGK's before you would the Autolites.

[chpcamaro]

thank you john also where is a good place to buy them i was going to call autozone, pepboys and napa because for some reason they don't come up on there online search
thank you again
rob

[John_Heard]

Need to have one of the other guys chime in here, I buy mine at a small auto parts store here, not one of the chain stores. I think Autozone carries NGK but you may need to ask the "racer guy" there if they have those plugs on the back shelf somewhere. They might not be up front on the racks.

[ProCar]

The 9's (NGK) just might be a little better choice; that's a chunk of compression. Besides, 175-200 turns into 250-300 fast, we are racers after all. A 572 can take a 38 pill from a fogger without blinking. Jeff Prock said it real well, 1 hp per inch is nooo sweat. Basic, but surprisingly accurate. C 16 is a great fuel. Happy New Year Mr Heard!

[John_Heard]

I don't disagree with the -9's Patrick, I have ran -8's quite a few times on shots that size range and they worked just fine, however those were on a little bit lower compression engine. Oh and Happy New Year to you as well Mr. Budd..

Rob - per that other discussion, -11's are way to friggen cold IMHO for that shot. If you tune it down to where it's showing lean on that cold of a plug I think you'll be in a danger area, but that's just my opinion, I don't have the experience those other guys do. However you'll probably see it fall off big time in MPH also before you get to that point.

[chpcamaro]

i was planning on trying the 10's at first do you think i should start with 9's john. i do value your input so thank you for responding to all my questions.
and happy new years to all
thank you
rob

[chpcamaro]

hey john were you referring to the yellow bullet post i think your right about the 11's being to cold so i am going to start with 10's on the dyno and see which way to go from there. steve and monte over there seem to want to run a really cold plug now when i ran nitrous in my sbc i never ran that cold of a plug because when i started out i took there advice and went to a colder plug (3 steps)and to be honest it ran like crap so i jumped back to what i was running before the nitrous and the car came alive and never had one problem so i'm sure about this super cold plug thing.
but i never ran this much compression with it so this is why i have been asking so many questions and honestly it won't stay at 175 come on we all want more but i will take it slow plus my car is only certed for 8.50. i figure i should be there very easy i have a few friends with less then i do and we all weight the same on the scale and they are running 8.20 on a 200 shot with a progressive controller.
so any ways i'm going to start with the 10's and see how it turns out on the dyno hopefully next week.
thank you once again
rob

so are you beyond?

[John_Heard]

The 10's or 11's won't hurt anything and they will be less prone to being a hot spot in the cyl no doubt, the problem is how they'll affect your tune up decision making process because they're going to be harder to read at that tune up level. They will show a fatter condition than what you would see with a hotter plug, if you're on the dyno and have AFR to assist you that will be very helpful. I guess what I'm saying is go as cold as you want, but be aware that the colder plugs are going to read fatter than what you would expect, and in my opinion if you lean it out on that shot size to only show a wisp of fuel down inside, it's going to be awful lean. Be careful...

At the track, -11's will be a pain in the butt unless you own a 4 wheeler or golf cart to pull the car to the lanes and back up the return road. Also be prepared to use a set of -7 or so warm up plugs. -10's and -11's don't like slow speed operation.

Yes, my nickname on YB and several other boards is "Beyond", my company name is Beyond Engineering.

[chpcamaro]

ok i'm starting to understand what your explaining now and it's making sense now the more i think about it i was trying to be safe but safe can be accomplished 2 ways and i think i like your out look on this so now i feel NGK R5671A-9 might be a good starting point correct me if i am wrong but the 9's should make it easyier to read so i can see if i need to go hotter or colder and the 10's would show fuel because it won't be hot enough to completely clean it's self and give me the false reading that i am rich or good but in reality i could be close to being lean did i understand that right.
than you
rob

sorry for all the questions but hopefully this will also help others out

[John_Heard]

Good, I'm glad what I was trying to get at makes sense. Sure the 9's would be ok, and no doubt easier to read than -10 or -11's... you get what I'm saying. There are lots of ways to go about tuning a nitrous engine and they can all be right, some of them are harder to understand than others but the main thing is make lots of power but not hurt anything. Few of us can afford to break these things.

Sometime we need to get Mr. Budd to explain how he goes about doing it, because I'm pretty sure he does it starting from the lean side of the bell curve of cyl temp if I remember correctly. There are many ways to skin a cat, some of them will leave you with fewer scratches than others.

[chpcamaro]

i picked up 2 boxes of NGK R5671A-9 today so it's a done deal lol and what a relief thank you once again john after doing alot more reading and talking with a friend that tunes a lot of big nitrous cars for the psca he agree with you on your plug choice
thanks
rob