The best 1966 427 sparkplug
Does anyone have any experience or feedback by using an AC Delco,4 Rapid Fire Performance Platinum sparkplug? I am looking for the best plug for my 427. Dutch
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Re: The best 1966 427 sparkplug
I don't know about #4 Rapid Fires but some here have recommended the 45 vs. the original 43 heat range plug
so I suppose if you could cross reference the Rapid Fires to the 45 heat range regular AC plug it should be fine.
You might try the ACDelco website.
Richard -
Re: The best 1966 427 sparkplug
Dutch,
This thread has some recommendations from Duke:
I assume (Terry's favorite word) that you're interested in performance, not judging.
JoeComment
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Re: The best 1966 427 sparkplug
AC R45XLS work great for street driving.Comment
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Re: The best 1966 427 sparkplug
Anything more than a "two-dollar" plug in a vintage Corvette is a waste of money. You can cross the AC plug that Clem recommended to any other manufacturer on their web site. The important thing is to get the proper geometry and heat range, and AC heat range "5" or equivalent in another brand is best for all road driving for all vintage engines.
Most modern replacement plugs are resistor type, which did not become OE until 1969, so I prefer non-resistor types in earlier engines. Resistor plugs are typically indicated by an "R" in the designator, and some manufacturers offer specific plug geometry/heat range in both resistor and non resistor versions.
The non-resistor plugs I recomended in the thread that Joe referenced are for small blocks, but equivalents to the AC R45XLS or equivalent non-resistor 45XLS for vintage big blocks are a Google search away.
Basic spark plug design has not changed for about 100 years, but reliability has improved with modern manufacturing techniques, and material improvements have increased longevity. Platinum electodes last longer, but carry a considerable price premium, and you have to ask: Do I need a 100,000 mile plug in my vintage engine that may see a few hundred to a few thousand miles a year?
The bottom line is: There is no "best plug". Any proper heat range common copper core, nickel electrode two-dollar plug will provide 15-30K miles of service if your igntiion system is operating properly and the fuel system provides a proper mixture for all operating conditions - idle, cruise, and WOT.
The plug fouling that many of us experienced back in the day was caused by too cold OE plugs and leaded gasoline. Once we figured out that hotter plugs were better for normal road driving, the fouling issues typically went away, even with leaded fuel. Unleaded gasoline results in considerably less deposit buildup, which effectively doubled the life of common two-dollar spark plugs.
DukeLast edited by Duke W.; January 8, 2013, 10:43 AM.Comment
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Re: The best 1966 427 sparkplug
By having PerTronix Ignitor II and the big flame thrower coil,and 8.5MM MSD WIRES have any different effect to the sparkplugs LIKE MAKING THEM BURN DIFFERENTLY? Also My engine was rebuilt with more gusto, THAT I did not do. Will the NGK B4 sparkplugs be the best choice no matter if it is a high powered car or not? DutchComment
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Re: The best 1966 427 sparkplug
No and No. You better reread all the responses - CAREFULLY!!!
Spark plugs don't "burn". They merely initiate the combustion process. The B4 is for small blocks.
DukeComment
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Re: The best 1966 427 sparkplug
Dutch
I've run NGK BR6ES gapped at .035 in '65 L78 on the street for several year now and feel they are better than Champion or AC - used to run the R45XLS which will serve you well, I just believe that the NGKs look a lot better after 5 to 10K than any other I have tried.Comment
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Re: The best 1966 427 sparkplug
NGK heat range 6 is approximately equivalent to AC 4, so these plugs are colder than AC 5, but should be okay, especially with TI. (The first digit in the AC number means 14 mm thread)
The NGK equivalent to the non-resistor 45XLS is BP5ES. These are projected tip plugs as indicated by the S in the AC number and P in the NGK number. The non-projected tip equivalents are 45XL/B5ES. The basic geometric features of these plugs are 14 mm thread, 3/4" reach, 13/16" hex, gasketed seat.
I believe the original big block plugs (43N?) were non-projected tip. The direct NGK cross to the 43N is B7ES. In the NGK heat range system, the larger the number the colder the plug. This is opposite most other manufacturers where a larger number is a hotter plug.
NGK and Denso plugs have a more corrosion resistant coating than AC plugs, which is one reason I prefer them. They also offer non-resistor plugs in proper geometry and heat range for most vintage Corvette engines.
DukeLast edited by Duke W.; January 9, 2013, 11:43 AM.Comment
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Re: The best 1966 427 sparkplug
These are my ACDelco R43XLS after 3 years. Any diagnosis is welcome. What is the difference between projected and non-projected plugs? thanks, DutchComment
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