Hello All,

Here is what I have....1969 Camaro. The engine was built by the prior owner so I do not know alot about the internals other than the cam card & specs he told me. It's a 350 Mouse, around 10.5:1 compression, (I don't know what type of piston) Competition Cams .292 duration with a .524 lift if I recall correctly..... I know it's a hydraulic cam. I have a Richmond ST-10 trans, Moser 12 bolt w/ 4:11 gears. The carb is a Holley 750 dbl pumper mech sec. The ignition is a MSD Pro Billett 85551 distributor w/ the magnetic pick up. I have the MSD Blaster 2 High Vibration Coil. I replaced the junk MSD 6-AL Box on Monday with the MSD Digital 7 Plus Box. I have Edelbrock Performer Bolt on Aluminum Heads.

Here is the deal. The old plugs have only been in there about 6 or 7 weeks. They are NGK R5671A-8, V Power Racing Plugs. They have about 75-80 miles on them tops. This car is not a race car, it is a street car. The old plugs look carbon fouled maybe because the 6-AL box was not getting a hot enough spark and having intermittent issues. But still for the plugs to look that bad? After 70-80 street miles and only 6 or 7 weeks?

The NGK plug # above has a heat range of 8 according to what I saw on this link on Summit http://store.summitracing.com/partdetail.asp?autofilter=1&part=NGK%2D4554&N=700+115&autoview=sku

I think that spark plug is overkill for this car. Most have a heat range of 4 or 5 for street applications. This has a heat range of 8 which means it produces a really hot spark. The prior owner was making it into a race car but I have slowly made this thing back into a street crusier with some oomph. Are the NGK Part # R5671A-8 spark plugs overkill for my application? If so what would you guys recommend for a spark plug with this engine, cam, heads & ignition? Or should I stick with what I have? :confused:

P.S. Just in case anyone is curious, the carb is a little over 1 year old and has 300 miles on it. I also replaced the cap & rotor about 6 months ago and they have about 175 street miles on them.

Thanks!!

SSG&H aka Greg

AC Delco R43S.

Heat range of a spark plug has nothing to do with how "hot" a spark is produced; heat range is how hot the plug insulator runs in order to continuously burn off combustion deposits.

Don't know what heads you have or which type of plugs it takes (gasketed or tapered-seat), but a good starting point for a street heat range is equivalent to an AC 44 or 45, depending on conditions and driving style, and adjust from there. Any other plug brand can be cross-referenced from the AC heat range.

:beers:

8 is not hot. And like John said that only tells you how hot the center electrode stays due to how much porcelain nose it has ... to burn deposits not to affect firing.

AC45 is what I run in my ZZ4

I tried R45's in mine and had fouling problems, went back to the 43's and they are clean, I'm sticking with 43's.

I tried R45's in mine and had fouling problems, went back to the 43's and they are clean, I'm sticking with 43's.

How does that happen? 43's are two heat ranges COLDER than 45's. :confused:

Here it what everyone might be missing: Gap! I use Autolite 85/86, and for some reason my built 350 didn't like the AC43's. Anyway, no matter what brand you use, gap at a min of 40, and I find that 45 is optimal. MSD needs this kind of gap to excel! Some guys go up to 50, but again, I found 45 is optimal, and we have a fairly similar set-up. If you're currently gapped under 40, you'll see, feel, and hear the difference immediately after trying this.

How does that happen? 43's are two heat ranges COLDER than 45's. :confused:

John, it may be that the 43's will foul out pretty quickly also, I think I may need new valve seals.

South Side : I run -8's heat range in my drag motor so there to cold for the street I run NGK 5724-8 ,I can't remember if lower # is hotter or colder ,with NGK. AC higher is hotter ,good luck and always Happy Motoring