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Stroking a volvo penta 5.7

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  • Stroking a volvo penta 5.7

    I am in the position that the engines in my boat need replacing because of age. They run good, smoke alittle and hard to start. Thinking about stroking them out to 383cu. Anybody done this before? I have had good results in hot rods but i have not seen anything in a boat. I need a better cam for a 383cubic inches. Any suggestion is appreciated. Working on a 1990 chaparrel 2750 sx w/twin VP 5.7s duos

  • #2
    Ayuh,..... Welcome Aboard,..... Sounds like Fun,......

    Vortec heads, block decked to 0, d-dish pistons to hold the compression ratio to 10:1,.....
    With the headgasket, you'll be gettin' perfect quench, 'n gobs of horsepower, 'n flat torque,.....

    Comment


    • #3
      My opinion is buying 383 long blocks is considerably more expensive than getting 350 long blocks, like almost double the price for only ~10% more displacement. One can look at Summit and Jegs and others for possibilities. You'd probably have to pull the core plugs and replace with brass for marine service.

      There are some internal clearance issues because of the 383 stroker crankshaft and the cam has to be carefully selected so things don't strike if you are buying a short block and intending to put on your own heads.

      The long stroke is a great recipe for low-end torque but its also directionally wrong for an engine you want to run at peak speeds. Like anything in life there is (good, fast, cheap) and we only get to pick 2.

      Comment


      • #4
        Hey Scott Danforth want to add anything
        94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
        95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
        07 Seadoo GTX
        Merc Adults Only VP Adults Only
        G-Dad always said "First Liar doesn't stand a chance"

        Comment


        • #5
          build the motors yourself.

          the rotating assembly of a SBC is only about $15 more for a 3.75" stroke than a 3.48" stroke

          if you go new

          prices I found as of end of last month
          New GM block is about $1100 p/n 10105123 with all the rebates (the pre-clearanced block 88962516 for stroker cranks is about $100 more)
          New GM vortec heads are about $850 a pair
          New SCAT stroker rotating assembly with KB pistons is about $950
          New felpro gasket set is about $175
          New comp cams XM-264HR K-kit $950
          New summit 1.52:1 roller tip rockers $100
          new melling oil pump, pump shaft, and core plugs $75
          new ARP head studs / main studs

          i would run an RPM air-gap intake, a 2" carb spacer and at least a half system heat exchanger.

          with a cam, you need to stick below 270 degrees of duration or you suffer reversion

          Note: Mercruiser uses 1.6:1 rockers with their 6.2 builds using the same cam that they use in the 5.7's Not sure what VP uses, however I know its a different cam
          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

          Past Boats
          1970 Wooster Hellion - Merc 9.8
          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

          What’s behind you doesn’t matter.Enzo Ferrari

          Comment


          • #6
            Yes, that's about what I was thinking, added all up thats ~$4300. I have it in my head that a 350 long block is in the $2200 range. I was considering a 383 for a tired 350 truck engine recently and started some initial research.

            I do really like the comp cams roller pivot/roller tip rocker arms, its a 4130/4140 steel rocker arm instead of an aluminum one. I have put them into all trucks thus far. Does a lot when you have a flat tappet lifter engine (non roller-lifter).

            Comment


            • #7
              Originally posted by Saline Marina View Post
              Yes, that's about what I was thinking, added all up thats ~$4300. I have it in my head that a 350 long block is in the $2200 range. I was considering a 383 for a tired 350 truck engine recently and started some initial research.

              I do really like the comp cams roller pivot/roller tip rocker arms, its a 4130/4140 steel rocker arm instead of an aluminum one. I have put them into all trucks thus far. Does a lot when you have a flat tappet lifter engine (non roller-lifter).
              the summit roller tipped rockers are comparable at half the cost.

              you can get a new 350 long block for $2098 from Scoggin Dicky. however its not a stroker, and it has flat top pistons with 4 relief cuts. its end-of-run GM truck motors that never made it to the truck plant. so you could strip it down, throw away the rotating assembly and go from there. however your not gaining much, and you need to run an electric fuel pump vs the GMPP blocks I listed above.

              about a year or two ago, the blocks were only $750 and a new pair of vortec heads was $600

              if you want to save money, get a 96-2000 GM truck motor for $125 from the local pull-a-part, sink $250 into the heads, use only the block (tossing the rotating assembly) , line-hone, deck, bore and hone (machine work will be about $6-800), then buy a new Scat rotating assembly, and a new Comp Cams K-kit........you save about $400-600 going that way

              then again, you can build a big block for just a few hundred more.
              Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

              Past Boats
              1970 Wooster Hellion - Merc 9.8
              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

              What’s behind you doesn’t matter.Enzo Ferrari

              Comment


              • #8
                385 PERFORMANCE TUNE – ENGINE ONLY 8M0064807 385 Performance Tune Bravo Sterndrive Engine Only. 350 HP @ 5200 RPM. 385 Cubic Inch Stroker Fully Dressed Marine Engine. Engine Features: Remanufactured 4.040" Bore GM 4‑bolt Main V8 Marine Iron Block, Multi‑Port Fuel Injection Using Cool Fuel II, Dry Joint Exhaust, 100 PSI Oil Pump, 4340 Forged Steel Crankshaft, H‑beam Forged Steel Connecting Rods, 9.0:1 Forged Pistons, Special 302 Windage Tray, Mercury Cylinder Heads Machined with Rocker Studs, Multi‑Layer Steel Head Gasket, High‑Lift Billet Steel Camshaft, Stainless Steel Intake Valves, Nickel‑Alloy Exhaust Valves, Copper Oil Cooler, Oil Thermostat, Remote Mount Gear Lube Reservoir Kit, Water Pressure Relief Valve Kit, and 1.6:1 Full‑Roller Rocker Arms. The 385 PT uses ECM555 with Engine Guardian and is SmartCraft ready, 10‑Pin Harness. Flame cover not included. By design, oil consumption of one or more quarts every 5 hours may be typical. Fresh Water Cooling not recommended ‑ call for further application assistance. 350 HP Remanufactured Sterndrive Engine Replaces 383 Mag Stroker MPI sterndrive engines


