First plug change.

Big Block A body Tech

  1. beanhead

    beanhead Well-Known Member

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    I have put 362 miles on my newly-built 505", so I pulled the plugs for an autopsy and replacement. These are NGK BKR5E, been in since initial fire-up and the subsequent driving.
    Moving the timing and tune around some, working through the carb it's an older speed demon 850 mechanical-secondary and I've added replaceable air bleeds and PVCR's since they were all fixed on this model. I had it on my last engine too (440) and had it pretty well nailed, this time I'm thinking I might wanna add brass in the IFR's. First drive of the day, even here in the heat it seems to go real rich as soon as I crack the throttle, and stays that way while cruising even at higher speeds (3000 RPM) BUT--after a shutdown/heat soak and another trip, the AFRs creep up and stabilize around high 13s-14 at cruise and in the transition area which is better on the gauge but I'm not thrilled with the plugs and that's all I really care about at this point.
    WOT is fatty but I'm not really dealing with that yet. Even up close the thread coloring plays tricks on my eyes but they seem like they could've been a step warm so I have 6's in it now.
    It's a 'relatively' mild 250 @ .050 solid FT cam, 112 LSA in at 109. Timing is 22/34 by 2500 rpm and I run the ported advance to start pulling in around 15" which gives me 48 total before the engine maxes out the vacuum. Maybe a little conservative now but it seems happy with that. Idles at 850 with about 8" vacuum and pops up to 12" when I crack the throttle, then cruises between 14"-20". The revs come up real quick while cruising with the 9.5 converter and a 10.5 gave it just a bit of a rich hit in traffic so I'm running an 8.5 PV now with the jets at 82/89 (stock was 85/92). Whatcha guys think? Thanks!


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    (some of the gunk on the very tips is from my dirty gloves--lol)
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  2. yellow rose

    yellow rose Master Of Insanity

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    You need to add T slot restricters and probably open the main air bleed up .004-.006. I’d do the T slot restricters first, using 10x32 3/16 brass and Id start with an .078 hole and tune from there.
     
  3. beanhead

    beanhead Well-Known Member

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    Thanks. Leave the IFR as-is? I think they're set at .035 but I may not be remembering that right.
     
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    • famous bob

      famous bob mopar misfit

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      Interesting , I started w/ 7`s ,and went to 6`s (ngk) ,and have leaned the fuel inj. everywhere and still looks a little rich -----------
       
    • Kern Dog

      Kern Dog FABO Gold Member FABO Gold Member

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      Did you cut off the threaded parts to show the porcelain or am I just confused?
      If so, you've gone WAY further than I ever have at plug reading!
      Beanhead Plymouth.jpg
       
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      • yellow rose

        yellow rose Master Of Insanity

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        Yes, that’s the best way to see what’s going on.
         
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        • yellow rose

          yellow rose Master Of Insanity

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          The .035 IFR sounds big, but without knowing the IAB it’s hard to say.


          Also, if the IFR’s are located at the top of the metering block, you can lower them, and you probably should. Virtually every carb I’ve done wanted them lowered, except two, and one was mine.

          I can’t explain why mine doesn’t like the IFR lowered, but you just have to give the thing what it wants.
           
        • 512Stroker

          512Stroker We are all here because we are not all there.

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          Those plugs are cold - barely burned into the first thread
          IMO they look lean for a street application - I like to see a little more color for a safe all conditions driving.
          I cant even see a timing indicator on the ground strap. What's up with that?
          Any indication of detonation when driving?
           
        • yellow rose

          yellow rose Master Of Insanity

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          It’s pump gas. They look ok except for transition and WOT.

          The difference from left to right can be distribution issues or just a rich condition that will clean up with some tuning.

          On pump gas I don’t mind running the heat Mark to the shell.
           
        • beanhead

          beanhead Well-Known Member

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          Yep all the way off!
           
        • beanhead

          beanhead Well-Known Member

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          I need to re-pin the bleeds to measue but it seems like the idle air bleeds were up around .080. Need to verify though I'll do that today.
          IFRs are factory fixed holes but in the low position, here's a metering block--3 emulsion bleeds, made before the high-ifr got popular among the manufacturers I guess.
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          Last edited: Sep 16, 2020
        • beanhead

          beanhead Well-Known Member

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          It's there but can't see it in every pic, and I noticed one plug in the pictures the strap just looks kind of dark and evenly colored so yeah that is weird. I haven't heard or felt any knocking though.

