What gap on plugs

[JoeM29]

i am running msd, and i want to change my plugs, i was wondering what i should gap my new plugs too,
thanks, joe

[creative1]

all a, b, rb, and hemis have the same spark plug gap... .035 inches

[ehostler]

If you are running a nice performance MSD or Jacobs coil, you could probably go between .04 - .045 on the gap.

[landyacht67]

this maybe a stupid question but what do you really gain from larger plug gaps? better burn? more power? just curious

[dwc43]

I am running .048 gap on the race cars but could go more since I run the msd 7al2 and high vibe coil. Just start making it wider and wider until it picks up a high speed miss then close the gap by .005 and that's how to find the max gap your engine likes

As for what the bigger gap does; IT gives more space for the fuel to flow through as a wider spark jumps the gap it starts a bigger fire called the flame front. It speeds up combustion a little and gives it the chance to have a more complete burn of all the air and fuel in the cylinder. That will create max cylinder pressure which can add to more torque and hp.

Also as a racer I index all my plugs. That simple means I fix them so when they are installed the open gap of the plug will face the incoming intake charge. So it stops some turbulence around the plug until it can ignite since it doesnot hit the metal ground strap first. It lets it go straight through to the gap.

[George G. Leverette]

Assume you are running 9.5-1 or less compression ratio, MSD recommends the gap be set between .050-.060. Higher compression ratios require less gap. Both of my MSD systems are currently running the .050 gap without problems.

[dwc43]

I'm running 10.7 to one for referance there by our track rules. So the .048 works good with the higher cylinder pressure. Glad you mentioned that George. I forgot too. As the cylinder pressure goes up most all engines will want the gap a little tighter to some degree.

[moparmotorman]

in stock type ignition applications, .035 would be the correct sparkplug gap[as previously mentioned]. i'm running MSD 6al in 340 , 10.0-1 comp., and plugs gapped to .050 as per MSD reccomendations, so far so good no miss , no fouling.

[JoeM29]

the sad thing is tha i have no idea the comp of my engine, i think i will try them at .050, lets see how it goes,
thanks, joe