Spark Plugs

[pontiacgp]

I have an NGK plug problem and they havn't been in very long so I'm going to thro in a new set of AC Delco's. I usually run the 45 plug but I just thought of something. Since I have no EGR the heat in the combustion chambers is higher so I'm thinking of going down in the heat range to a 44 plug. That might allow me to run a little more advance without pinging. Any thoughts from you guys?

 

[RITTER]

Sounds like a good start to me 8) Do you run a tapered plug or washer seat :?:

I am starting with R43 plugs in my engine. Then I will make any changes if needed.

 

[chevy2480]

I always ran 43's. Not until recently did I relize there are a couple 43' there is a commercial ac delco 43 has a thinker electrode. I think it cr 43 iforget have to check but thats what i am running next.

 

[RITTER]

They don't offer a CR43 though, just a CR43T (which is tapered) If you're running the older GM heads, you need the flat seat type :idea:

 

[Longroof79]

Steve,
What problems are you encountering with the NGK's? I've also been having a problem, and I'm also using NGK's. But I think I have it pinpointed more towards a wire. I have the same plug that seems to foul. It sure seems like a firing problem. It's #2 plug. I hear the car not firing on all cylinders. The #2 seems to be wet and dark.
Would any of you guys know how many ohm's per ft. I should be looking for? I recall seeing it in an old issue of Car Craft, but forgot what was said.
#2 is the longest wire of the bunch. The set is a few years old. They're 8mm Taylor Spiro-pros. It does have continuity, but I'm wondering if there's too much resistance in that one wire.
I could also tell when it starts misfiring. #2 header tube is not as hot as the others.
I like the NGK's. They have good header clearance and I usually don't have any problems with them.

Sorry, I didn't mean to hijack this thread.

 

[pontiacgp]

Sounds like a good start to me 8) Do you run a tapered plug or washer seat :?:

I am starting with R43 plugs in my engine. Then I will make any changes if needed.

It's a taper plug, I picked up some R44 LTS and I see what they do. The NGK's I was running were equal to an 45 plug. The problem with the NGK wasn't the plug after all. There was a hole in the heat sleeve that I never realized was there and that hole lined up perfect with the header so one of my moroso ultra 40 race wires needs to be repaired. It was arching with the header... :|

 

[Bonnewagon]

Steve, what timing are you running? Without EGR you should be running old school pre-EGR timing specs, which is a LOT less than stock 1980's timing. I like AC Delco plugs too, but when I need to go down colder I like Champions since they offer a much wider heat range. For example my stock RBL17s can go all the way down to RBL13's. Jack, does this help? (low = good, high = bad)


A conventional plug wire has a resistance of 10,000 to 15,000 ohms per foot of length--if it's measurably higher, the wire probably is bad. An absolutely failed wire will have a hairline break somewhere, and the resistance will be infinity.



MSD Ignition 8.5mm Super Conductor (40-50 ohms/ft)
Accel Thundersport (150 ohms/ft)
Taylor 8mm Spiro Pro (350 ohm/ft)
Aurora ignition wire set (400 ohms/ft)
Vitek Performance Cables (their web site does not mention resistance, but John Monnin measured them at about 800 ohms/ft; the label under Vitek's braiding says "Magstar Gold 8mm High Performance S-4 Stainless Steel Mag Wire" - thanks John!; Magstar wires are manufactured by Wiretec)
Wiretec Magstar Gold (800 ohms/ft as measured by John Monnin)
NGK Resistor Spark Plug Wire Set (2600 ohms/ft)
Mitsubishi factory wire sets (3000++ ohms/ft)
Car Quest brand wire sets (3000++ ohms/ft - Thanks to Bret for measuring these wires.)
Magnecor KV85 (6000++ ohms/ft)

 

[pontiacgp]

I have my initial timing set up for 9* and then I have my distributor advance curve set up for and additional 25* to max out at 2500 rpm....I did have the advance curve set to hit the max at 2000 rpm but this set up seems to work better

and Jack, you didn't hijack the thread....every bit of info on wires and plugs is helpful

 

[custom442]

my thought process typed out, so dont mind if I'm typing what you're thinking. combustion pressures are mainly affected by compression, rpm, AFR, ignition, and heat dissipation (main source of change is spark plug heat range). Let's pretend we don't change compression, rpm ratios vs spark, or heat dissipation (plugs). We 'should' keep the same stoich AFR by removing inert EGR gases simultaneously burning more fuel, this increases combustion temps by increasing volumetric efficiency. Since we have a larger volume of fuel/air to be burned we want to burn that not necessarily earlier or later overall but at the point VE increases.

EGR is only active on high manifold vacuum. So mechanical advance should be similar timing as stock, the centrifugal advance will not change from your previous setting. The efficiency question comes in where vacuum advance needs to be tuned, since you now have a higher volume of fuel = higher combustion pressure/temp you're going to need to move the spark forward on vacuum to tdc. Meaning you want to reduce vacuum advance overall because you've increased the VE/power per cylinder air charge that in turn increases the flame front velocity. Because the front is moving faster it reduces combustion time during high manifold vacuum.

So your thinking is somewhat correct, increased VE of part throttle driving could warrant a step cooler plug, but then combustion pressures would have decreased enough with the vacuum timing correction I doubt a different plug is needed. I would not go with a step cooler in order to increase advance to create a situation where I needed to protect against further detonation.

You're not gaining much by the cooler plug, in fact you may not be gaining anything because detonation occurs mostly at higher rpms, and neither VE nor full centrifugal spark should change on WOT high rpm. Not to mention the amount of overall mech. advance needed to increase combustion temps to the point we're talking about generating a need for a cooler range plug could actually decrease power (now if you feel this is untrue for your engine, cuz every ones different a better option is to run more total mech. with water/meth injection on the top end).

The better option for something like this is keep the current stock heat range plugs. Retard only your current vacuum advance about 4-5 degrees overall. If with this setup you notice no knocking or detonation at peak torque (wherever that may be on your engine) then you're in the clear and stock plugs will work just fine. Since you already stepped down one plug, then you're pretty much covered for anything detonation wise. efficiency wise adjust the vacuum advance dizzy. Hottest plug without detonation = longer life and more complete/full spark on a street car, fouling becomes a non issue. hope that helped clear some things up.