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  1. #1
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    Default 5.0 5.7 Vortec heads

    I have a 1996 5.7l Vortec engine I pulled from my Suburban 1500 with a spun bearing. Will the heads from this truck motor fit on my 1993 Mercruiser 5.0L motor to try to increase HP.

    I also wanted to thank everyone for all the help at the begining of summer. My boat ran great after all your help. I'm still only getting 28 mph and want more power for next year. Thanks, Mike

  2. #2
    Commander bifflefan's Avatar
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    Default Re: 5.0 5.7 Vortec heads

    They will probably fit, Im a Ford guy. But they are most likely exactly the same heads.

    If your only getting 28 MPH with a 5.0 you got other issues.
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    Lieutenant Commander Alpheus's Avatar
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    Default Re: 5.0 5.7 Vortec heads

    They will bolt right up to the block, but you need a new intake manifold to match the heads...


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  4. #4
    Supreme Mariner bruceb58's Avatar
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    Default Re: 5.0 5.7 Vortec heads

    Quote Originally Posted by bifflefan View Post
    If your only getting 28 MPH with a 5.0 you got other issues.
    His issue is that he has a big boat. 24' from what I saw in a previous post of his.
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  5. #5
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    Default Re: 5.0 5.7 Vortec heads

    Will the heads from this truck motor fit on my 1993 Mercruiser 5.0L motor to try to increase HP.
    Nope,... The valves are bigger/wider on a 350, because the cylinder bore is larger...
    The valves will/ might hit the edges of the cylinders...
    If they don't hit, they'll be shrouded, 'n not breathe properly....

    Basically, 350 heads won't go on a 305, 'n 305 heads don't work on a 350...
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  6. #6
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    Default Re: 5.0 5.7 Vortec heads

    Along with what Bondo said, 305 heads are usually 58cc where 5.7L vortecs are 64cc. That would lower the compression and reduce power as well.

    With a big boat, just rebuild that truck 5.7L and put it in with most of the marine parts from the 305.

  7. #7
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    Default Re: 5.0 5.7 Vortec heads

    So it sounds like the head swap won't work. My next step was to rebuild the 5.7 truck motor like Imported_John_S mentioned. Will I need to change the Cam? Also can someone recomend a performance Marine Intake for it?

  8. #8
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    Default Re: 5.0 5.7 Vortec heads

    The cam from the truck engine would work in the boat application as well. But wouldn't you want to replace the camshaft/lifters due to age, anyway?

  9. #9
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    Default Re: 5.0 5.7 Vortec heads

    Like I said the 350 Vortecs will bolt right on your 305 block. Been there, done that on my old Camaro.

    The problem was keeping the compression ratio close to stock.

    The stock compression is 9.3:1 using (305-5.0) 58cc heads.

    If you go up to(350-5.7) 64cc heads (Vortecs) then use Felpro embossed shim gaskets then you'll stay at 9.26:1 compression ratio. You just have to make sure the deck on the block is true, as well as the heads.

    Having said that, you will probably not want to run those type of head gaskets on a raw water cooled engine if you run in salt water. If you choose to use stock thickness head gaskets for marine use you will lower your compression ratio enough that the extra HP gain from the heads will become negligible. But they can and do bolt up...


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  10. #10
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    Default Re: 5.0 5.7 Vortec heads

    I'm for rebuilding the 5.7 and droppin her in...
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  11. #11
    Supreme Mariner bruceb58's Avatar
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    Default Re: 5.0 5.7 Vortec heads

    I believe they are the same. The part numbers for the heads between a 5.7 and 5.0 are the same in the Volvo and Mercruiser parts lists at least. Both 5.0 and 5.7 each have 2 part numbers listed and they are identical for each motor.
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  12. #12
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    Default Re: 5.0 5.7 Vortec heads

    Quote Originally Posted by bruceb58 View Post
    I believe they are the same. The part numbers for the heads between a 5.7 and 5.0 are the same in the Volvo and Mercruiser parts lists at least. Both 5.0 and 5.7 each have 2 part numbers listed and they are identical for each motor.
    The standard 305 heads were 58cc and had smaller valves. I believe they had recessed/dished pistons. I am wondering if the 305 vortecs, if they do use 350 heads, are they running a flat-top piston to match with the larger chamber?

    I still vote for the rebuild 350, though.

  13. #13

    Default Re: 5.0 5.7 Vortec heads

    The Votrec heads flow better and they will fit on the 305 but you will need to use a new intake manifold. I put the Vortec heads on a small block that was stroked, has 9.1 compression and then went with a marine cam to get the power I wanted to move a big heavy boat. Best thing I ever did, gets the boat on plane with only 1/2 throttle and don't have to use the trim tabs and it seems like a completely different boat. Went with more prop and gained a bit more speed as well with out the hassle of converting to a big block, it idles smooth and is good on fuel. I vote for rebuilding the 350, using the vortec heads, good cam and quality parts and you won't be sorry.

  14. #14
    Lieutenant Junior Grade spdracr39's Avatar
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    Default Re: 5.0 5.7 Vortec heads

    As has been said before " nothing replaces cubic inches". If you have big boat syndrome you need the bigger 5.7 anyway so why keep patching the 5.0?
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  15. #15
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    Default Re: 5.0 5.7 Vortec heads

    Quote Originally Posted by spdracr39 View Post
    ... If you have big boat syndrome you need the bigger 5.7 anyway so why keep patching the 5.0?
    Exactly.

