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Thread: 76 350 w/Vortec heads spark plug questions

  1. #1
    Senior Member myteemyk's Avatar
    Join Date
    May 2010
    South Central Idaho

    76 350 w/Vortec heads spark plug questions

    I have a 76 350 4bl that I had 97 Vortec heads installed on. The mechanic that installed heads/intake used NGK UR4 plugs (thats what the 76 350 used). Fast forward one year. All my plugs were beyond stuck and I broke one off attempting to get out. Is now fixed and all plugs loosened. I am going to replace the plugs with TR55's since everything I've searched leads me to believe the problem is the UR4's length was creating detonation right at the plug hole. All my boots are burnt/splitting right at the 90 bend.
    My question is, will using the 97 gap of .60 rather than the 76 gap of .45 make a difference?

  2. #2
    Full Member
    Join Date
    Oct 2006
    Which gap were you using before? You ought to stick with the gap recommended with the year of the motor, which would include your ignition module and coil/distributor...
    the smell of stale coffee, a bead of sweat in my eye, black grease under my nails...garage poetry...

  3. #3
    Senior Member myteemyk's Avatar
    Join Date
    May 2010
    South Central Idaho
    My mechanic had the plugs for a 76 350 gapped at the .45, but those were the wrong plugs. I have Vortec heads on a stock 76 350 block. We have determined the shorter reach on the 76 plugs played a part in them getting stuck in the heads.(Tips barely protruded into head,too much fire right at the hole. So I am changing his out for the 97 plugs which call for a .60 gap. Everything besides the manifold,carb,and heads are stock. I have switched over to manifold vac as it greatly improved idle,response,etc. I am going to switch out the springs,weights in the dizzy soon.
    My question is, should I gap the new plugs for the vortec heads (.60) even though everything else is stock, or should I leave the new plugs at .45 which is correct for a 76 350?
    I was told I would run into alternating scenarios like this when we decided to change heads.

  4. #4
    Senior Member
    gmctrucks's Avatar
    Join Date
    Nov 2006
    Look what members wrote on the other thread like this.

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