Spark plug gap '84 Olds

[Mickey McChesney]

Changing the plugs on my '84 Delta 88. Shop manual and emissions label call for R46SX plug with a gap of .080. The plugs I removed were R46SZ with a gap of .060. .

 

Research says the 46SX plug is discontinued. Should I gap the new 46SZ plugs at the spec of .080?

[rocketraider]

Gap them at .060. The .080 spec was an early HEI spec that proved problematic as miles racked up. Lot of guys gap them at .045 with no problems.

[NTX5467]

As I understand it, from an ignition book I bought in the 1980s, the original HEI was supposed to have enough power to accommodate a .1000" spark plug gap.  Only thing was that with gaps greater than about .080" spark plug wire condition would be evident as miles grew and normal "wear and tear" accumulated.  As most emissions warranties were for 50K miles (100K miles in California), by the time the plug wires would deteriorate, the car would be out of the OEM warranty.

 

The more power a coil has to build to fire a plug makes it work harder.  There are also some issues with the carbon plug that transfers electricity from the coil's bottom to the distributor's rotor center contact.  That item will deteriorate, with age, sometimes, and will spark from the bottom of the coil directly to the rotor contact!  Many times, we'd see such things when a "no start" would result in the vehicle being towed into the shop at the first really cold snap of the year.  That's some power coil!  OEM, too.  Or it would burn through the distributor contact, through the distributor rotor itself, and "ground" through the distributor shaft, rather than through the spark plug..

 

The OTHER side of things was that during the fuel embargoes and slower sales for larger cars, many dealers would move the cars on the lots periodically.  The emissions-controlled cars would generally not ever get warm enough to get to base idle.  That meant that the automatic chokes were "on" when the cars were moved, which could also mean richer mixtures AND the spark plug's wider gap would be more easily fowled and mis-fired would result . . . on a new, "zero" miles car that you wanted somebody to BUY.

 

The wider-gap plugs were designed that for that wider gap, so that's the reason for the different letter designation after the heat range number.  The later "SZ" plugs were similarly designed for the smaller '060" gap. 

 

Other GM engines used a .045" gap with the HEI ignitions.  Somewhere, in the .045" and .060" gap range, there is supposed to be a gap which gives the optimum spark for better fuel combustion, IF the ignition system will support such larger gaps.  Therefore, these .060"+ gaps were more emissions-oriented than anything else, to me.

 

On a side note, it always seemed to me that Olds V-8s were generally more fuel efficient (at least in the middle 1960s and newer) than some other GM brands' engines, in general.  Yet for those same engine family members to meet federal emissions, they had some of the most fringe-oriented tactics to get them past emissions of any GM brand engine.  The multitude of strangling emissions hardware and then the wider spark plug gaps later on.  With, relatedly, a disarming decrease in engine power compared to similar engines in other GM brands!  All of this with the "after-treatment" catalytic converters!  The horsepower numbers might have been similar, but their performance level was gutted from former levels.   It just seemed to me that something was amiss! 

 

Yet, if "re-tuned", they really worked as great as they were designed to be, initially.  I knew of one such '72 Cutlass 350 that ran better than the proverbial "bat" and got 22+mpg on the highway.  Back when most cars were doing good to get 18mpg!

 

NTX5467