  16. #16
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    Default Re: 5.0 5.7 Vortec heads

    you put a 350 head on 305 the intake runners are way bigger so you will lose air velosity [speed] combustion chamber way bigger you lose compresion engine will be dog.bore size on 350 4 inch 305 3 7\8 inch you will shroud valves all that work to lose all bottom end power go with 350 magic number for power is 4inch bore

  17. #17
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    Default Re: 5.0 5.7 Vortec heads

    intake runners are way bigger so you will lose air velosity [speed]
    Wrong!!!

    Do your homework and read the other posts. This has been asked and answered. As stated above the part numbers for the heads are the same...


    The part numbers for the heads between a 5.7 and 5.0 are the same in the Volvo and Mercruiser parts lists at least. Both 5.0 and 5.7 each have 2 part numbers listed and they are identical for each motor.


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  18. #18
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    Default Re: 5.0 5.7 Vortec heads

    Reread bondo's post. Other Chevy heads are different between 305/350 for this reason..valves hitting the cylinder walls. However, vortecs don't use real big valves from the get-go, so the same head MAY work on both, but you'll still have the shrouding issue.

    I've never understood why GM produces these 2 virtually identical engines. Only explanation..they can charge more $$$ for a 350..which is ALL profit.

  19. #19

    Default Re: 5.0 5.7 Vortec heads

    On your camshaft selection go with an RV cam, I assume your just going to use the carb set up. An RV cam will give you some good low end grunt and the top end will be decent as well.

    Also If your super ambitious, bore .30 over, will make it from a 350, to a 355 ish. That engine will really sing, and if all done right and not over carbed, you will easily throw off 275HP, as long as your lower unit is up to the task.

  20. #20
    Chief Petty Officer redjmp's Avatar
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    Default Re: 5.0 5.7 Vortec heads

    Quote Originally Posted by Alpheus View Post
    Wrong!!!

    Do your homework and read the other posts. This has been asked and answered. As stated above the part numbers for the heads are the same...
    10239906 12558060 12558062 are the "real" vortec heads that everyone wants. The '906 casting has a hardened exhaust seat that reduces flow so you might want to stay away from that one if you want pure performance but the hardened seat is preferred for regular marine applications.

    The 5.0L also came with vortec heads 12558059 but they are different totally than the "real" ones for a 5.7L. Similar but different. Combustion chamber is smaller and not heart shaped for starters, runners are slightly different as well.
    These are the heads you get from GM when you buy a 5.0L in a truck.
    And they are the correct size for a 5.0L, 58cc

    I am surprised that Mercruiser uses the 350 heads on the 305 as they are not the same.
    Gm marine engines use the 059 casting afaik.
    I sure hope so as I have a set ready to bolt onto my 898 along with a performance products manifold and edelbrock 4bbl.


    But I agree with the other people and recommend that you rebuild the 5.7L with the marine stuff from the 5.0L.
    Good for about 60 more hp.

    You will need to reprop and/or change gears in your upper unit though.

  21. #21
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    Default Re: 5.0 5.7 Vortec heads

    I'm going to start tearing down the 5.7. I'm also gonna go with the RV Cam and bore .30 over and would like to use a high performance Intake. Can someone recomend a Cam & Intake Package?

  22. #22
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    Default Re: 5.0 5.7 Vortec heads

    FWIW: Assuming roller cam, you can usually find the GM cam that is used in 350 Mercs for less than any aftermarket. You will not be able to go with much more lift than that, unless you also modify the heads. Being this is a heavy boat, wouldn't try to go for too much "high perf" stuff. Staying closer to stock, might be better. An Edelbrock Performer Vortec Intake should be fine. If raw water cooled and boat in salt or brackish water, will need bronze lined water passage or other treatment. If you are running a bravo drive, give more considereration to building a 383 stroker, than a hi perf 350.

  23. #23
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    Default Re: 5.0 5.7 Vortec heads

    The Boat is heavy. I think thats why the tired 5.0 can't keep up. The boat does have a closed cooling system. I'm also going to replace the cast manifolds and risers with a new set of Aluminum ones. I mostly boat in fresh water and hardly ever get to salt water.

    imported_John_S- I'm running an Alpha 1 gen 2 outdrive. Do you know how much horsepower it can handle?

  24. #24
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    Default Re: 5.0 5.7 Vortec heads

    Quote Originally Posted by Bond-o View Post
    Nope,... The valves are bigger/wider on a 350, because the cylinder bore is larger...
    The valves will/ might hit the edges of the cylinders...
    If they don't hit, they'll be shrouded, 'n not breathe properly....

    Basically, 350 heads won't go on a 305, 'n 305 heads don't work on a 350...

    Bingo...With that said they can be made to work.. But its a combination of pistons tops and cyl compresssion.. even the right gaskets.
    Stickly a opinion your milage may vary.

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  25. #25
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    Default Re: 5.0 5.7 Vortec heads

    Quote Originally Posted by pennyduke View Post
    ...
    imported_John_S- I'm running an Alpha 1 gen 2 outdrive. Do you know how much horsepower it can handle?
    300hp at the prop. More if you are careful. Torque help kills them too, but not from a 5.7.

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