Author Topic: Changing Spark Plugs Question  (Read 1373 times)

Offline jfkelley

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Changing Spark Plugs Question
« 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
« Last Edit: June 25, 2019, 08:29:01 PM by jfkelley »
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline VileZambonie

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Re: Changing Spark Plugs Question
« Reply #1 on: June 26, 2019, 05:42:25 AM »
What plugs did you use?
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline jfkelley

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Re: Changing Spark Plugs Question
« Reply #2 on: June 26, 2019, 12:29:19 PM »
AC Delco Rapid Fire #10
1976 Chevrolet Scottsdale 4x4 ,K10 33” BF Goodrich All-Terrain .. in the middle of an LS swap LM7/4l60e/NP241C

Offline bd

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Re: Changing Spark Plugs Question
« Reply #3 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.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline JohnnyPopper

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Re: Changing Spark Plugs Question
« Reply #4 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?
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline bd

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Re: Changing Spark Plugs Question
« Reply #5 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.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)