                I was surprised to see this engine in the Mercury repower catalog. only $14,156.25 and by design it could burn one or MORE quarts of oil per 5 hrs of operation? Not sure whats up with that, but a least they note it in the catalog.
                Good Luck Muc

                Comment


                • #9
                  This is the rocker arm I was thinking of...roller pivot/roller tip. Theres a fair amount of friction in the ball-pivot although it is quite simple and reliable.

                  https://www.compcams.com/ultra-pro-m...2-ratio-5.html

                  Comment


                  • #10
                    Originally posted by muc View Post
                    385 PERFORMANCE TUNE – ENGINE ONLY 8M0064807 385 Performance Tune Bravo Sterndrive Engine Only. 350 HP @ 5200 RPM. 385 Cubic Inch Stroker Fully Dressed Marine Engine. Engine Features: Remanufactured 4.040" Bore GM 4‑bolt Main V8 Marine Iron Block, Multi‑Port Fuel Injection Using Cool Fuel II, Dry Joint Exhaust, 100 PSI Oil Pump, 4340 Forged Steel Crankshaft, H‑beam Forged Steel Connecting Rods, 9.0:1 Forged Pistons, Special 302 Windage Tray, Mercury Cylinder Heads Machined with Rocker Studs, Multi‑Layer Steel Head Gasket, High‑Lift Billet Steel Camshaft, Stainless Steel Intake Valves, Nickel‑Alloy Exhaust Valves, Copper Oil Cooler, Oil Thermostat, Remote Mount Gear Lube Reservoir Kit, Water Pressure Relief Valve Kit, and 1.6:1 Full‑Roller Rocker Arms. The 385 PT uses ECM555 with Engine Guardian and is SmartCraft ready, 10‑Pin Harness. Flame cover not included. By design, oil consumption of one or more quarts every 5 hours may be typical. Fresh Water Cooling not recommended ‑ call for further application assistance. 350 HP Remanufactured Sterndrive Engine Replaces 383 Mag Stroker MPI sterndrive engines


                    I was surprised to see this engine in the Mercury repower catalog. only $14,156.25 and by design it could burn one or MORE quarts of oil per 5 hrs of operation? Not sure whats up with that, but a least they note it in the catalog.
                    Muc, OP has a volvo with holley carbs and most likely DP-A drives. not sure why he would want to spend $28k on a pair of Mercruser motors when he can build a stroker, use his existing exhaust, carb, accessories, electrics and do both motors for about $9k about $10k if he needs new exhaust

                    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                    Past Boats
                    1970 Wooster Hellion - Merc 9.8
                    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                    What’s behind you doesn’t matter.Enzo Ferrari

                    Comment


                    • #11
                      Originally posted by Scott Danforth View Post

                      Muc, OP has a volvo with holley carbs and most likely DP-A drives. not sure why he would want to spend $28k on a pair of Mercruser motors when he can build a stroker, use his existing exhaust, carb, accessories, electrics and do both motors for about $9k about $10k if he needs new exhaust
                      Sorry, I wasn’t recommending that engine to the OP. His first post made me think that he wasn’t aware that a small block stoker had been done in a marine engine. It has and is so common that MerCruiser offered it both stock and as a Repower.

                      The engine i listed caught my eye when it came up doing research for a client and I just couldn’t help myself. One or MORE qts per 5 hrs and only 350hp?

                      The post was also a warning to be careful when selecting components for his rebuild. Even MerCruiser was able to build a engine that produced less then 1hp per ci. and it burns oil?
                      Good Luck Muc

                      Comment


                      • #12
                        The post was also a warning to be careful when selecting components for his rebuild. Even MerCruiser was able to build a engine that produced less then 1hp per ci. and it burns oil?
                        Very good points

                        It did get me that Merc states it can burn oil, and my 530hp 509 doesn't burn enough to notice between changes
                        94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                        95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                        07 Seadoo GTX
                        Merc Adults Only VP Adults Only
                        G-Dad always said "First Liar doesn't stand a chance"

                        Comment


                        • #13
                          Thank you for all the help. I think i have found the way i am going to go. I found a blueprinted 383 completely dressed and dyno tested at "Jegs". It is sold as dynoed at 405hp and 450fp of torque. They run at $6000 each alittle pricy but should be fool proof. Does anyone know anything about these?

                          Comment


                          • #14
                            It is sold as dynoed at 405hp and 450fp of torque.
                            Ayuh,..... What's the cam's spec's,..??

                            Comment


                            • #15
                              Sign up today
                              Hey muc, all good. thought you were recommending the motor.

                              I agree with both you and AD, a qt of oil in 5hours is alot. especially since 350hp at the crank is a mild build with stock cam. if you dont gap your rings right, they will smoke and suck oil. running stock umbrella seals doesn't help much

                              the 1.6:1 rockers with stock vortec heads echo the stock cam or there would be coil bind.

                              no need for forged pistons in a 383 unless you plan on running a blower or are balanced to spin above 5500 rpm

                              hypers are fine for most boats. stay away from eagle cranks and rods (talk to your machinist here) SCAT is really good for an off-shore product.

                              now if the OP wants to build a pair of 450hp, 5500 RPM screamers, I would go forged. the VP drives will handle it.
                              Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                              Past Boats
                              1970 Wooster Hellion - Merc 9.8
                              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                              What’s behind you doesn’t matter.Enzo Ferrari

                              Comment

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