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Spark Pllugs for Chevy 350

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  • Spark Pllugs for Chevy 350

    OMC recommends AC T43MR plugs. But this goes back many years.Does anyone know of higher performance plugs, i.e. more revs ,smoother idling? Platinum? Just put in some new Autolite equivilents and RPMs dropped by 200. Robert


  • #2
    Re: Spark Pllugs for Chevy 350

    Sure would help to know the year of your engine. Not all 350's are the same.
    Don S.

    sigpic

    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

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    • #3
      Re: Spark Pllugs for Chevy 350

      try this http://www.sparkplugs.com/results_cr...CrossWarning=1 It has all kinds of cross referenced plugs if your omc requires Delco MR43t spark plugs.Good luck

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      • #4
        Re: Spark Pllugs for Chevy 350

        The Chevy 350 is about an 1983 version. I nave the manual and its recommendation.Just wondered if some state of the art stuff might be around that folks knew about Thanks, Robert

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        • #5
          Re: Spark Pllugs for Chevy 350

          Bob, Car enthusizsts have a tendency to experiment with things... "SplitFire" or "Platinum" spark plugs, different wires, advanced timing, remaped fuel/air ratio etc...I have purchased my boat from a racer, who installed "SplitFire" plugs into pre-1986 350 Merc. When I got the boat, one engine was hidrolocked. When I took off heads, one head gasket was blown and the cylinder head had a crack. Top of pistons had grooves in them. The grooves looked like someone took an electrical welder and did a sloppy job welding the pistons.I asked the shop mechanic to look at it and determine the cause for problems.Verdict:"SplitFire" plugs caused an extra heavy spark which with time had caused damage to the top of pistons. Engine ran at hotest temperature at all times. Overheat caused blown head gasket which in turn caused water to enter cylinder. Unless Don S could contradict to this, I strongly suggest: Use what is recommended by MERC. Any deviation from OEM may actually harm the engine's parts in the long run. You have performance over damage on the scale... What's worse more is your call.

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          • #6
            Re: Spark Pllugs for Chevy 350

            Any deviation from OEM may actually harm the engine's parts in the long run.
            Just to refrase this: I think it only should apply to this particular case, case of spark plugs. Some changes from OEM as thruhull, less restrictive exhausts, better compartment ventilation, lighter weight manifolds and risers will by no means hurt the boat's engine. Don S, Bondo, please correct me if I am wrong

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            • #7
              Re: Spark Pllugs for Chevy 350

              Lenny, Thanks for your advise.I will stay with the manufacturer's call out on the plugs.It certainly sounds like a good idea based on your experience. Thanks, Bob

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              • #8
                Re: Spark Pllugs for Chevy 350

                I have been running AC RapidFire #1 plugs for 4 years and have never had one foul out. I do alot of Idling and I fog my engine after each use.

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                • #9
                  Re: Spark Pllugs for Chevy 350

                  There's All Kinds of Fancy Looking, Pretty Sparkplugs out there....... Most Co$t Much More than the MR43Ts,..............I've Never,.. Ever been failed, or let down by a MR43T Plug,..... Ever........I'd rather spend my money on somemore Gasoline,... Than Over-Priced SparkPlugs........That's My Opinion,........
                  Any Grease is Better,..... Than No Grease at All.......

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                  • #10
                    Re: Spark Pllugs for Chevy 350

                    Originally posted by Bondo: I've Never,.. Ever been failed, or let down by a MR43T Plug,..... Ever........
                    And I agree..........(but there is no way I will believe the BS about splitfires)

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                    • #11
                      Re: Spark Pllugs for Chevy 350

                      In Dennis Moore's book, "SBC Marine Performance", he recommends the extended tip versions of the MR43T, but I have only found the non-marine R43TS. NGK also has an extended tip version plug for the older 350 chevies. While his book has been out a long time and his explaination of why they are better, and seems to make sense, I have not heard testimonials on boating boards about using them. I did find that Crusader specs some for their 350 chevy's with the old style heads. The newer Vortecs do use an extended tip, as well. I have read on some other boating boards about a specific Champion plug that was designed specificly for Mercruisers 350's, because of a fowling problem. From what I can tell, it had something to do with the clearance between the plug and the exhaust manifolds. Apparently, the standard type is too close, picking up heat from manifold, and not being able to pull the heat away from the cyl head. It was also stated that if you replaced your plugs, every year, it wouldn't become an issue, and since they were Champions, I didn't figure it was worth trying.

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                      • #12
                        Re: Spark Pllugs for Chevy 350

                        Originally posted by Bondo Robby6950..........(but there is no way I will believe the BS about splitfires)
                        I will take a picture of the block that I have sitting in my garage. All components are 30 hours old. Engine ran with splitfires plugs. I would like to ask you Robby to comment on what will be on the picture (top of pistons) and maybe explain to me what might have been a cause for such damage within first 30 hours of using rebuilt block. It might as well clarify the BS - as you kindly expressed yourself in regards to my comments.

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                        • #13
                          Re: Spark Pllugs for Chevy 350

                          I'm calling BS on the splitfires, always did, always will. Spark only jumps to ground, and the easiest one at that............. SplitFire" plugs caused an extra heavy spark If your mechanic believes that a spark plug is making "extra heavy spark".....and you are here asking for a second opinion, well, you are getting one. The coil and Ignition system make ALL the juice, never the plug. 42 years of 350's and Harley's tell me that this guy raced these motors hot and on the edge of detonation, and those marks are melted aluminum from that, not the plug........run the 43's, everyone else does. And check the timing......

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                          • #14
                            Re: Spark Pllugs for Chevy 350

                            Well,................I Gotta Agree with Robby............Spark plugs,.......Any Sparkplugs,......... Even Sparkplugs that are Too Hot,..........Don't Burn Holes in Pistons..................Detonation,..... Spark-Knock,....... Pinging,..... Pre-Ignition,.........That's what Burns Holes in Pistons...............
                            Any Grease is Better,..... Than No Grease at All.......

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                            • #15
                              Re: Spark Pllugs for Chevy 350

                              Bob197, I was in no way trying to mislead you with what I said about SplitFires. My marine tech said SplitFires caused the top of pistons to melt...I would less likely stay with that version of the story. Bondo is a very knowledgeable and well known IBOATS forum member. I would listen and follow his opinion over my mechanics' as well as my own. Latest issue of Boating magazine suggested that "SplitFire Platinum" would increase both - speed and mpq by +0.75 and +0.25 respectively. I would like to apologize for giving you slightly wrong info. It is just that after I had to replace the block, I am a bit skeptical about none OEM parts. It was beyond my reasonable understanding how 30 hours of usage could kill 350 Merc engine. Mechanic mentioned SplitFires might have been an issue, so I replaced plugs to OEM recommended and decided to stick with it. I now remember running SplitFires in my Nissan Maxima. I tuned the car for performance and among the mods were sparkplugs. Did not hurt, but no visible power increase. On the other hand, free flow exhaust system, straight pipe in place of cat converter and a cold air intake was something of visual power increase. Robby, Bondo:Thank you for clarifying

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