Putting 340 intake on 273 heads??

Early A-Body Discussions

  1. hellfish

    hellfish Member

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    I have a 340 small bock currently being rebuilt and wanting to use 273 heads due to there're closed chamber heads, will a 340 intake bolt up to the 273 heads?? Or does anyone have any suggestions.
     
  2. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

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    64 and 65 heads not without modification to the intake. 66 and up heads yes it will bolt up but there will be a big mis-match in the ports. The 340 ports are large compared to the 273 ports. You could port match the intake to the heads but I am not certain that there's enough meat in the ports. I wouldn't recommend using them. tmm
     
  3. oldkimmer

    oldkimmer FABO Gold Member FABO Gold Member

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    ...............Like TTM says about the mismatch..............go ahead and use it, many do....including me.....there is lots of aluminum intakes out there........kim...............
     
  4. hellfish

    hellfish Member

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    Thanks TTM & Kim!!!!
     
  5. hellfish

    hellfish Member

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    Would you have to drill the bolt hole angle on the intake to match the 273 bolt holes??
     
  6. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

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    Only if the heads are 64 or 65's
     
  7. hellfish

    hellfish Member

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    Thanks TTM, mine is a 65, I gues I got my work cut out for me. All of this is due to 340 block being done and needing the 273 closed chamber heads for higher compression.
     
  8. oldkimmer

    oldkimmer FABO Gold Member FABO Gold Member

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    ................u can do a set of the 85-91 302 heads and be wat farther ahead.............kim.........
     
  9. Bad Sport

    Bad Sport HALF A BUBBLE OFF Staff Member FABO Gold Member

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    x2
     
  10. 65Val

    65Val Average Length Member

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    Yes, but you still have the small ports.

    Why not just cut the block and the heads enough to reduce the 340 head chambers to 273 size?

    --or--

    Get higher squeeze 340 pistons, since you have the block at the machine shop anyway....?
     
  11. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    What pistons are in the 340?

    The earlier 340's have pistons that are proud of the deck. The '68 I built with KB 243's has the piston's .018" over the deck, no need for closed chambers to get compression. In fact, it's not hard to run into piston/valve clearance issues.

    Even on the later 340's, if the pistons aren't buried in the block you shouldn't have a problem making compression with 340/360 open chambers, should only need a small cut on the heads. Otherwise you're going to have a big mismatch on the ports.
     
  12. ValiantRacing

    ValiantRacing Well-Known Member

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    You will kill that 340 with 273 heads on it, just put on some 360 heads and then no problems with intake or anything else.
     
  13. BillGrissom

    BillGrissom Well-Known Member

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    I thought I read that later 273 heads (66+) had less compression, so research that. There are alum intakes for the 64-65 heads, but rare now. I put an Edelbrock Performer on my 273 heads by counter-sinking the holes for a conical flat-head bolts which can cock to fit. Not ideal, but seems to work. Biggest concern is that the bolts have a small allen socket which could strip and require drilling the bolt heads off to remove the intake.
     
  14. 65Val

    65Val Average Length Member

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    '68 273 went to open chambers, and hydraulic lifters and non adjust rockers,....same heads as the 318LA that year and '69. 273 disappeared after 1969 model year.
     
  15. 340duster340

    340duster340 Well-Known Member

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    agree with above posts, and i would NOT put the 273 heads on the 340.
     
  16. 65cudalover

    65cudalover Well-Known Member

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    Just to double above posts, agree going backwards! 273 heads are old wood compared to more modern 340, 360 motor parts!
     
  17. Moparhead64

    Moparhead64 Well-Known Member

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    I have '74 360 heads with 2.02 intake valves and a holley strip dominator intake on my 340 and run the 110 racing purple gas because of compression ..... piston is at the top of the block ( 0 deck) with a 4 speed and 3:91 sure grip rear the aspalt crayons are getting thin ! DON'T DO THE 273 HEADS ! Only a suggestion !
     
  18. hellfish

    hellfish Member

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    Thanks Moparhead, decided to go with the 340 heads, having them shaved. I should get the engine back tomorrow or Friday. Will let everyone know how it goes.
     
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