Stock Vs Modified Plug Gap
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Team Owner
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From: Riverside County Southern California
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Stock Vs Modified Plug Gap
There is another thread on this but I did not wanted to hijack it. Here it goes
The gap for LT1 & LT4 engines is .050 for stock engines.
This is my situation:
I have a 58mm TB, ported modified heads, modified cam and ported intake. All done by Elliot Portworks.
This are the specs for all
Valves:
duration - 223 intake 230 exhaust
lift - .565 intake .565 exhaust
Lobe Separation Angle (LSA) 112
The heads flow 285 cfm at .600 lift on intake and 193 cfm at .600 lift on exhaust.
I gapped the plugs at .050. Is this the reason I'm getting misfires (engine light code P0300)? If this is the wrong gap for my set-up, if .050 is wrong, which gap should I use?
The gap for LT1 & LT4 engines is .050 for stock engines.
This is my situation:
I have a 58mm TB, ported modified heads, modified cam and ported intake. All done by Elliot Portworks.
This are the specs for all
Valves:
duration - 223 intake 230 exhaust
lift - .565 intake .565 exhaust
Lobe Separation Angle (LSA) 112
The heads flow 285 cfm at .600 lift on intake and 193 cfm at .600 lift on exhaust.
I gapped the plugs at .050. Is this the reason I'm getting misfires (engine light code P0300)? If this is the wrong gap for my set-up, if .050 is wrong, which gap should I use?
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
The misfire is from the slight lope the cam has. The HOT Cam, which is small than your cam causes this as well.
You can either raise the threshold rpm at which the PCM looks for misfire, you can disable misfire, or sometimes raising the idle speed to ~900rpm will take care of it. Regardless of method, the PCM needs to be reflashed.
You can either raise the threshold rpm at which the PCM looks for misfire, you can disable misfire, or sometimes raising the idle speed to ~900rpm will take care of it. Regardless of method, the PCM needs to be reflashed.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
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From: Tampa Florida
Thread Starter
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
Thanks Gents 
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
engines operating at low speed/low load will typ experience fewer misses with 'wider' spark plug gaps (early daze of emissions controls had some gm engines at .060'' gap to meet idle quality)...high rpm/high load will see better power/ lower emissions with 'tighter' spark gaps.
fwiw... back/day we ran a rail drag car/hilborne injected 302 chevy with a vertex mag, vertex recommended plug gap was .020''... in 'the fog of battle', we ran a set of plugs 'out of the box' at .035'' and lost a tenth, next pass closed same plugs to .020 and got the tenth back.
u chuz
fwiw... back/day we ran a rail drag car/hilborne injected 302 chevy with a vertex mag, vertex recommended plug gap was .020''... in 'the fog of battle', we ran a set of plugs 'out of the box' at .035'' and lost a tenth, next pass closed same plugs to .020 and got the tenth back.
u chuz
