Milling a 302 head

Small Block Mopar Engine

  1. glhx

    glhx Well-Known Member

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    what is the max I want to mill off of this head? I’ve seen anywhere between .030 and .050

    What are the drawbacks of going that much?
     
  2. Slantsix64

    Slantsix64 Well-Known Member

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    i milled .045 off my 302 reduced them from 64CC to 58CC but measure how far your pistons are in the hole, the later LA Roller motors have flat tops that way closer to the deck that the later 1971-1985 318s got you measure everything i got to 9:5 CR using 302 heads and thin head gaskets
     
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    • glhx

      glhx Well-Known Member

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      Running a 76 318 and using the thinnest mr gasket head gaskets I could find. I haven’t checked how far down the hole it is but I know it’s pretty far. Probably .060 or more

      I also thought about putting them in a 69 318. Higher compression but the pistons have the valve reliefs. Decided not to run this one because the cam is only a 262.

      Did you have to shave the intake side and use new push rods?

      Did it affect the distributor gear mesh?

      Any problems with water jackets or warping?
       
      Last edited: Dec 29, 2019
    • Slantsix64

      Slantsix64 Well-Known Member

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      nope no problems .045 is the max, honestly i would check how far that piston is cause if its too deep like the 1971 318 i had you will if lucky hit 8.1 or 8.2, early 318 had them closer to deck height
       
    • glhx

      glhx Well-Known Member

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      Even with the earlier model 318. I wonder if I shave that much off the head. Will the 262 cam hit those pistons.

      I think that 69 had 9:1 factory. The 76.....no idea yet as it’s torn down right now.. It can’t be any worse than the smog heads and that low compression except that I lost the metal head gaskets when I tore it down. I was surprised it still had them.

      Did you take any off the intake side to get that much off the block side?
       
    • BigBlockMopar

      BigBlockMopar BigBlockMember

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      '70s 318 smog-engines have a 8.6:1 adv. static compression ratio.
      I milled a pair of 302s down to 60/61cc and slapped them on a zero-deck 360 netting a 11.3:1cr with a thin headgasket.
       
    • WayneShelton

      WayneShelton Well-Known Member

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      My first thought was isnt a 302 a Ford or Chevy, and nothing to do with a Mopar.
       
      Last edited: Dec 30, 2019
    • glhx

      glhx Well-Known Member

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      I’d like to end up with around 9:1

      Im on the fence on these two engines. I am thinking of milling the heads for the 76 block

      Or just throwing them on the 69 block without milling.
       
    • glhx

      glhx Well-Known Member

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      No.....the 302 is a set of factory upgrade heads. The 302 is the last 3 numbers in the casting. They have swirl ports and heart shaped chambers. I pulled them off of an 87 van. A nice upgrade for a low performance engine
       
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      • WayneShelton

        WayneShelton Well-Known Member

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        Thanks.. didnt know that. Other then the Ford/Chevy 302's lol. Learn something every day..
        Was trying to figure out why you were asking about Ford/Chevy motors on this website. LOL
         
      • Slantsix64

        Slantsix64 Well-Known Member

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        i would go with the 69 block and measure the piston height just cause it said the early 318 had 9:1 in reality probably had 8:7 or something like that, my 1971 318 was suppose to have 8:6:1 but in stock form really head 7:9:1 so measure how far in the hole, head gasket size the 302 heads are 64cc then you can calculate hot much to mill off to get to where you want, i think early 68-69 318 are .30-.40 and my roller 318 was .20 in the hole
         
      • Slantsix64

        Slantsix64 Well-Known Member

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        Also advancing the camshaft will help build up PSI in the cylinders i had 125 Psi adavanced it four degrees and got 150psi in all cylinders if your looking for that low end grunt
         
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