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    5.7 mercruiser rebuild...-gctid373285

    Looking to get the ultimate build for the money. Carb cam etc... anybody give me advice? This will be the boat i will have for years, would like to hit 40mph if needed... by the sounds of it, hes planning on putting it back to stock. Looking for options now, to make me happy for years to come. Once again, thanks guys!

    #2
    wow.im in the same boots but volvo and the same boat.i will be watching this thread

    Comment


      #3
      DMCB I believe can give you the best advise on the rebuild, especially the pistons and heads, I would not go too hot with the cam. Look up some of his posts, a lot of good advise posted, may be all you need.

      You might want to start with this one if it fits your engine. Mallory distributor.

      http://www.ebay.com/itm/251038878304...84.m1438.l2649

      I meant 2850bounty.
      Pat says: DO-IT-RIGHT THE FIRST TIME!

      Bayliner 3870 "ALASKA33)
      Twin 350 GM power
      Located in Seward, AK
      Retired marine surveyor

      Comment


        #4
        apexaro1 wrote:
        Looking to get the ultimate build for the money. Carb cam etc... anybody give me advice? This will be the boat i will have for years, would like to hit 40mph if needed... by the sounds of it, hes planning on putting it back to stock. Looking for options now, to make me happy for years to come. Once again, thanks guys!
        After reading your first comments, to build back to OEM would be a mistake, IMO.

        You can use a better piston by going to a quench style, and the cost to do so is not that much more.

        Nothing else to the build needs to be changed.

        .
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment


          #5
          2850Bounty wrote:
          After reading your first comments, to build back to OEM would be a mistake, IMO.

          You can use a better piston by going to a quench style, and the cost to do so is not that much more.

          Nothing else to the build needs to be changed.

          .
          Bounty, i mentioned the "quench" style build and even described the piston to the mechanic yet, hed never heard of it. He is the best in the area... ill get him some info.

          Comment


            #6
            It really depends on what you want out of an engine. Closed cooling? How much do you want to spend? What's the outdrive? 40mph is pretty fast for a 2750 but possible. 40 mph and stock engine don't go.together in the same sentence.
            1989 Avanti 3450 Sunbridge
            twin 454's
            MV Mar-Y-Sol
            1979 Bayliner Conquest 3150 hardtop ocean express.
            Twin chevy 350's inboard
            Ben- Jamin
            spokane Washington

            Comment


              #7
              apexaro1 wrote:
              Bounty, i mentioned the "quench" style build and even described the piston to the mechanic yet, hed never heard of it. He is the best in the area... ill get him some info.
              There are several piston styles that will provide the quench effect.

              The SBC engine was introduced in 1955 with a Quench Style piston and combustion chamber.... and it continued with this style combustion chamber for years.

              Only when the early 70's rolled around, and emmission control became mandated, did we see the silly full dished piston appear.

              That piston should be considered a Smog Control piston, and should not be used in a SBC Marine engine.

              But GM continued with this piston in many SBC's, including what we typically see in the GM Marine line SBC.

              You can ask your local libraray to bring in Dennis Moore's Small Block Chevy Marine Performance book.

              Dennis goes into detail on this.



              This is nothing new...., the Hot Rod guys and the Chrysler Wedge Head guys are also very familiar with this.

              The Q/E build for Marine is not so much for performance as it is to better reduce detonation potential.

              We can increase C/R slightly, change ignition advance some, and as a result we do pick up low end torque.

              .
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment


                #8
                i know to use this pistons instead of this

                Attached files [img]/media/kunena/attachments/vb/676728=26700-Dished%20Piston.jpg[/img] [img]/media/kunena/attachments/vb/676728=26701-trw-l2453f30.jpg[/img]

                Comment


                  #9
                  we all don`t want to end up like this

                  I am 1/2 inch from the "E" in texico on the map"

                  In the Tamps area, a man was asked his postition by the CG, after calling in disabled. Response " I am a vice president at XXXX bank


                  Comment


                    #10
                    Well, there's a tad bit more to it.... but yes!

                    The dish volume for the piston to the left will vary depending on other factors... bore/stroke/cylinder head, etc.

                    Small chamber cylinder head.... the larger the dish volume.

                    Large chamber cylinder head... the small the dish volume.

                    The equally important part is the flat surface that comes up under the wedge.... that's where the Quench occurs.

