Going to be doing a tune up soon and want to know what my best options for spark plugs are? Did a search and only found a couple threads but werent talking about a 350 Rocket. Is my best bet still trying to find NOS green ring AC Delco R46S plugs on ebay? I found a set for $30 on there.

Going to be changing over to Pertronix Ignitor w/ Mallory Cap and rotor if that makes a difference?

I have the option of getting a set of 8 of the following for around $5 because of a good rebate offer right now. What are you opinions on these?

AUTOLITE 86 AP86 Single Platinum
CHAMPION 58 RJ18YC Copper Plus
AC Delco R45S (New Style)

 

Any of those three will work fine, though I'd be a little partial to the Autolites in this case. All these plugs are about one heat range colder than the OE R46S but you won't notice any difference in daily use especially with current fuels. The hotter plugs were designed to keep carbon and lead deposits burned off back in the day.

With a Pertronix, if you use their coil, you will want to open up the plug gap to about .040 or so from the OE .035 gap spec for optimal performance, but .035 will work fine too.

 

I've been using the Champion RJ18YC or something like that, they work pretty well so far. Nice and clean so far with my couple weeks of testing.

 

Looking up at a few older spec sites most recommend C44S plugs for a 350 in a 68 Cutlass. When looking at Fusick or places like RockAuto, they recommend the newer AC Delco R45S. The OE gap recommend is .30. This is confusing me.

I am going to be changing the coil out to a Mallory 50k coil. I found a NOS set of AC R45S plugs for $15. They have 4 green rings on them. Would that be a good match?

 

A set of NOS AC plugs for $15 is a good deal.

C44S sounds like an industrial engine plug.

All the R stands for is Resistor to cut down on radio interference. Before about 1968, most GM plugs were simply numbered, i.e. 43, 45, 46 which is the heat range; the lower the number the "colder" the plug and vice-versa. Sometimes they had a suffix- S meant extended tip, FF or FFS was for aluminum and aircooled engines. Later you got into T, SX, TSX/STX and all those suffixes to contend with emissions-spec engines.

.030 was a good compromise spec for stock ignition coils driving points ignition systems. With that Pertronix and hot Mallory coil, you can easily go .040 on your plug gap. What that does with a high-output coil is make a big fat arc across the plug electrodes, hence a stronger ignition.

You may find that with the Pertronix, you will have to fiddle with your base timing since odds are it will be way advanced after you install the Pertronix.

 

Regular old Autolites...hands down!

 

Thanks for all the info! I'm going to go ahead and order that NOS R45S set I found for $15 and see what happens.

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