Changing Spark Plugs Question

[jfkelley]

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

[VileZambonie]

What plugs did you use?

[jfkelley]

AC Delco Rapid Fire #10

[bd]

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.

[JohnnyPopper]

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?

[bd]

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.