View Full Version : SPARK PLUGS
09-03-2003, 08:59 AM
I HAVE A 78 Z28 WITH A 350, 4-SPD, 3:73 GEARS. THE ENGINE HAS 10.5:1 COMPRESSION, DART 215cc RUNNER, 64cc COMBUSTION CHAMBER HEADS, COMP CAMS EXTREME 268 CAM, ROLLER ROCKERS, DART RAISED GAP, DUAL PLANE INTAKE, HOLLEY 4160 750cfm, MSD BILLET DISTRIBUTOR, MSD 6AL BOX, BLASTER2 COIL, MSD PLUG WIRES, CERAMIC FULL LENGTH HEADERS, K&N 4" FILTER. CLOSE RATIO T-10 4SPD, AUBRN POSI W/ 3:73GEARS. THIS IS A FAIR WEATHER CAR THAT SEES THE DRAGSTRIP OFTEN.
OK, WHAT PLUG WOULD YOU RECOMEND WITH MY SETUP? I'M NOT SURE ON THE HEAT RANGE? I HAVE A BOSCH PLATINUM NOW BUT NOT SURE WHAT IT IS?
THANKS, DAN IN MISSISSIPPI
09-03-2003, 11:17 AM
Choosing the correct spark plug design and heat range is important when trying to get all the performance possible. Since there are so many engine combinations and manufacturers, MSD cannot recommend which plug or what size gap is exactly right for your car. It is recommended to follow the engine builder’s or manufacturer’s recommendations for plug heat range and gap. Once a proper plug is selected, you can experiment with the gap to get the best performance. By using these recommendations as a starting point, you can experiment by opening the gap in 0.005" increments then
test. When the performance falls off, the gap is too large. Carbureted or fuel injection engines can use larger gaps, but turbo or supercharged engines should stick with
the smaller gap. If no significant gains are achieved, go with the smaller gap. Remember, the larger gap taxes the plug, wires, cap and rotor. After changing the gap, reading the spark plugs is a helpful tool in getting the right tune up. The air/fuel ratio and how it’s burning can be read on the ceramic portion of the spark plug. A ring can be seen where
the effective heat transfer takes place. The closer this ring is to the tip, the richer
the mixture. Closer to the base of the plug means the engine is running more lean.
Rule of Thumb Plug Gap
UP TO 10.5:1 .040 - .045
10.5:1 - 13:1 .032 - .040
OVER 13:1 .025 - .032
Note: These are recommended for normally aspirated engines only. Reduce the gap for blower, turbo or nitrous applications.
11-10-2003, 12:09 AM
Just wanted to say THANK-YOU MSDTECH2 for the rule of thumb on the Gap for spark plugs....I was going to ask the same question...But due to your message board My question has been answered..And Thousands of THANKS TO ALL YOU TECH GUY'S @MSD IGNITION
11-10-2003, 03:01 PM
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