Mild 318 pinging

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I agree. Worth experimenting with and 16 seems very hot. Hotter than I recall ever using in a factory 318.
Factory 340 in '68 was 9 although many of the box parts stores try to say otherwise, its right in the factory manuals.
later 340s may have gone as hot as 12.
 
The correct heat range for Mopar V8s is a 5 in NGKs. You would only go hotter to a 4 if the engine was badly worn, burning oil & fouling plugs.
There is rarely any need to go to colder plugs; only if using a power adder or at WOT for sustained periods.
 
Just so I'm sure I understand. Are we saying that if I drop to a colder plug, I may be able to bump the initial timing back up without ping? I never gave any thought to plug heat range other than just purchasing plugs for a 340. That's what I get for assuming that what was listed for sale would be correct. Always something new to learn.
 
1973dust said:
Just so I'm sure I understand. Are we saying that if I drop to a colder plug, I may be able to bump the initial timing back up without ping? I never gave any thought to plug heat range other than just purchasing plugs for a 340. That's what I get for assuming that what was listed for sale would be correct. Always something new to learn.
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Yes
 
Bewy said:
The correct heat range for Mopar V8s is a 5 in NGKs. You would only go hotter to a 4 if the engine was badly worn, burning oil & fouling plugs.
There is rarely any need to go to colder plugs; only if using a power adder or at WOT for sustained periods.
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That would be correct on a stock engine.
 
1973dust said:
Just so I'm sure I understand. Are we saying that if I drop to a colder plug, I may be able to bump the initial timing back up without ping? I never gave any thought to plug heat range other than just purchasing plugs for a 340. That's what I get for assuming that what was listed for sale would be correct. Always something new to learn.
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I think its borderline now. I'd put miles on on it and a full work out, then as a seperate step experiment with a timing change.
To get the most out of the widest range of rpm and conditions the current timing curve (shape) needs a little tweaking regardless of the plug.
 
Frank,
This IS a stock engine in terms of spark plug requirements. You want the HOTTEST spark plug the engine will tolerate without causing pre-ign. NOT the coldest like some people think. Colder plugs cause misfires which apart from the hp & economy losses, puts more load on the engine, which in turn can cause pinging. Pinging is load related. Anyone ever hear of an engine pinging at idle?
 
Bewy said:
Frank,
This IS a stock engine in terms of spark plug requirements. You want the HOTTEST spark plug the engine will tolerate without causing pre-ign. NOT the coldest like some people think. Colder plugs cause misfires which apart from the hp & economy losses, puts more load on the engine, which in turn can cause pinging. Pinging is load related. Anyone ever hear of an engine pinging at idle?
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You want a plug hot enough to keep itself clean. To cold and it will foul. Too hot and it will ping. Idle has nothing to do with it.

https://www.autolite.com/docs/defau...ing-spark-plugs/autolite_heat-range-facts.pdf
 
Idle has EVERYTHING to do with it. There are less power strokes at idle, so the plugs 'cool off' & fail to burn off deposits, & then misfire.
 
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