Can anyone tell me is there is a marked difference between a R43 and R45 plug? I know the R45 is a hotter plug, but for normal driving conditions in my '60 fuelie would one be better than the other?
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Re: spark plugs
Dave:
I believe that the owners' manual calls for AC43 plugs for extended high speed/heavy duty use........................AC44 plugs for all around use.......................AC45 plugs for city driving/long periods idling.
Many folks here recommend AC45 plugs. I have been using AC44's in my 327/365 (L76)with no fouling problems.
Since non resistor plugs are not READILY available, and R44's are no longer made, then the choice is R45. The R43's are too cold, and will be prone to fouling under normal driving conditions. -
Re: spark plugs
Dave,
I would consider an AC 46 or R46 plug for your fuel car. 43 heat range is cold for a carb. car so its far to cold for and FI car. Your original owners Manual calls for AC 46 for city driving and AC 44 for town and country driving but does not differientate between engines. FI motors tend to run rich thus the need for the hotter plug. My $.02.Comment
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Re: spark plugs
You'll foul the 43s in no time in street driving. Even the OE 44s are too cold.
For normal street and highway driving AC heat range "5" works best in all SBs, regardless of horsepower rating. It's driving conditions that determine plug heat range, not engine horsepower.
I used 43s for race track hot lapping back in the sixties, and they were just right for that driving condition.
Once I started using 45s on the street my fouling problems went away.
DukeComment
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Re: spark plugs
Duke,
Are you recommending AC 45S plugs or 45's in general, such as AC45?
RickComment
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Re: spark plugs
Traditionally I used AC 45s, but they are not longer available. The AC R45 (resistor type) is the closest AC substitute. A R45S has an extended tip, which is okay, but may interfere with the domes on SHP engines if the quench clearance is at minimum or below.
DukeComment
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