Miles Posted November 13, 2018 Share Posted November 13, 2018 1972 240Z New Goodwrench crate SBC 350 Holley Carb Hooker block hugger exhaust headers Build date: 2009 Approximately 6,000 miles on build Holley carb, MSD HEI distributor and timing not touched since dyno tune 2009 Car ran fine for nine years , but developed a recent exhaust header leak. Replaced header and flange gaskets and, while I was at it, also replaced the plugs - Accel shorty Plugs gapped at 0.035 At start up, the exhaust makes popping sounds at idle after five minute warm up. No popping when cold. Gets worse the longer the engine idles. Popping gets louder with warm up and is punctuated by a very loud POW at random times. No other changes were made. Checked: Plug wires not mixed up. No arcing around plugs or wires Plug wires tight on plugs and distributor cap Re-tightened header and flange bolts. Quote Link to comment Share on other sites More sharing options...
jhm Posted November 13, 2018 Share Posted November 13, 2018 (edited) Weird. I've used those same plugs for years without any issues; but IIRC, gap them a little larger....maybe 0.043"? Plug gap too small might be the root cause of the issue. Edited November 13, 2018 by jhm Quote Link to comment Share on other sites More sharing options...
Miles Posted November 13, 2018 Author Share Posted November 13, 2018 1 hour ago, jhm said: Weird. I've used those same plugs for years without any issues; but IIRC, gap them a little larger....maybe 0.043"? Plug gap too small might be the root cause of the issue. I'll reset the gap. Thanks Quote Link to comment Share on other sites More sharing options...
Miles Posted November 13, 2018 Author Share Posted November 13, 2018 jhm Reset gap to 0.045. Worked perfectly. Thanks 1 Quote Link to comment Share on other sites More sharing options...
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