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Deck Height ?

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  • Deck Height ?


  • #2
    In the April TW Cooperator Jim Pepper states most 259 engines had a design flaw in that they had about a .060 deck height. The article suggests milling the block. It does not state what the target deck height should be.

    Frank van Doorn
    1962 GT Hawk 4 speed
    1963 Daytona Conv
    1941 Champion R-2 Rod
    Frank van Doorn
    Omaha, Ne.
    1962 GT Hawk 289 4 speed
    1941 Champion streetrod, R-2 Powered, GM 200-4R trans.
    1952 V-8 232 Commander State "Starliner" hardtop OD

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    • #3
      quote:Originally posted by SuperHawk

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      • #4
        quote:Originally posted by Chicken Hawk

        quote:Originally posted by SuperHawk
        Figures I've seen says the 259 deck is .082". I'm guessing the factory did this so the compression would be the same for both the 259 and 289 with the same heads, but I'm only guessing on this.

        The 289 is supposedly .031" and the R engine .019". Most 289's I've checked come in around .025"

        Ted Harbit
        sigpic
        Lark Parker --Just an innocent possum strolling down life's highway.

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        • #5
          On 3 late model engines, an R1 and 2 289's, the deck heights were all in the similar range, and variable from .033 to .018", with the R1 the most variable. As I recall, without checking my numbers, the right bank had the higher deck heights and tapered in all cases. The height was measured by confirming TDC on #1 with the dampener mark and degreeing the dampener for all other 6 measurements. The cross-bank pattern didn't suggest crank error. Has anyone else measured all bores of an "unmolested" factory block?

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          • #6
            I have measured the decks of a 59 Ford 292 v8 block and they were tilted inward and sloped to the front. I had that block decked by a shop with a Rottler F65 CNC machining center and it squared the decks to the crank and leveled the block.

            I'll be checking/decking a 224 block later this year if things go well.

            Best regards,

            Paul
            Best regards,

            Paul

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            • #7
              Well Larry; just remember, you can only remove the amount of material from the top of the block, that is equal to the amount of "drop" of the Intake vs. the excess in the port wall width of the upper and lower surfaces of the Intake Manifold ports! [:0]


              StudeRich at Studebakers Northwest -Ferndale,WA
              StudeRich
              Second Generation Stude Driver,
              Proud '54 Starliner Owner

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              • #8
                Larry -

                An answer to your question is...it depends!

                1. desired TRUE compression ratio
                2. the head gasket you will use

                Most "advertized" ratios aren't correct. You must measure the head chamber cc's, the gasket cc's, and the cc's as measured with the piston at TDC. Run thru the numbers and see what you have.

                Milling the deck is one way to go...but remember, the farther you mill the deck, the farther off the intake manifold will be at the port opening and the hold down holes.

                Mine...I had the deck milled to achieve a zero deck. That is, the block deck and the piston top is the same. Actually, my pistons are .004" down in the hole. This is to keep the piston as close to the head as possible at TDC. This helps the combustion process.

                As I noted...I'd have your shop calculate the "true compression" ratio and go from there.
                A good number to shoot for is 9.00 to 1. That should give reasonable performance while it should also make it able to use mid grade gas.

                Mike

                Mike

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                • #9
                  Mike mentioned the combustion process. The effect you are seeking is 'quench' or 'squish'. It's both, actually; quenching the flame front to prevent detonation, and squishing the combustion gasses out of that area so that they burn.

                  The flame of the combustion does not burn any closer to the walls of the combustion chamber than .060" (quench). If an area of about .080" or more is left in the combustion chamber, trapped gasses that won't burn will tend to detonate when the combustion pressure rises high enough. If you arrange the piston and head so that the distance between them is closer to .040" that detonation is avoided. As an added benefit the gasses get squirted out into the combustion chamber where they can burn and where they add to the turbulence of the flame.

                  You've got some calculating to do. Thick head gaskets vs. thin (shim) head gaskets, and how much to deck. Since you are milling the block, you have the opportunity to use the thin head gasket. The thin head gaskets seal better when the surface is flat and has the right texture. Are your heads getting shaved? Are your pistons dished or flat-top?

                  If I recall correctly, the thin head gaskets are about .017" thick. That would mean that you want the piston to be down in the hole .020 to .025" to get .037-.042" of deck clearance.

                  Best regards,

                  Paul
                  Best regards,

                  Paul

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