What is your preference in sparkplugs ? What about heat ranges at the track ? Can someone explain about this a little bit for those of us that don't know:confused: Richard:confused:
The stock heat range of your plugs allows them to trasfer heat slowly enough to clean the combustion products away from the electrodes so that they continue to be usable over a long period of time. Raising your compression or doing anything that increases combustion temperature will make them overheat so you need to put in a heat range that is "colder" or transfers the heat away faster to keep them from burning away. That is why when you are building an engine you use "colder" plugs than stock. PaulS
PaulS; how does electronic ignition, Pertronix Ignitor ll, effect the plug wear? I put a stock plug, Motorcraft 45, and increased the gap to .040. Seems to run a lot smoother, and has more power on the low end. Will the plugs die prematurely, or last a while?
When I bought my 205's, AFR recommended a Autolite plug that I am using. I cannot remember the #. But they took all my engine specs and then recommended a plug.
Earl, If you're running a stock motor the .040 gap is probably OK but if you are running higher compression you may think about going the other way - say down to .030 or less depending on your engine. The ignition changes won't significantly change plug requirements so it is not a consideration. If you are running a racing ignition that uses very high amp output then you will notice your plugs will wear faster due to the ion transfer from the high electrical energy that is being used. On my stock Fords I usually run .028 gap but at that gap they tend to skip at an idle but they run real well when you are getting on it to pass or accellerate onto the freeway. They also last longer (because the gap grows but not to the point where they need to be replaced for a longer time. Typically a larger gap will run smoother at low engine demands and miss under high demand while the smaller gap will run better at the high demands and miss occasionally at low demands. The ideal situation is to find where your engine will tollerate the gap the best over the range of loads that you place on your engine. PaulS
PaulS; Thank you. I had it out today, and it runs real well down low. I don't race the car at all, so I think it will like it just like it is. You are very knowledgeable and your help is appreciated. Take care,
Hello Earl, Just a little different slant on things for interest. I run a Kenne Bell blower on a stock 5L efi engine at nearly 8 lbs boost. The plugs are Autolite #23 and gapped at .055. The engine it totally smooth and runs up without miss. This is testament to how good the 5L efi stock ignition system is. True, as the gap is closed up the engine idles rougher. This is an old trick and demenstrated many times in various other type engines. In an aky flat head engine, I use surface fire plugs with a gap of well over .100 but the magneto ignition system has to have enough reserve to handle such large gaps and this makes a ton of extra low end torque.. In most standard ignition systems, if you add up both the gap at the rotor/cap and the plugs, it is well past .100. IMO some company is missing the marketing boat not making a more precision rotor and cap assembly that cuts down on the gap at that point. An interesting thing to do is take an old cap and drill a 5/8" hole at the base of #1 post. Then look at the situation with a timing light as the engine runs. You can see the gap and what the advance does. On a centrifigal advance system the rotor stays pretty much in alignment. On an EFI car, the rotor appears to move in relation to the post due to the strobe effect and is the reason why the rotor tip is so wide to handle the wide timing range those engines work over, at up to 45* at times. The wide rotor tip ensures there will be some part of the tip in close alignment with the post at all times. If you see a gross missalignment on a centrifigal dist. then there is high likleyhood of a miss occurring at some point. Take care.
Bluegrass; thanks so much for the lesson. I am going to drill a cap and see what you are talking about, and see if differing the gap on the plugs and advance adjustments makes an appreciable difference. I'm going to drive to 71gold's place tomorrow, and get a look at how it runs on the highway with the 45's at .040. Runs great at idle, but haven't got it up to speed yet. Thanks, and I'll let you know,
