Plugs for Edelbrock Heads?

Discussion in 'Street/strip 400/430/455' started by knucklebusted, Apr 7, 2021.

  1. knucklebusted

    knucklebusted Well-Known Member

    Here's a typical plug in my engine. It was starting to have a low speed intermittent miss that cleared up with RPM. These were NGK R5671A-9. I have no idea why I bought those.

    They look a little rich and probably a lot cold.

    I just bought a set of Champion RC12YC that Edelbrock recommends for their heads.

    What does anyone else run in an Edelbrock head and have good luck with? 9.5:1 compression, TA212 cam, headers, Q-Jet that might need to be leaned out.

  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The NGK R5671A-9 is a recessed electrode race type plug. I would never run a plug like that in a street driven vehicle. The FR-5 is a projected nose plug and offers a lot of advantages for street cars. The Champion plug is very similar.

    NGK plugs have plated threads, great for aluminum heads, no anti seize necessary. Edelbrock heads use the same plugs as TA heads, flat seat, 3/4" reach.
    knucklebusted likes this.
  4. Bens99gtp

    Bens99gtp Well-Known Member

    I run 7173. But I have closer to 12:1 on mt ta heads
    knucklebusted likes this.
  5. knucklebusted

    knucklebusted Well-Known Member

    How I arrived at that plug, is unknown. They ran OK for 4 full years until this season when they started having a low speed misfire. I think a hotter ignition/MSD probably masked many issues.

    I'll take the Champions back and get the better NGKs.
  6. Bens99gtp

    Bens99gtp Well-Known Member

    There is only minor difference in the 7373 vrs 7173 is the 7373 is a heat range 5 with a 5k resistor. The 7173 is a heat range 8......colder in ngk terms.....and a 1k resistor.
    The gap on 7373 is .008 larger from the factory..... 039 vrs 031
    knucklebusted likes this.
  7. Stevem

    Stevem Well-Known Member

    When you get the right extended nose plug in the motor you will likely find that atleast at large throttle openings you will need less timing and your idle might clear up some also!
    knucklebusted likes this.
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    FR-5 is the plug Jim Weise uses in most of the engines he builds I believe. Last I heard anyway.
    knucklebusted likes this.
  9. Jim Weise

    Jim Weise 1000+HP

    Up to 11-1 compression I use the FR-5 (NGK Stk number 7373)

    12-14-1 gets the R5672A-8 plug (7173)

    Boosted motors will get an this 8 or possibly the 9 heat range version.

    Plugs for our motors are pretty simple

    Lower compression iron heads.. up to 9.5 to 1.. Use NGK UR 4 or 5 (6630 or 2771)

    Higher compression Iron heads-- NGK UR6 (7773)

    Alum heads NA applications below 11-1 FR-5 (7373)

    Alum head 12-14-1 gets the R5672A-8 plug (7173)

    Alum head Boosted motors will get the R5672A-8 or 9 or even the 10, depending on what is going on.. (7173, 7405, 7942).
    Last edited: Apr 8, 2021 at 7:27 AM
    knucklebusted likes this.
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You may have trouble finding them in your local parts stores. Rock Auto has the best price on them I believe. 1.55/plug. Edit, I just looked and most sources want double that. Jegs was the next cheapest at 2.49.:rolleyes:,7373,spark+plug,7212
    Last edited: Apr 8, 2021 at 7:27 AM
  11. knucklebusted

    knucklebusted Well-Known Member

    Time delay is the problem. A good deal next week doesn't beat driving it today. I can get them for $25 at O'Reillys.
  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yup, 3.00 + per plug is what I am seeing. If you like them, stock up at RA.

    I think you will see a big difference in the way the engine runs.
    knucklebusted likes this.
  13. sriley531

    sriley531 M.M.O.G.

    Fwiw I use FR-5's in my eddy heads and they work as they should.
    knucklebusted likes this.
  14. Schurkey

    Schurkey Silver Level contributor

    That plating works fine, once. How is it the second, third, fourth time you pull the plugs out?

    I like anti-seize.
    knucklebusted likes this.
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The only time I pull them out is to change them. Anti seize is fine as long as you don't pile it on to the point it interferes with heat transfer.

    Not sure about repeated removal install of the same plugs. Might be a question for NGK.
    knucklebusted likes this.
  16. knucklebusted

    knucklebusted Well-Known Member

    As Larry said, I only pull them out when in doubt and about to change them.
  17. Jim Weise

    Jim Weise 1000+HP

    Who the plugs out 4 times?

    When I worked for an OEM that used NGK/Nippondenso plugs from the factory, we were instructed to NOT put anti-seize on the new ones, during major services. There was a long technical internal training video done on the causes of plug seizure, and on how any compound on the plugs inhibits heat transfer, thus making seizure more likely.

    unless your taking them out ever other week, just to make sure they still have an electrode on them...

    The rest of us might have a plug in a hot rod street motor, that is used lightly, for years, if not decades.. Cars like this spend more time sitting, than driving.

    knucklebusted likes this.
  18. knucklebusted

    knucklebusted Well-Known Member

    Installed and started after 2 pumps.

    All is good with the world... Now, if I could just get my 350 machining done.
    john.schaefer77 and Max Damage like this.

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