          I should have added this is a 10 to 1 SCR, zero deck pistons with a .039 quench distance.
           
        • TrailBeast

          TrailBeast AKA Mopars4us on Youtube

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          I totally get where you are going with your carb because I did exactly the same with my 770 avenger but manually because it doesn’t have adjustable bleeds.
          The transition bleeds were rich, but when I got it leaned down to the AFR I was shooting for the motor acted a bit weak and glitchy just off idle.
          So instead of chasing an AFR I switched to giving the motor what it was happy with.
          A little rich on the idle and transition and in the mid 13 to low 14’s at hiway cruise.
          In my opinion it runs just sweet as it can be.
          In my own opinion your plugs look well into the “safe“ zone.
          One step hotter should be ok as well.
          I also think it’s annoying that carbs change from one drive to another.
          My Edelbrock carb would idle super lean after a shut down and restart for a couple of minutes.
          The Holley 770 does the same thing though not nearly as much.
          I guess the main point I’m making is to get it close using AFR’s, then give it what it likes from there.:D
           
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          • beanhead

            beanhead Well-Known Member

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            IAB .073
            HSABs are .030 pri/.033 sec
            .059 PVCR
            The air around here's been so bad I haven't wanted to do much after work but it's improving so I want to get out for some test drives the next few days. Thanks for the input guys, gives me some good ideas on what to look at first.
             
            Last edited: Sep 17, 2020
          • RustyRatRod

            RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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            Yeah, it's the only way to see "the whole story". Farther than I've ever gone too.....but then again I've never had a 505 either. lol
             
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            • yellow rose

              yellow rose Master Of Insanity

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              Roughly, if the IFR mentioned above is correct, I’d either be about .008-.010 bigger on the IAB or down to .029-.030 on the IFR.

              When you get the idle circuit clean like it should be, you’ll have to fix the rest of it...it will likely have tip in issues and at the end of transition it will go rich, so that’s where the T slot restricters come in the most.

              The smaller the MAB the later the booster gets going, and the fatter the fuel curve will be at RPM. The larger the MAB, the quicker the booster starts, and the leaner the fuel curve will be at RPM.

              One interesting thing...and I’m fighting it right now myself is with lots of cam timing and relatively low idle vacuum you get another issue that acts like a lean tip issue, but it’s really a rich condition.

              Once you are moving and the vacuum goes UP, but you are still on the idle circuit, because the vacuum signal is greater...you are now back to rich going from idle to transition, just like you’ll be rich from transition to the mains! This can get you in the weeds (I’m still in the weeds but they are no longer strangling me...I’m starting to get a handle on what’s happening) and drive you nuts.

              This is magnified with a tunnel ram, but still a issue with single 4 stuff. What may “drive” and “feel” like a lean spot from the idle circuit to the T slots is really a rich condition, because the signal (i.e. the vacuum is higher but you are still on the idle circuit) is much better.

              It can be hard to wrap your head around this, but it is true. Lucky for me, I have the BEST carb mentor, who is willing to help me along.

              Otherwise, I’d be screwed.
               
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              • beanhead

                beanhead Well-Known Member

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                This is what I suspect is happening too. Idles in gear with 8ish in/hg and immediately jumps to 12 or so with some throttle which I'm sure starts sucking a bunch of fuel.
                 
              • SuperStock426

                SuperStock426 Well-Known Member

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                That 8.5 power valve is a bit high I would think. I would think you'd need one 3.5-4.5. How much vacuum is your engine producing? I'd recommend the AR3911 Autolite spark plugs depending on which cylinder heads you're using.

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                Last edited: Sep 17, 2020
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                • beanhead

                  beanhead Well-Known Member

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                  Well, I'm a firm believer in running the PV closer to cruise vacuum. I average 13-17" vacuum with max up to 20" at cruise depending on speed and the only reason I pulled the 10.5 PV out was it came in a hair too soon when stabbing the gas at 30-ish mph. But, with things down low still a bit outta whack, once I get the transition area dialed it may go back in because I suspect I wasn't completely on the boosters yet. I like to get a leaner PMJ setting and have the PV enrich at the instant I get on the gas from the main-circuit cruise. I realize everyone has different ways of getting the job done though, and I do appreciate your input! Thanks.
                  I currently have Edlbrock RPM heads, they recommend starting with RC12YC champs. With the same heads and a little less SCR on my 440s I used to run autolite 3924 before switching to the NGK 5, and they worked good.
                  I love this stuff!
                   
