Correct plug gap
Thread Starter
Racer
Joined: Oct 2006
Posts: 412
Likes: 1
From: St. John's Newfoundland
Correct plug gap
Hey Guys
Just a quick question. I've just build a 383, Edlerbrock 200cc heads 10:1 compression and a Comp Cam 274H camshaft. I am using the MSD 6AL box and my dist. has no vacuum advance. What should my plug gap be. MSD recommends .050 to .060 for 10:1 and below. The plug is Champion RC12YC. Does this sound right to you guys.
As always, any and all advice is appreciated.
Just a quick question. I've just build a 383, Edlerbrock 200cc heads 10:1 compression and a Comp Cam 274H camshaft. I am using the MSD 6AL box and my dist. has no vacuum advance. What should my plug gap be. MSD recommends .050 to .060 for 10:1 and below. The plug is Champion RC12YC. Does this sound right to you guys.
As always, any and all advice is appreciated.
Race Director
Joined: Sep 2002
Posts: 10,362
Likes: 4
From: San Diego - Deep Within The State of CONFUSION!
Hey Guys
Just a quick question. I've just build a 383, Edlerbrock 200cc heads 10:1 compression and a Comp Cam 274H camshaft. I am using the MSD 6AL box and my dist. has no vacuum advance. What should my plug gap be. MSD recommends .050 to .060 for 10:1 and below. The plug is Champion RC12YC. Does this sound right to you guys.
As always, any and all advice is appreciated.
Just a quick question. I've just build a 383, Edlerbrock 200cc heads 10:1 compression and a Comp Cam 274H camshaft. I am using the MSD 6AL box and my dist. has no vacuum advance. What should my plug gap be. MSD recommends .050 to .060 for 10:1 and below. The plug is Champion RC12YC. Does this sound right to you guys.
As always, any and all advice is appreciated.
Burning Brakes
Joined: Aug 2005
Posts: 1,164
Likes: 1
From: Europe, France
A larger spark plug gap will stress your ignition components much more.
I have tried everything between 0.040 and 0.065 and found that there was no power gain above 0.045.
I've got a MSD-6AL ignition box, Mallory 55000V coil, ACCEL Shorty plugs and MOROSO Blue Max Spiral Core 11mm diameter wires.
Cylinder heads are stock. Compression ratio is 9:1.
I have tried everything between 0.040 and 0.065 and found that there was no power gain above 0.045.
I've got a MSD-6AL ignition box, Mallory 55000V coil, ACCEL Shorty plugs and MOROSO Blue Max Spiral Core 11mm diameter wires.
Cylinder heads are stock. Compression ratio is 9:1.
Melting Slicks
Joined: Oct 2002
Posts: 2,314
Likes: 111
From: St Louis MO
Hey Guys
Just a quick question. I've just build a 383, Edlerbrock 200cc heads 10:1 compression and a Comp Cam 274H camshaft. I am using the MSD 6AL box and my dist. has no vacuum advance. What should my plug gap be. MSD recommends .050 to .060 for 10:1 and below. The plug is Champion RC12YC. Does this sound right to you guys.
As always, any and all advice is appreciated.
Just a quick question. I've just build a 383, Edlerbrock 200cc heads 10:1 compression and a Comp Cam 274H camshaft. I am using the MSD 6AL box and my dist. has no vacuum advance. What should my plug gap be. MSD recommends .050 to .060 for 10:1 and below. The plug is Champion RC12YC. Does this sound right to you guys.
As always, any and all advice is appreciated.
With a smaller plug gap, I have found that the economy was not as good - a smaller spark does not hit as many molecules of fuel, especially under high vacuum conditions, so a larger gap with a longer spark really does help - and this ignition box has enough kick to jump the larger gaps. Just make sure the rest of your system is in good condition and you'll be fine!
__________________
1978 Corvette
406 SBC AFR heads Lunati roller Quadrajet TH-350 3.08
11.59 sec / 118.9 mph 1/4 mile
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
With an MSD box and other suitable ignition components, .050-.060" plug gap would be best, IMO. Take advantage of the higher spark energy that the system will produce which allows you to go to a wider gap/bigger spark.
Instructor
Joined: Dec 2009
Posts: 109
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From: Nassau co. NY
If you go to the MSD Paperwork, it states recommended gap based on compression range. Take advantage of the hotter spark and run larger at .050". I do in my 10.6:1 motor and i runs increadible with absolutely no adverse effects. Go to MSD and check out the instruction papers of the 6A/6AL.
Greg.
Greg.
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Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
those wide gaps are all right or OK for computer controlled 'emissions environmental 'tree hugger engines, not for high performance.....but i suppose there Ok for the wifes Olds or whatever
Le Mans Master
Joined: Dec 2003
Posts: 5,727
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From: Fremont CA
Run big electrode gaps over 0.050 and you'll start frying your plug wires/distributor rotor/distributor cap. The high voltages required to jump a 0.050-0.060 plug gap will try to find any place to leak and ground before they try to jump across a big plug gap in a high pressure cylinder bore.