                    .
                    Rick E. Gresham, Oregon
                    2850 Bounty Sedan Flybridge model
                    Twin 280 HP 5.7's w/ Closed Cooling
                    Volvo Penta DuoProp Drives
                    Kohler 4 CZ Gen Set

                    Comment


                      #11
                      i read a lot of Your posts about engine rebuilt.i saved in my computer and i saved pictures.

                      i just want to make sure that i understand everything before i start asking ???

                      well im still confused but still reading

                      like apexaro1 and me we are confused

                      Comment


                        #12
                        Try to find the recent thread by our member "Giddy-Up".

                        He was the one who's engine suffered detonation damage and he was going to build a fresh one.

                        I went into detail regarding piston selection for a given bore/stroke/cylinder head chamber volume, etc.

                        See if you can find his thread.

                        .
                        Rick E. Gresham, Oregon
                        2850 Bounty Sedan Flybridge model
                        Twin 280 HP 5.7's w/ Closed Cooling
                        Volvo Penta DuoProp Drives
                        Kohler 4 CZ Gen Set

                        Comment


                          #13
                          well i will be honest.

                          im in bc canada and 99 % of the mechanics will tell u that they ca do marine engine but they will build a car engine with marine frost plugs and marine gaskets that`s all.

                          so i will have to figure out what do i want in my engine to perform for years on the water.it is sad but reality.las time i used canada engine in surrey bc and the engine last 6 months (1999 305 gm on 21 ft bayliner )i don`t think that in my region we have a good marine rebuilders

                          Comment


                            #14
                            my ? and i think LONE STAR is to keep the same engine or to go forward

                            Comment


                              #15
                              Gosh, this is such a big subject, it's impossible to cover it with just a internet blog. I think there are some key things that should be mentioned. It's important for the mechanic to realize that boats don't have gears. This fact will force some compromise in engine building that wouldn't be present in a car engine. You need torque from 2000-4600 and thats gonna be it. Other things to think about are the lack of vacuum needed, we don't have a brake vacuum tap, and the vacuum needed by the distributor(if you have a vac advance) is very small. This will impact the cam overlap and lobe centers. I would also ask your mechanic to investigate a dual pattern cam, where the intake lobe and the exhaust lobe are not the same. Boats seem to respond well to dual pattern cams because we generally set them at one rev and leave it there for a long time, and that rev number is quite a bit higher than would be found in the typical older car of the same displacement.

                              In a boat, we are using about 50-75% power when up on plane. In a car, going down the highway the typical V8 will only be using 20% or so of it's avail power. This makes a big difference in cam profiles, and also in lifter design. You may want to investigate the bleed down or anti-pump up type lifters that can provide a wider torque range and still offer good top end. Next, investigate a higher ratio(1.7) rocker arm than stock, and you might as well go roller rocker to reduce lifter wear, which can be a problem with boats which sit for long periods of time. Note that adjusting these valve components is critical to cam and lifter wear, so pay attention to the right preload value for the lifter and the rocker selected.

                              Next, I've always found that all things being equal, the head design is where the most gains in HP can be had. If we stipulate that you aren't going to stroke it out to 383 or something, then the best place to spend money is on the head. You can get larger valves, but this will affect low end torque some, you can get fat runners, large chamber, small chamber, you can get all kinds of things for the SBC engine these days. Here is a guy I've used before, but have no affiliation with:

                              http://www.racingheadservice.com/Cyl...y/Default.aspx

                              If you tell them what you are going to do, they will provide you with a set of heads and matched intake that will blow your socks off. Of course, nothing in life is cheap, and this is a good example of that. A pair of assembled heads in Aluminum ready to go is about $1300. Use with just about any hyperutectic piston which provides a 8.7:1 CR and I'm sure your boat will hit the magical 40 that you seek(with a good tuned SS prop).

                              There's a lot more to cover, but this hits the high points. The wide torque band needed kind of limits what we can do with cams, and intakes. Make sure the builder knows about lobe center differences, and how a dual pattern cam will scavenge better when set at one speed for long durations. The downside of that is many boats spend a lot of time near idle too, and some of these elements could make for a bit of a lumpy idle, and high emissions until you push the go lever. If you spend a lot of time at idle, take that into consideration with a smaller cam overlap. If you get in it, get out of the no wake zone and run it at throttle, then don't worry about that. If you spend a ton of time at idle or 1200 revs, that could be a consideration.

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