Are 307 and 350 heads interchangeable?

Discussion in 'Engine Topic' started by spaman71, Dec 9, 2008.

  1. I have been told my 307 heads will cost $850 to rebuild and with few around I am considering my options. Are 307 heads and 350 heads interchangeable. 350 heads are easyier and cheaper to find in Australia. My other option is to buy a 350..

    Thanks, Scott
     
  2. Kamikaze

    Kamikaze Veteran Member Lifetime Gold Member

    Yes and no.

    You have to be careful of a few details.

    The heads will physically bolt on but you have to watch for the valve sizes since the bore of the 307 is smaller.

    Also, depending on the 350 heads, you have to watch that the combustion chambers aren't larger than your 307's. If they are, you'll lose compression and the power output goes down.
     
  3. hhott71

    hhott71 Veteran Member Lifetime Gold Member

    14,377
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    Mar 30, 2001
    Joplin Mo. 64801
    307 heads are the bolt-hole accessory versions of 283 and 327 2 bbl heads with 1.72" valves.
    You can use 1.94" valve 350 heads on a 307 with zero problems, but you will need the 64cc chambers and flat top pistons to keep any compression.

    Your very BEST bet is a pair of 305 heads, the HP 305 or Vortec 305 heads with 1.84" valves, and really decent ports and small chambers will really put a boost of power and at a lower price!
     
  4. Damon

    Damon Veteran Member

    12,937
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    Nov 16, 2000
    Philly area
    I woudn't spend any money on a 307. Definitely not if the bottom end needs work.

    If you just need a set of heads to get it running grab a set of heads off a later 305 and bolt them on. If you can find a set from the early/mid 80s with the bigger 1.84 intake valve you've now upgraded from your stock 307 heads for very few bucks. They'll raise compression a bit (58cc chambers) and flow a little better than the 307 castings. I wouldn't go any further than that before you consider stepping up to a 350.
     
  5. 1981coupe400ci

    1981coupe400ci Veteran Member

    6,911
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    Dec 22, 2002
    Oregon,IL
    think of a 307 as a stroked 283...

    since it really is...

    283 bore block 327 stroke crank

    a H.O 305 head would be a good add on... or maybe a 350 vortec head.

    i had a 307 with a crane 272 cam and holley intake...

    ran great.
     
  6. pdq67

    pdq67 BANNED

    10,496
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    Jul 26, 2001
    Columbia, MO, USA
    Imho, hunt up a pair of 305HO, -601 heads and cc them so that you know what they are so that you can make DARN sure that your CR isn't too high!

    They range from 52 to I figure 58 cc's so CC THEM to know for sure!

    Try for right at 10 to 1 CR and that old 272/272 Energizer cam and also CC's 268HE along w/ a 300-36 Holley true high-rise and an old 600 cfm, 1850 carb and a set of cheap 1.625" dia., 4-tube, long headers uncorked will make her run like a "scalded-dog"!!!!

    pdq67

    PS., open up the chambers if too high a CR w/ either Fel-pro #1094's at .015" thick or stock type at .020" thick shim headgaskets to hold your quench tight!!!

    AND GO!!!!!!!
     
    Last edited: Dec 13, 2008
  7. -=79z28=-

    -=79z28=- Veteran Member Lifetime Gold Member

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    Charlotte, NC
    this is pdq's 27th time he has said this exact post in a thread about 305 heads...LOL

    Good info though for sure, power on a bugdet.
     
  8. pdq67

    pdq67 BANNED

    10,496
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    Jul 26, 2001
    Columbia, MO, USA
    Dam-it Guy's!! I really try ta help is all!!

    And I'm "shade-tree" as all git-out and and I am a cheap SOB to boot!

    pdq67
     
  9. -=79z28=-

    -=79z28=- Veteran Member Lifetime Gold Member

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    Jan 22, 2008
    Charlotte, NC
    i was just kiddin dude, you definitely have some of the best info on this site.
     
  10. pdq67

    pdq67 BANNED

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    Jul 26, 2001
    Columbia, MO, USA
    Thanks -=79 for the back up.

    My Buddy Mark, (mbrekke), over at Team Camaro has a mildly hopped up 68 1st Gen. Camaro 210hp/327 that is pushing over 400 hp and you talk about run! He, He!! Like a "scalded-dog"!!!

    Cam is an old-school Isky Z-25!! Along w/ an rpm and I wanna say a 600(?), may be off here?, low dollar, big valve, aftermarket cast-iron heads from Summit that make like somewhere around 10.25 to 1 CR and headers is all.

    pdq67
     
    Last edited: Dec 11, 2008

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