j.j.&s.racing Posted February 23, 2014 Report Share Posted February 23, 2014 which plug is better for sport mods. ar 12 or ar 133. Link to comment Share on other sites More sharing options...
JUMPSTER93 Posted February 24, 2014 Report Share Posted February 24, 2014 I have always ran the ar133 plug in a sport mod. Seems to work well. There are a few different ar plugs. Ar 131 is a colder plug, and ar 135 is a hotter plug. All fit the sbc. Link to comment Share on other sites More sharing options...
jwmbishop Posted February 24, 2014 Report Share Posted February 24, 2014 Depends. What color is the car? Is the driver left handed or right? Seriously though - the best plug is whichever shows the heat range line in the very center of the curve on the ground strap and yeilds a clean electrode during WOT. Two identical long block engines with differing tune (manifolds, headers, cam, cam timimg ign timimg, fuel strategy etc) or fuel can easily use two different plugs. Even if both are installed in a sport mod. On a new engine I would always use the last plug I found on 2-7 (so I know it worked at least) and swap the number one a few times with the same plug of different ranges (one range up and two down) until I found the right one. No good sense in buying four sets of 8 just for testing when 4 individuals will tell you the story and then you only have to buy 7 more of the right one. And the "test" plugs can be boxed and used again... sometimes. edit to add clarity: Heat Range = Ground Strap, the ground strap indicates the heat-range of the spark plug. If the "color" of the ground strap "changes" too close to the ground strap's end, (which is above the center electrode), then the heat-range is "too cold" , meaning that the strap is loosing heat too quickly to the base ring, and is not able to burn off deposits until near its end. If the "color" of the strap changes near where it is welded/attached to the base ring (last thread ring), then it means that the plug heat-range is "too hot", because heat is not being tranferred/cooled from the strap to the base ring quickly enough !!!! The strap might begin to act like a "glow-plug", eventually causing preignition and/or detonation later on. Proper heat-range is when the "color" is at the half-way point on the strap, neither too cold or too hot. This only works perfect when you shut off at WOT and coast in! Even an idle to the pit box will defeat accuracy. Link to comment Share on other sites More sharing options...
jbarber19 Posted February 26, 2014 Report Share Posted February 26, 2014 Thanks Bishop. That's some very interesting info. Do u have an opinion about running higher batt voltage & wider plug gaps ? Link to comment Share on other sites More sharing options...
jwmbishop Posted February 26, 2014 Report Share Posted February 26, 2014 Thats a good idea with the "stock" hei. However if you have changed the module, coil or both to a high perf the secondary voltage is already kicked up. Increasing battery voltage then only makes for a faster drop off when voltage decreases - so an alternator becomes required rather than just optional. Many folks think that the alternator uses more power than is gained. In some cases that's true but without a dyno its hard to tell. Increasing the gap gives good results at lower RPMs - at higher RPMs when coil saturation time gets shorter, and cylinder pressure increases - the increased gap can defeat the purpose as the spark "scatters" at a lower RPM and the flame front has a harder time forming as the spark itself actually makes less heat. Some of the guys that ran drag race and circle swore by increased gap because they saw the drop in their ET. However a drag racer starts from 1000 RPM and goes to 6000 ish so the average RPM in the race is 3500 - circle race RPM is 3500 to 6500 for an average of 5000. With any Multiple Spark (capacitive discharge) you can increase the gap with less concern of loss in firing "heat" From MSD: The spark plug is the point in the ignition system where electrical energy is converted into heat, consequently, the larger the gap the greater the amount of heat available to light the air/fuel mixture. However, too large of gap combined with increased cylinder pressures can put excessive pressures on the initial voltage needed to ionize (cross) the gap. Finding the optimum plug gap for your application is best determined by experimentation because there are so many engine variables to consider. An MSD Ignition Control has enough output power to consistently fire wider spark plug gaps on a performance engine. As a starting point, follow the engine builder or manufacturer’s recommendation for the plug gap. With that, you can experiment with increasing the gap until the best performance is found. As a rule of thumb, it is recommended to increase the plug gap by .005” - .010” followed by testing and tuning. Keep in mind that larger spark plug gaps also place increasing demands on the secondary portion of the ignition system including the distributor cap and rotor, coil wire, and spark plug wires. They should all be in top condition and checked periodically during the race season. Remember that electricity takes the path of least resistance to a ground so if the gap is too large the spark may short to another point with less resistance. Added: Which brings up the point that a plug that is correct heat range for a .045 gap may be too cold if gapped at .065!!! Link to comment Share on other sites More sharing options...
