1. Cuda65Steve

    Cuda65Steve Member

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    What's a reasonable shave on a 225 head? Looking for a slight bump in compression.
    Gonna have a 2bbl into stock exhaust manifold and a 2.5" flowmaster.
     
  2. moparmat2000

    moparmat2000 FABO Gold Member FABO Gold Member

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    According to mopar performance you can go up to .110" no joke. I would shorten the head bolts with that so they dont bottom out before you hit proper torque and gasket squeeze.
     
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    • RustyRatRod

      RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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      I just had a 170 head milled .100. Took it without lookin back. I think @Charrlie_S has "accidentally" done one like .125". lol
       
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      • Charrlie_S

        Charrlie_S Well-Known Member

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        You really need to determine the use of the vehicle, and what octane fuel you can live with. Decide what CR will get you there, then make measurements to determine how much to mill. You can't run 9.5 CR, with a stock cam, and stock dist curve, on 87 octane.
        Not a major issue on the 198/225, but should ALWAYS check piston to valve clearance on a 170.
        There are some builders who have milled he block .100 and angle milled the head .100 on one side, and .200 on the other side. Not for the faint of heart.
         
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        • Charrlie_S

          Charrlie_S Well-Known Member

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          Not necessary to shorten the bolts. Clean the threads in the block, and use lubricated hardened washers, under the head of the bolt. Thread engagement will be close to the same, and will have better clamping force.
           
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          • moparmat2000

            moparmat2000 FABO Gold Member FABO Gold Member

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            I beg to differ. I had a 69 dart with a 225. Bought this thing with a badly warped head. It took .100" to make it flat. I chased out all the threads in the block and blew em out with compressed air, cleaned the bolt threads on a wire wheel on a bench grinder. Then on installation, i installed the bolts with a small amount of oil on the threads to effect a proper torque. This engine popped 2 head gaskets in a short period of time after that. Ended up having a machine shop buddy of mine knock 1/8" off the ends of the bolts before I installed head gasket #3.

            After that, I had no head gasket problems. What was happening was The bolts were bottoming out and providing barely enough clamping force, and the gasket would be fine for a very short period of time, then it would pop. Maybe my block was not drilled and tapped deep enough from the factory, but removing a bit from the threaded end of all the head bolts seemed to correct the issue with as much as I had to have milled off the head. BTW that .100" milled seemed to give her a little more getup and go as much as one can get from a stock 1 barrel slant sux.
             
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            • Charrlie_S

              Charrlie_S Well-Known Member

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              That is why you use the washers. They are close to the same thickness, as the metal shaved from the head. So the thread engagement stays the same.
               
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              • moparmat2000

                moparmat2000 FABO Gold Member FABO Gold Member

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                I used whatever was there. Add washer, or shorten bolt threaded end by a small amount, still the same difference. End result was still the same. It quit popping headgaskets.
                 
                Last edited: May 29, 2020
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                • Cuda65Steve

                  Cuda65Steve Member

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                  You've got nitros and turbo Slants...….None have a shaved head???
                   
                • Charrlie_S

                  Charrlie_S Well-Known Member

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                  NA 170 street motor has 9.5 CR (which is too high for the cam I am running. Had to do a lot of distributor work).
                  170 turbo motor has head with just a "cleanup/truing" cut and a .080 thick head gasket (7.9 CR)
                  Nitrous 170 and 225 motors both have approx .125 milled off the head (38cc chambers)
                   
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                  • Killer6

                    Killer6 Well-Known Member

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                    That is sorta/kinda true, but besides not having to "machine" the end off by a pro, or grinding on ones own & cleaning up the threads, a set of lubed & hardened washers results in better/more even torque on the bolts w/o all the grinding....................
                     
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                    • moparmat2000

                      moparmat2000 FABO Gold Member FABO Gold Member

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                      Very true, but at the time I was fixing this thing, and was solution i came up with.
                       
                    • Killer6

                      Killer6 Well-Known Member

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                      Gotcha, been there........in 40+ years of working on stuff, I've gotten it done,...& later said"why didn't I just?" after the fact. A lot more in the early days for sure, lol!
                       
                    • moparmat2000

                      moparmat2000 FABO Gold Member FABO Gold Member

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                      It's called "sperience". Back then I had less of it. I was in my mid 20s and just needed it to work. If I had that issue now, I woulda just grabbed some 2.2 headbolt washers out of my stash. Heck what am I talking about here (scratching my head at that absurd thought). Actually I woulda just jerked the whole thing out pegleg rear axle, front drums and all. Woulda dumped it all in my scrap trailer, and installed a magnum 360 / 46RH combo out of a ram van or pickup. Along with a ford explorer 8.8 to round it out, and with M body disc brakes in the front and never looked back
                       
                    • Killer6

                      Killer6 Well-Known Member

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                      Now now!! :poke:
                      None of that!!^^^
                       
                    • Slantsix64

                      Slantsix64 Well-Known Member

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                      If its all stock mill .100, and have your dizzy recurved as well,you can reuse stock push rods.
                       
                    • Charrlie_S

                      Charrlie_S Well-Known Member

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                      And what CR will that be?
                       
                    • Slantsix64

                      Slantsix64 Well-Known Member

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                      ;;
                      Depending on year on 225 piston height and gasket 9:1 to 9:5. My stock 78 225 had pistons .170 in the hole cut my slant head .100 to .45cc heads that motor barely got to 9:18:1 But that had me at a cranking psi of (155-160) from a weak 120psi previously my other slant six 1966 block had the pistons closer up .120 in the hole got me in the 9:4:1 range after everything was calculated, its not rocket science although a 170 engine has the piston height higher almost flush to the deck so i would watch out for that .100 cut will get you close to 10:1 on a 170.
                       
                      Last edited: Jun 3, 2020
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                      • Charrlie_S

                        Charrlie_S Well-Known Member

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                        That is exactly my point. Unless you measure, you don't know for sure. There is a large difference in tuning, and octane requirement between 9 to 1 and 9.5 to 1
                        Also the cam makes a big difference in what CR will work. My 170 street driver is a "true" 9.5 to 1, with the mildest Mopar performance cam. It likes 93 octane. I was able to use 89 octane, with a lot of distributer work. Would have been better with 9 to 1, or a bigger cam.
                         
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