Guys I bought a used blown 400 chevy..I have just had the carbs rebuilt and now putting in new spark plugs.. I have to run the accel shorty plugs because or clearance issues.. The ignition system is all msd dist and coil and also the al6 box.. What would be a good plug gap ?? Thank you for any help.
With the MSD the higer the comp ratio the tighter the gap. I would start at .045. If the intended use is drag strip only you can close the gap. peace
Get rid of the accel plug. What they call a 'shorty' plug is a normal race plug and availble from ngk or autolite... accel is just telling you a lie. I generally set the gap at .035, when you get a proper set of plugs the ground strap will be shorter than you are probably used to and i lay the feeler gage sideways across it instead on going straight in. You can open gap further but with the short electrode you'll get an odd angle and the spark can deflect. The heat range for street driving will be very important, if you tell us what head if aluminum/cast iron we can give more help. Throw that accel bullshit in your neighbors trash can, they ain't even good enough for your trash can.
i have cast iron angle plus heads .. i have to run the short plug because of clearance issues on the front two cylinders ..
Get yourself some ngk R-5673-8, that would be a good one to start with. If the motor is running hot you might try a -9 plug but i'd be cautious because a -9 might be too cold a plug for proper idle. It'll be an experiment thing. Gap it at .035. It is the same length as the accel 'shorty', it is higher quality and about $15 for a set of 8. Autolite Racing would be an AR133 or AR134, they have a high quality nickle-like material - the street plug would be a 133 or 134 they are blck oxide finish and may not be 'shorty'. The 'AR' series are race plugs and short, they'll also cost about $30 a set. I prefer the NGK. I hope i helped, oj
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