What's the compression height for a 360 magnum as buying pistons

Discussion in 'Small Block Mopar Engine' started by maca, Dec 5, 2018.

  1. maca

    maca Well-Known Member

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    Hey all
    I want to buy a set of forged pistons for my 360 magnum. Does anyone know what compression height piston and I need or the factory height
    Bore 4"
    Stoke 3.58
    Rod 6.123
    Comp height?
     
  2. Max1196

    Max1196 Well-Known Member

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    Stock height 1.605"
     
  3. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    aftermarket flat tops are 1.667 plus or minus .001......
     
  4. Max1196

    Max1196 Well-Known Member

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    Yes, do watch out for some listings in the 1.675 range (For example Icon IC741), there could be a protrusion issue when used in a Magnum block with the 9.585 deck height as opposed to the LA deck height of 9.599"
     
  5. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    Dont think a stock block is going to be near those deck heights...and certainly not squared from the factory....

    if it stick out a few thousands....thicker head gasket cures that...
     
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    • maca

      maca Well-Known Member

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      Thanks guys I measured up a piston today and it looks like it's very close to the 1605
      I'm going to be running Boost so I want to try and keep my compression down so I'm going for a dish.
      Hoping to find a forged standard 4 inch dish piston that will suit my deck height. Dreams are free I guess
      My deck is only out .010 but i will probably have to square that up.
      Pistons are down the bore about .050 so if I add that to my 1605 I should be looking for a piston of a comp height of 1655 I reckon
       
    • maca

      maca Well-Known Member

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      Hey guys this has got me a bit confused.
      I've worked out I need a piston with a compression height of around 1.6 and the pistons with a compression height of around 1.4 are for strokers.
      so I went on to summit website and found these pistons with an installed high off just over 1.6 and a big dish which will bring my compassion down so they seem perfect. However when I look under the application tab it says that for a stroker build. But the stroker pistons are closer to 1.4 so not sure if it's a misprint or if the LA stroker pistons are different height to the magnum ones
       
    • 70aarcuda

      70aarcuda Master Hoader of SBM FABO Gold Member

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      how about posting a link to the pistons...cause other wise how can we see what you are looking at.......Good god oh mighty...LOL
       
    • maca

      maca Well-Known Member

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    • nm9stheham

      nm9stheham Well-Known Member

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      If you deck the block down .010" then these may stick out the top a tad. Not a killer problem but the installed height would be .005" below a 'nominal' Magnum block height before any decking.

      If you you deck the block to where these are right at deck height at TDC (zero-decked), then your Static CR will be right around 8.1 with a .040" thick head gasket. Looks like a decent choice of dish size for boosting.

      Don't worry over the 'stroker' item.... these compression heights are right. I'd worry more about the descriptive hype at the bottom, with the repeated use of the word 'extreme' LOL. I don't know a thing about this company, good, bad, or indifferent.
       
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      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        1/16 rings both
         
      • maca

        maca Well-Known Member

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        Thanks, that deck height is about what I worked out as well. My issue was also it's a brand I've never heard of and before. Its the only one I can find with that much dish. My head's are 62cc so my compression should be around 8.43 but I'm not sure to use a brand I've never heard of before
         
      • nm9stheham

        nm9stheham Well-Known Member

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        Ah OK, I used the wrong combustion chamber volume; your numbers are no doubt right. I now get 8.32 with .050" thick head gaskets.

        How much boost are you planning? And will this be ECU controlled fuel injection or carbed?

        No reason you cannot grind out some cc's from the chambers, and maybe use tulip-headed valves, all the get more volume. I've ground out 8 cc's from chambers before to set SCR with the desired pistons. (But not SBM's so I can't advise on where the thin spots may be).
         
      • maca

        maca Well-Known Member

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        Thanks for your reply, Your numbers are correct . I am using a .040 gasket but can go thicker. I've been running this engine for a couple of years on 15 PSI with a static compression of 9.3. I'm around 645hp at the wheels on the stock old pistons and one finally let go. It was a great setup but I thought while I'm going forged pistons I will try and drop the compression of it in case I want to go up to 20 psi. I wasn't sure if I could run 20 psi on 9.3 compression. these pistons would give me the compression I won't but I just wasn't sure about the stroker comment and the brand
         
      • nm9stheham

        nm9stheham Well-Known Member

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        LOL that is a lot for 9.3.....you must be running some race fuel. That is pretty amazing for the stock pistons. I have run 14-15 psi with around 8.2 SCR in a Mitsubishi 2.6L on pump premium and up to near 1.75 HP per ci, but that's at the flywheel, not the rear wheels. Good EFI helps.
         
      • maca

        maca Well-Known Member

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        Yeah I didn't think it would live for a couple of years but it did well. It's on E85 with a fitech injection carb.
         
      • nm9stheham

        nm9stheham Well-Known Member

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        E85...so why such LOW compression? LOL

        Does the FiTech have an option for a knock sensor?
         
      • maca

        maca Well-Known Member

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        No knock sensors on the fitech unfortunately. I was told you can't hear a knock on E85 and you need micro sensors to hear it.
        I'm going lower comp as I still got knock on E85 before I reach Max Power. The tuner said that my engine is knock limited and needs different pistons etc
         
      • nm9stheham

        nm9stheham Well-Known Member

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        I did not know that about E85 knocking...I wonder why a regular knock sensor could not detect it.