j.j.&s.racing Posted February 26, 2014 Author Report Share Posted February 26, 2014 are you talking about wider than stock hei gap of 45 or starting smaller and getting to 45.thanks for all your help and you too jumster Link to comment Share on other sites More sharing options...
Truck99 Posted February 26, 2014 Report Share Posted February 26, 2014 We run the NGK UR-5 in our sportmod motor with EQ heads. They seem to work very well. Typical HEI gap. Link to comment Share on other sites More sharing options...
j.j.&s.racing Posted February 27, 2014 Author Report Share Posted February 27, 2014 thanks chase Link to comment Share on other sites More sharing options...
JLWelding Posted March 8, 2014 Report Share Posted March 8, 2014 Got a question on spark plugs. First a little history on me, I quit racing in the early 80's. I raced mainly motor cycles and a few older Pontiacs with point systems. Built everything I raced. My son got me interested when he started racing sport mod. Ok lets use AC Delco for example. 350 chevy recommends AC R45, I see a lot of people running colder plugs rather than step up to bigger jets. To me your defeating the purpose, go up on your jets till you have the coffee color tan with the heat range for the R45. For example your older Harleys with chrome straight pipes would always turn blue because you released the back pressure and result it ran leaner. We left the same plugs and increased the jet size till it had the brown tint to the plug. I see guys put in plugs and freak its to hot and go colder on the plugs and forget about jetting. Was I doing it wrong for 15 years? Link to comment Share on other sites More sharing options...
jwmbishop Posted March 10, 2014 Report Share Posted March 10, 2014 Not really - it IS a balance - and you were getting to the point of most fuel with complete burn. However you were tuning to the plug. Not tuning to the engine by using the plug. The stoiciometric edge is fairly wide from perfect to too rich, and dangerously narrow from perfect to too lean. So old school was to run safe - not lean enough to risk damage (but at cost of lower burn temp) with enough fuel to quench any sudden lean spots due to distribution - hence seeing color on the plugs. (and unleaded does not give good color!!!!!!!). Using electronics has shown how to get right to the edge! You have to make sure heat range is correct before you can rely on the plugs visuals. And you were using the color of the plug insulator. Thats not the best way - use the strap to determine heat range (when I open the header cutouts on my SBC I notice the plug is then showing cold - with less back pressure - or more presicely lower reversionary flow - more heat leaves with the flow). The heat range is simply the range at which the plug becomes "self cleaning" - add oil from ring wear over the season for example - the plug that worked great at the start of the season is not getting hot enough to clean off the extra oil's hydrocarbons - and would appear cinnamon - when it used to be bright white. Then use the base ring to determine jetting. It should "blacken" one full thread turn. Less is tto lean - more is too rich. The insulator (nose) is only where you look for detonation (or distribution of fuel charge - off sided coloring) - I have seen a TON of bright white nose with heavier than necessary soot in the base ring and header...! I started using an AFR set like this - http://www.innovatemotorsports.com/products/lm2.php (basic kit - extra bungs and bung plugs can be had from Summit) - and only look at the plugs for heat range. FAR superior. You can even chart the changes needed for temp and humidity simply by tuning it during the day, then late evening etc and indexing the resultant jet size needed for each climate. Good targets are 15.1 idle, 14.1 low load (power valve closed) cruise, and 12.5 WOT - the higher the engine load the lower the first number needed. Then look at the plugs for info - and change jets as you normally would charting the AFR change the jets made. Same for pump shot/duration, powervalve and throttle blade idle stop. Tuning by ear, sight or nose has gone the wayside with the electronics being so much more accurate! Link to comment Share on other sites More sharing options...
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