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                  • yellow rose

                    yellow rose Master Of Insanity

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                    You are probably really close with the 10.5 unless you don’t have T slot restricters. As the throttle blade opens the T slot gets richer, and that’s when the PV starts to open so it looks and IS rich, but not because the PV opened up, but because the T slot is too rich.
                     
                  • fishmens67

                    fishmens67 Well-Known Member

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                    I'd go 1 step hotter on the plug
                     
                  • beanhead

                    beanhead Well-Known Member

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                    Gettin' there...next set of plugs. BKR6E, one step colder than the last, still a standard .035 gap. 100 miles of street driving, with 4 "passes" on the secret country dragstrip right before I pulled them. No clean-cuts at the top or anything but I'm getting a good glimpse..


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                    Richest one
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                    Leanest one. Yeah I broke it..
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                    I'm getting plating color change on 1-2 threads so the engine's liking the heat range. NGK's read heat a little different but it's easier to see in person.
                    I bumped the IAB's way up to see what a big swing would do, went .078s, and it leaned things out but took power and response with it, after re-adjusting the base settings. So, before pulling the blocks to change anything internally I wanted to test one more thing and went to .070 IABs and .031 MABs, BUT closed my secondary T-slots up just a quarter turn from .020 and bumped the idle timing to 24 to get the RPM back to 850. Now at 24 intial, up from 22 and my total is actually only 32. I reported it at 34 last time but I put a timing tape on my shiny balancer (Romac) and now I'm seeing things more accurately..
                    The T-slots come down to the same level on this (4-corner) carb, and I remember back in the day BG recommended setting them all the same, then later they said "close the rear slots for engines that idle under 1000 rpm, open them square if idling above 1000..." then later changed again....so apparently even they weren't sure lol.
                    Since I'm dealing with the primaries mostly for now anyway, I got thinkin' maybe the rear slots are just bleeding extra un-needed fuel during the transition period...seems to have leaned me out without losing the ability to push the ass end into the next lane at 30 mph LOL. I know, but the kids love it:p

                    I'm liking the idle and cruise now but it's a bit lean under power as you can see. In addition to the plugs, the gauge says 13.1/ 60mph cruise. 13.8-14.0/40 mph cruise, which is where this car spends most of it's time. I know it's modern unleaded, so it doesn't color up quite as fast but I'd like to see a little more at the bottom. Now I may go back to that 10.5 PV and see how she flies.
                    Oh....my ford buddy gave me some Champion plugs out of his stash, a mix of 12 and 10 heat range and I'm gonna compare the results to these NGKs. I prefer the NGK but Champs are a little easier to read sometimes, I think..
                     
                    Last edited: Sep 26, 2020 at 12:27 AM
                  • beanhead

                    beanhead Well-Known Member

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                    And check this out. When I'm cruising along and I floor it, trans kicks down and the car rockets on down the road...and the A/F drops to 11.7-12.0 and stays down there. But, from a slow creep or stop if I nail it and go through the gears manually (taking care not to blow the tires off too bad at the bottom end) the gauge runs steady in the 13.7-14 range all the way to pucker-and-lift. What's up with that? Gearing/load related? I figure WOT is WOT as long as things have a chance to stabilize, but the two situations are producing different readouts....
                    It absolutely hauls balls shifting manually at WOT but the plugs seem to correlate more to the high 13's on the gauge than the 'stomp from a cruise' numbers.
                     
                  • 512Stroker

                    512Stroker We are all here because we are not all there.

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                    Just like your first set of plugs they still look cold and lean IMO.
                     
                  • yellow rose

                    yellow rose Master Of Insanity

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                    They look cold to me too, but not lean to me though. It looks like it’s rich on the transfer slots or he may be able to drop the primary main jet a couple of numbers and then open up the power valve channel restricters if it’s lean at WOT.


                    Many years ago, I read an NGK article, or maybe it was in the catalog or something, but it said for heat range you want 2-3 threads showing color.

                    Champions I don’t go much over 1 thread. The playing on the two plugs are different, but, IIRC in the end they both end up running at the same heat load. So either Champion uses a higher temp plating than NGK, or NGK uses a lower temp plating.

                    However that works. It’s damn sure confusing. Just looked at a set of AC plugs yesterday, and they look really nice, but I have no idea what plating they use, so I’ll use them and see what they look like.
                     
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