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Which spark plugs for #46 Pontiac heads??????

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  • Which spark plugs for #46 Pontiac heads??????

    Hello Guys

    Been trying to find out what the correct spark plug would be for this head. All plugs broken off. Just left plugs base in the bores.

    Being in the UK, it seems no one over here can confirm for sure.

    A US parts supplier in UK told me that Champion #58 are the correct plugs. Yet when they arrived the plug body was too wide to allow the plug to fit the recess.

    I returned the plugs and they sent me some other back that did fit the recess and tighten up ok but the 'nipple' on th eplug feels loose when the suppressor cap is fitted - which makes me think that although they fit the plug bore ok, they may not be the correct plug after all.

    I am getting nowhere in UK trying to find out what is the correct plug so hoping you guys in US can advise this pretty soon.


  • #2
    Been told to stick with AC Delco plugs. But which ones...
    Holding me up getting engine started. Grrrr


    • #3
      Not sure what engine you have or what year. I went to and did a serch for your heads and they came back as being used on all sorts of engines. So I got my Motors Manual out and looked up '68 400 4bbl. and AC Delco 45S .035 gap, it also said for '69 GTO use R44S and all others use R45S. The R stands for resistor plugs so you don't have static on your radio.
      '65 Goat


      • #4
        Hey Buddy
        Thanks for the reply.
        The heads are number 46 with tapered seats. The block is a 71 (according to the code by dizzy) 455.
        Been told that 1969 heads with "46" on do not take tapered seat plugs (AC45TS) but take gasket type plugs. I recall checking the casting number which seemed to make them a 69 head but if the tapered seat on 73/74 is correct then they can't be 69 heads.
        All very confusing.


        • #5
          Yea Pontiac used that head casting number on a lot of engines from '69 400 and 428. Also in '73/'74's on 350's. If you have tapered seats it would be from a 350. Check the date code on the head to be sure. Here's a picture to show where the codes are. Date code is just below the valve cover.
          Attached Files
          '65 Goat