Spark Plug Gap

C

Charles Brock

Senior Member
I'm getting ready to install a new set of Champion H-10 plugs into a 8ba, 276 cu. in. street motor with Offy 425 heads, dual 97's, Winfield SU-1A cam and Mallory 12V electronic ignition.
I have read spark plug gap specifications anywhere from .024 to .050!
What should the spark plug gap be with electronic ignition?
Thanks
 
I would stay around .025 to .035 at the most. Too high a gap can build excess voltage which can result in crossfire in the wires and cap.
 
i run mine 32-35. be carefull with those champions.. ive had the grnd electrode fall right off when adjusting those. quality parts there...
 
Be sure an put a dab of antiseize compound on the threads to prevent galling of the aluminum. I have been told that Champions have cut threads and NGK are rolled, which is better.
 
You don't have the original engine anymore. (276 CI) I would go with a .032 gap and use Autolite 216 or Ngk plugs. Champions are not what they used to be unless you can get some originals.
 
I run .025 gap in my 276 engine. I've got a crab distributor and a larger gap leads to early cap failure. I don't think the 8BA caps are as sensitive. But .025 works great.
 
electronic ignitions usually run coils in the 50,000v range, so the can run a wider gap for better ignition, .045 to .048 is standard
 
Plug gap should stay with the engine combustion chamber etc , NOT the ignition. Wider gap loads the system even more . .025 works very well with all ignitions in a flathead.
Wider gaps were designed for emissions and lean air ful mixtures as well as longer burn times . Highly unlikely your engine needs either one.....
 
Bubba hit the nail on the head, wider gaps need more voltage to cross. With a hot coil this can cause arcing in the dist cap. I don't like Champion SP because they have a cut thread. Try NGK BL6. New heads from Offy and Edelebrock now have a 3/4 thread length. This allows for higher lift cams, or recessing the plug bore a power-tip plug. Not sure if this would help a low compression engine, however it should help burn a leaner mixture. Try everything that's how you learn.
 
The last Autolite 216s I bought were made in China and were of very poor quality (crooked center electrodes with twisted grounds in 5 out of 8 plugs), and I've never liked Champion. My choice now is NGK B4L or B6L for a 7/16" reach flathead plug.
 
if you guys will go back and read his post he said he was installing a mallory ign dist not a stock dist, so all the stock specs dont apply, the mallory ign is designed for the higer voltage and larger gap, the longer and hotter the spark the better the combustion in the cylinder
 
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Seems to me, ALL the variables assocoiated with ignition have been changed from stock. His ignition system has the capacity to run a wider plug gap without compromising reliabilty and consistency of firing. I wouldn't be afraid of .035 for a min. gap.
 
On Mallory Magnetic Distributor systems. Quote;SPARK PLUG GAPS For street applications, use your engine manufactors specifications. For racing applications, start with the manufactors specifications, then experiment with and closely monitor various gaps to achieve maximum performance. I think that says it all.
 
I tried wider gaps like .035 and had trouble with tracking in the caps on my mallory ignt. 12 volt. Now i'm at .025 ,and it's worked ok for several years.
 
ive had tracking with those red mallory caps also. quality just aint what it usta be. no more trouble when i put an old ford bakelite cap on...
Mick/mo said:
I tried wider gaps like .035 and had trouble with tracking in the caps on my mallory ignt. 12 volt. Now i'm at .025 ,and it's worked ok for several years.
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