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SBC 350 Exhaust popping after Replacing Exhaust Header Gakets, Flange Gaskets and plugs

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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.

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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 by jhm

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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

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