0.045" is about as wide as I would run a plug gap and expect my secondary ignition components to live a reasonable life.
0.045" is about as wide as I would run a plug gap and expect my secondary ignition components to live a reasonable life.
Burning Brakes
Joined: Aug 2005
Posts: 1,164
Likes: 1
From: Europe, France
Run big electrode gaps over 0.050 and you'll start frying your plug wires/distributor rotor/distributor cap. The high voltages required to jump a 0.050-0.060 plug gap will try to find any place to leak and ground before they try to jump across a big plug gap in a high pressure cylinder bore.
0.045" is about as wide as I would run a plug gap and expect my secondary ignition components to live a reasonable life.
0.045" is about as wide as I would run a plug gap and expect my secondary ignition components to live a reasonable life.
That's what I was talking about in post #3
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Gosh!! I wonder how all the cars built in the last 20 years get by with those larger plug gaps without "frying their plug wires"??? 
[Perhaps they buy plug wires made for HEI systems...hmmmm]
[Perhaps they buy plug wires made for HEI systems...hmmmm]
Race Director
Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
Nope, there trying to comply with emission standards and went all the way to .080 before they backed off...that's where smog engines run. Performance engines run best at .035...But do whatever you want, its your piece and not everyone has a high performance engine.
Race Director
Joined: Sep 1999
Posts: 11,358
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From: Plano TX
The RC12YC plug is meant to be gapped at 0.035". If you want to run a wider gap (don't know why you would) you need a RC12YC5 plug.
BTW, for those who think wide gap = more power: My '05 BMW M3 came from the factory with 0.028" gaps...
I run my 454 at 0.035. I tried a wide gap (0.050), but got a mirsfire where the spark went down the center electrode and jumped to the shell instead of the ground electrode.
BTW, for those who think wide gap = more power: My '05 BMW M3 came from the factory with 0.028" gaps...
I run my 454 at 0.035. I tried a wide gap (0.050), but got a mirsfire where the spark went down the center electrode and jumped to the shell instead of the ground electrode.
Melting Slicks
Joined: Oct 2002
Posts: 2,314
Likes: 111
From: St Louis MO
__________________
1978 Corvette
406 SBC AFR heads Lunati roller Quadrajet TH-350 3.08
11.59 sec / 118.9 mph 1/4 mile
Thread Starter
Racer
Joined: Oct 2006
Posts: 412
Likes: 1
From: St. John's Newfoundland
Well, Larrywalk, 7T1vette, 69VetteAngle, agree with the larger gap.
zwede, Ironcross, SolidLT1,73StreetRace, & SanDiegoPaul, for the smaller gap.
I kinda thought the .050 - .060 was a little big, and with 5 members going with the smaller gap and 3 going with the larger gap, it just makes me more courious why MSD recomends the larger gap....
Clyde
zwede, Ironcross, SolidLT1,73StreetRace, & SanDiegoPaul, for the smaller gap.
I kinda thought the .050 - .060 was a little big, and with 5 members going with the smaller gap and 3 going with the larger gap, it just makes me more courious why MSD recomends the larger gap....
Clyde
Race Director
Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
Ive done a little racing myself and both Champion and Autolite representatives told me to run .035. And why doubt the engineers that make them. I know I dont make them, I just use them.
Race Director
Joined: Apr 2000
Posts: 17,641
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Try them all, I did, 35 to 50 settled on 40. The really weird thing is I think the .050" gap was making my exhaust stink real bad. When I went back to .040" it is much much better, still stinks a bit but doesn't stink up the whole neighborhood anymore.
Don't know if the smell has anything to do with the gaps or not but would be interesting to find someone else who had a similar experience.
I also found the idle sound a little louder and not quite as smooth with the wider gaps, would be interesting to do some chassis dyno runs to find out if you make any more power at different plug gaps
Don't know if the smell has anything to do with the gaps or not but would be interesting to find someone else who had a similar experience.
I also found the idle sound a little louder and not quite as smooth with the wider gaps, would be interesting to do some chassis dyno runs to find out if you make any more power at different plug gaps
Thread Starter
Racer
Joined: Oct 2006
Posts: 412
Likes: 1
From: St. John's Newfoundland
Try them all, I did, 35 to 50 settled on 40. The really weird thing is I think the .050" gap was making my exhaust stink real bad. When I went back to .040" it is much much better, still stinks a bit but doesn't stink up the whole neighborhood anymore.
Don't know if the smell has anything to do with the gaps or not but would be interesting to find someone else who had a similar experience.
I also found the idle sound a little louder and not quite as smooth with the wider gaps, would be interesting to do some chassis dyno runs to find out if you make any more power at different plug gaps
Don't know if the smell has anything to do with the gaps or not but would be interesting to find someone else who had a similar experience.
I also found the idle sound a little louder and not quite as smooth with the wider gaps, would be interesting to do some chassis dyno runs to find out if you make any more power at different plug gaps
It's very easy to take advise from members who have to #'s.