what spark plug to run?

Discussion in 'Engine Topic' started by hogg, Nov 7, 2017.

  1. hogg

    hogg Veteran Member

    3,083
    24
    Dec 29, 2000
    pegram,tn.,cheatam
    i have a 30 over 350,flat tops,64cc heads,old school double hump,polished out a little,2.02/160valves,488/488 lift cam, i do run reg.gas a lot, it don't like it, but it goes, I have been running the larger AC45 plugs,set at .450. They seem to foul out on me every once in a while, Is their a better plug i should be runing for this combo, Any input will be welcome.
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    8,811
    133
    Nov 4, 2004
    Ringgold, GA
    What's the ignition - points or hei? If points, that's too wide of a gap. You can also try a AC46 plug, that's next up in the heat range and may help clean it up. I personally like NGK but nothing wrong with AC Delco plugs.
     
  3. 70lt1z28

    70lt1z28 Veteran Member Gold Member

    1,169
    128
    Oct 3, 1999
    Beavercreek, Ohio, USA
    Like he ^ said.

    Also, whats the carb-jetting? Could be on the rich side.
     
  4. hogg

    hogg Veteran Member

    3,083
    24
    Dec 29, 2000
    pegram,tn.,cheatam
    Got hei ignition, I am doing a little tune up, clean out the 600 Eddelbrock carb, on top of a not so tall alum.intake, same jets as come with it.. The old heads ,68 double hump,take the large spark plug type. Can i put in the newer smaller spark plug in place of the older 45s big one? They seam to be the same lenth and deep ,thards but have smaller seats . The old big ones had a compress type washer, where the smaller ones do not. I'll look for the ones you said,witch ,NKG,? i can't seem to find any of the larger old 45s for sale any way.
     
  5. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    8,811
    133
    Nov 4, 2004
    Ringgold, GA
    You can't put the smaller plug in that head. I haven't bought any of those plugs in years so I'm kind of out of the loop. I'm certain the local parts stores can have them next day. There's nothing wrong with AC plugs, that's what I used on all my GM iron heads. I just got in the NGK camp when I went aluminum. A good rebuild on that 600 Eddy carb and a complete tune up should get you going. Make sure all items like cap, rotor, and wires are in good shape.
     
  6. Gary S

    Gary S Administrator Lifetime Gold Member

    20,631
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    Apr 14, 1999
    Bismarck, North Dakota
    The older plugs have a flat seat that used the compressed washer. The later plugs have a tapered seat. Putting the wrong ones in gives you a plug to head seat that doesn't fit and would be prone to leaking.
     
  7. hogg

    hogg Veteran Member

    3,083
    24
    Dec 29, 2000
    pegram,tn.,cheatam
    Yea, i was looking at then later after i posted. Flat ones have a little taper but i am thinking not enough taper to make them match up ,newer ones might even go in to deep. SO what is the best buy for these 40+year old heads ?I'll see what i can come up with tomorrow,The dis,coil ,wires are new,almost.
     
  8. COPO

    COPO Veteran Member Lifetime Gold Member

    15,847
    164
    Sep 15, 1999
    Ontario, Canada
    Use AC__S so they are deeper in the cyl if you have flat top pistons. I'm trying out AC R43S. I'm out in the Country and 99% of the roads are at a min speed limit of 50 mph which gets me close to 3k.
    I'm also running with a MSD 6AL 6420 and Crane XR-i in the dizzy. The MSD gets me a better burn and a better cruising feel. Plugs are currently gapped at .035 for my test. I tried .045 with my Autolite 86 plugs and had hesitation. The .040 gap worked on the 86's, but I'm going back to .035 for my test on the S plugs.

    R43
    [​IMG]

    R43S
    [​IMG]

    [​IMG]
     
  9. motorose

    motorose New Member

    29
    1
    Mar 14, 2009
    genesee wisconsin
    im running alum edelbrock performer heads, what plug with a flat seat are you guys using?
     
  10. wiseryder

    wiseryder Veteran Member Lifetime Gold Member

    1,887
    10
    Sep 11, 2004
    belding,mi USA
    I'm using NGK Fr4's in my RPM heads
     

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