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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: jfkelley on June 25, 2019, 08:16:44 pm

Title: Changing Spark Plugs Question
Post by: jfkelley on June 25, 2019, 08:16:44 pm
You guys are great at providing very useful information, and I have a new question...So before I gave my son the truck I changed the spark plugs in it ...The "Kid" 2 O'reillys sold me the plugs and said to gap them @ .045 ...Is this correct gap for an 1976 Chevrolet K10 400 CID , Should I move the GAP to .035..?...it seems like its harder to start since changing the spark plugs...Any thoughts?q
Title: Re: Changing Spark Plugs Question
Post by: VileZambonie on June 26, 2019, 05:42:25 am
What plugs did you use?
Title: Re: Changing Spark Plugs Question
Post by: jfkelley on June 26, 2019, 12:29:19 pm
AC Delco Rapid Fire #10
Title: Re: Changing Spark Plugs Question
Post by: bd on June 26, 2019, 03:44:31 pm
It always struck me as odd but Rapid Fire plugs generally don't perform well.  You would be better served by using CR43TS if the old plugs were burning clean when removed.  Otherwise, use R45TS.  Both should be gapped to 0.045".  The 0.035" gap was used for GM conventional ignition engines and for TBI engines.
Title: Re: Changing Spark Plugs Question
Post by: JohnnyPopper on June 26, 2019, 05:47:11 pm
It always struck me as odd but Rapid Fire plugs generally don't perform well.  You would be better served by using CR43TS if the old plugs were burning clean when removed.  Otherwise, use R45TS.  Both should be gapped to 0.045".  The 0.035" gap was used for GM conventional ignition engines and for TBI engines.

Before HEI?
Title: Re: Changing Spark Plugs Question
Post by: bd on June 26, 2019, 07:14:23 pm
The gap used on most HEI LD truck engines (the 3.8L V6 was an exception) was 0.045".  Pre-HEI and TBI used 0.035" gaps.