8/19/2023 0 Comments Ngk heat range chart![]() Fuel octane is a main one, just as combustion chamber design is also in the mix, as David Vizard proved, without any electronic detonation limiter mechanisms. I don't know if I've seen any data on how E10 might affect spark plug heat range per se, just that stoich is more like 14.2 rather than 14.7 (due to the lower heat content of E10 fuel blends).īy observation there are several things which can affect engine "ping/clatter". Even with a non-CAP carb and 12.5 degrees initial in the '66 383 2bbl, it was possible to adjust to a 14.2 afr, but the idle was more shaky, so we went back to the "lean best idle" settings. And, with a Sunn air/fuel meter hooked to the engine's exhaust system, once the engines free-running rpm got into the 2500rpm range (criuse no-load rpm), the meter's needle would head toward 14.7 "stoich" on the meter. Just as they might play with fuel curve calibrations and the distributor's spark advance rate/total timing.Īlso note that this was back in the days of fully-leaded fuels to increase Research Octane ratings, rather than rely upon "aromatics" to do similar things. On the other hand, a normal "enthusiast" might tinker with their engines a bit more and be more inclined to go a bit colder with their normal plugs, if they drag raced, if necessary. With something one notch colder if needed, from the normal J-10Y or J-11Y spec. So the colder plugs on engines which might get into those situations (i.e., the 4bbl motors). Just cruising around, no need for premium gas, only during "chase" periods. One thing that was mentioned in prior times, was that the 4bbl HP motors usually had lower total timing settings and colder plugs so that the law enforcement operatives could use regular-grade fuel (From their normal "fleet" fuel supply) and it not compromise their WOT extended-use performance. It did NOT like regular fuel of any brand, period, at factory specs. From new, it preferred premium fuel, which we fed it all the time, so it was happy. On our '66 Newport 383 2bbl (40degrees total advance), the J-14Ys worked just fine. No clatter with premium fuel (the spec) at WOT. Oil consumption was about 1qt/2500miles at 80K miles, fwiw. My observations on the '70 Monaco 383N was that the J-11Y worked just fine in normal driving. In all cases, the distributors usually had about 25 degrees (crank degrees) timing in them, when combined with the initial timing usually putting them in the 34-38 degrees total area. Our '72 Newport 400 2bbl 8.2cr spec'd J-13Y plugs. The 1965 Chrysler FSM indicates that the 383 2bbl (9.2cr) and other non-"Power Pack" 383 and 413 10.0cr) engines used J-14Y and the 413 Power Pack used J-10Y. In the '70 Dodge Polara/Monaco FSM: 383 2bbl 9.2cr J-14Y 383 4bbl 9.5cr J-11YĤ40/350 9.7cr J-13Y 440/370 9.7cr Spec Cam J-11Y These uses had been typical for many years, at this time. Which was typical for Chrysler B/RB engines for ages. In the 1966 Chrysler service manual, 9.2cr 383 2bbls were spec'd for Champion J-14Y plugs, with the 383-4bbls in the J-10Y range. So a slightly richer WOT power mixture might be in order? If your 93 octane fuel has 10% ethanol, you might need to go a bit richer on the calibration at WOT as 0 ethanol content has a stoich ratio of 14.8 which can go down to about 14.2 stoich (optimum afr) at cruise with 10% ethanol. Seems like the old B/RB 10.0cr 4bbl engines went as cold as a Champion J-10Y? If I remember my NGK crossovers, you're not quite that cold with what you now have? Sometimes, a colder plug will not contribute to a clatter/ping tendency as a hoter plug might. How are the plugs coloring after your "pulls"? Any variations in the ceramic insulator color between the cylinders? None show signs of leanness or richness, for example? 5 degree BTDC decrease in total timing? Usually, it takes more than just. But you got rid of the slight ping at 5Krpm with just a. NGK Iridiums?ġ2.7 afr sounds about right to me, fwiw. Remember that NGK heat range numbers are higher for the colder plugs, unlike other brands whose heat range numbers increase with the "hotness" of the plug.
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