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Old 07-19-2019, 11:23 PM   #8
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Join Date: Feb 2009
Location: Northern Nevada
Posts: 4,756
Re: Correct Spark plugs?

Originally Posted by Steeveedee View Post
That's a lot of plugs! Did the 402 get the taper seat plugs in '71? Mine still has the N-type 14 mM long reach.
Factory 402 heads take the tapered plug. That's not to say GM never built one otherwise. So 71 is generally correct. If I recall, there was a slow transition 396 to 402, which occurred in some 1970 The trucks are badged 396, but have 402 blocks. Makes me ponder if GM assembled "396" heads on 402 blocks

I can't speak for all 396 heads, mine came off a 68 HP Camaro. They generally or always take the flat-seated gasket type plug.

71 C10 Custom Deluxe, SWB, fleet, 402/400TH, A/C...Resource intensive......And (*^(*^ leaf springs. Speak of, looking for OEM rear sport bumper brackets for this ride. They're unlike those more common, even the outer brackets are different.

72 Cheyenne Super, LWB, fleet, C20, 402/400TH, A/C. Driver and tinker truck
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