Author Topic: spark plug gap inquiry  (Read 1687 times)

merrill

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spark plug gap inquiry
« on: July 11, 2020, 12:43:03 »
hello All,
after following the "spark plug discontinued thread"
https://www.sl113.org/forums/index.php?topic=31179.0

and then some additional reading using the search tool (link below)
https://www.sl113.org/forums/index.php?topic=30312.msg219498#msg219498

I decided to go double check my ignition wires to make sure i was setting up my spark plug gap correctly
for my 66 230sl.

the car has a bosch red coil,  1.8 ballast and turns out my plug wires are 1 ohm resistance not 5 ohm.

my inquiry is what is the proper gap to use for this set up when installing non resistor plugs (w7dc) with 1 ohm wires?

I suppose with my current set up i suppose i could use resistor plugs since i only have the 1 ohm wires...

thanks i advance
matt
Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

merrill

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Re: spark plug gap inquiry
« Reply #1 on: July 13, 2020, 13:35:11 »
i think i will give .35 a try.

after reading many threads and the various manuals is seems .35 would be ok


since i have a red coil , 1.8 ballast non transistorized ignition i have some leeway to increase the gap.

my haynes manual recommends the spark plug gap be set to the following.
for non resistor plugs .28 to .32
with resistor plugs .35 to .39

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

merrill

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Re: spark plug gap inquiry
« Reply #2 on: July 13, 2020, 14:52:08 »
interesting i found a spark plug chart in an old chilton manual. 

they reference champion spark plugs with a gap of .020"  (picture)
Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

merrill

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Re: spark plug gap inquiry
« Reply #3 on: July 14, 2020, 13:00:42 »
just for fun i sent this inquiry to Gernold at sl tech.

he said to use. 8 mm or .0314"
Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

wwheeler

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Re: spark plug gap inquiry
« Reply #4 on: July 14, 2020, 15:14:42 »
I have similar ignition equipment and that is close to what I have run for years. Mine is .031". Can't quite get the last .0004" though.  ;)
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Benz Dr.

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Re: spark plug gap inquiry
« Reply #5 on: July 14, 2020, 17:15:38 »
I run .032" or whatever the stock plug is set at. 

.020" is too close.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC