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How much can I Mill 245 head

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  • Engine: How much can I Mill 245 head

    Have a NOS 245 head. Plan fancy carburation, port matching and minimal intake smoothing. Stock cam. Hot ignition. Custom header. How much is safe to mill head. No decking planned.
    Greg
    http://salt2salt.com racing a 53' Stude on the salt.
    http://tribaker.wordpress.com building a 37' Stude boat-tailed speedster 3-wheeler
    http://turbostude.com building a 50' bullet-nose with a turbocharged stude flathead six (site under reconstruction)
    sigpic

  • #2
    It's safe to mill as much as .085".

    Just remember it's a tradeoff. Each increment of increased compression costs an equal increment of decreased transfer area intake and exhaust flow.

    Increasing the compression will increase low RPM torque, but the reduced breathing will cost horsepower at higher RPM. The racing Harley-Davidson KR flatheads seldom ran more than 6.5 compression, but they were turning 6,500 RPM. The Commander will never be a high RPM engine for any length of time.

    A turbocharger would be the way to make more power at sustainable RPM.

    jack vines
    Last edited by PackardV8; 04-15-2021, 04:36 PM.
    PackardV8

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    • #3
      Thanks Jack. Our Salt2Salt turbocharged flathead six used a KR combustion chamber design and ran 8.5:1.....then 20+ pounds boost. This engine won't be pushed very hard.
      Greg
      http://salt2salt.com racing a 53' Stude on the salt.
      http://tribaker.wordpress.com building a 37' Stude boat-tailed speedster 3-wheeler
      http://turbostude.com building a 50' bullet-nose with a turbocharged stude flathead six (site under reconstruction)
      sigpic

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      • #4
        You really do not want to mill head any more than necessary. You can increase comp to the point you can't start car without parking on a steep hill. Makes it real hard for starter to turn engine over. Won't improve performance enough so as you'd notice. You'll have a detonation problem with today's low octane white gas. Flow is limited by the most constricted part of induction and exh. You have stock cam and valves so I'm not sure you can expect too much boost in performance. Warren Rausch did some amazing things with a Champion 6 by re-designing the combustion chamber and flow. Too bad he didn't write it all down. (Don't spend too much money trying to make a silk purse out of a sow's ear. If you can just get a Commander 6 to start and run halfway decent, you're the man. If you want better performance, put an R1 or R3 cammed 289 in it; with a nice carb and unrestricted exhaust, you can get 240-250 HP and have a real reliable motor. (Sorry)

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        • #5
          Back in the 70's I ran a "big six" (245) in my 1957 Transtar. I found out it had a very profound hatred of high RPM. I peeled the tops off two pistons (with correctly gapped rings) if I ran it much over 4,000 RPM for even short periods of time. (Stock pistons) Balancing the engine during one of the rebuilds made no difference. It just would not tolerate high piston speeds. I eventually swapped in a 1960 259 and truck became a durable workhorse.

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          • #6
            Thanks guys. I was just looking to bring CR up from 7:1 to 8.5:1 to take advantage of modern gas. I will be running a knock sensor and J&S Safeguard like in the Salt car, at least for a while. Looking for torque, not rpm. Expect I will shave a "head gasket's" worth off the head. Been playing with turbocharged champion motors a long time, so I'm not just stumbling into this.
            Greg
            http://salt2salt.com racing a 53' Stude on the salt.
            http://tribaker.wordpress.com building a 37' Stude boat-tailed speedster 3-wheeler
            http://turbostude.com building a 50' bullet-nose with a turbocharged stude flathead six (site under reconstruction)
            sigpic

            Comment

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