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Technical 327 : Large vs Small Journal

Discussion in 'The Hokey Ass Message Board' started by Wyld Deuce, Feb 18, 2017.

  1. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,304

    henryj1951
    Member
    from USA

    We made 377ci's few years back ---1971/72---by turning the crank offset ... something to do with 9/16th's...
    oh ya 3 9/16's....
     
  2. Dezul
    Joined: Sep 4, 2021
    Posts: 2

    Dezul

    If someone would help me with this I would appreciate it. He has two short blocks or 67 small Journal and a 69 large Journal. I'm thinking since I'm not going to be using this for Speed the large Journal should do me fine since it's $250 cheaper can I get a feedback please thanks
     
    1Nimrod likes this.
  3. Dave G in Gansevoort
    Joined: Mar 28, 2019
    Posts: 798

    Dave G in Gansevoort
    Member
    from Upstate NY

    First question: do you plan on having it rebuilt before you use it? If so the large journal 327 may be easier on your wallet as things like bearings, rods if needed, and even items like rod and main cap bolts are the same as those used in 350 engines.

    Second question: is the El Camino going to be just a boulevard cruiser? If that's the case you may want to get a 350. They are plentiful still compared to the 327s, and with the longer stroke (3.48 vs. 3.25 inch) they make better power in the lower rpm range, ideal for a street machine that is on the heavy side.

    Third question: are you working to a budget number? If yes you may be better off getting a GM 350/290hp crate engine. I believe they even come with some sort of warranty for street use. Current cost in the low $3000 bracket.

    If you really like the idea of going 327, either one would make a decent street engine, with all the caveats mentioned in the thread.

    Good luck and keep on trucking, as we would have said way back when...
     
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  4. Ericnova72
    Joined: May 1, 2007
    Posts: 475

    Ericnova72
    Member

    As long as it has no issues internally that the seller isn't disclosing like spun bearings or flat camshaft/bad lifters, the large journal will do everything you want it to do..
     
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  5. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,651

    1934coupe
    Member

    Dezul where are you located?

    Pat
     
  6. olscrounger
    Joined: Feb 23, 2008
    Posts: 4,368

    olscrounger
    ALLIANCE MEMBER

    small journal for me--have had many-currently have two. My favorite engine.
     
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  7. firemangordy
    Joined: Feb 28, 2007
    Posts: 377

    firemangordy
    Member

    Small journal blocks have the hole in the back for the PCV system so you can run early valve covers without having to punch holes in them to vent the crankcase.

    Gordy
     
  8. X-cpe
    Joined: Mar 9, 2018
    Posts: 1,247

    X-cpe

    307 crank + 350 block = large journal 327
     
    1Nimrod, Deuces and 47chevycoupe like this.
  9. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,330

    sunbeam
    Member

    I have never seen a small journal 327 crank that were cast there are rumors of late 67 210 hp 327s having cast cranks. In 67 I had a 283 come in for a rebuild with a knocking noise it had a cast crank that was broken between the #1 rod journal and the front main. There are both cast and forged big journal 3.25 cranks. I used a forged one in the last 348 small block I built.
     
    Last edited: Sep 5, 2021
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  10. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,651

    1934coupe
    Member

    62 thru 67 where all SJ

    I believe all 307's are cast iron cranks.

    Pat
     
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  11. Deuces
    Joined: Nov 3, 2009
    Posts: 21,294

    Deuces
    Member
    from Michigan

    If you plan on using a 307 crank in a 350 block, make sure you have that crank re-balanced!!!!!..... It's not the same as a 327 crank other than the stroke....
     
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  12. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,330

    sunbeam
    Member

    I didn't proof read my statement I corrected it. When Chevy increased the stroke 1/4 " with less journal overlap my guess is they thought a cast crank would not stand up.
     
    Last edited: Sep 5, 2021
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  13. dana barlow
    Joined: May 30, 2006
    Posts: 4,485

    dana barlow
    Member
    from Miami Fla.
    1. Y-blocks

    I used up 2 steel forged big J,327 cranks over two years of racing{then could not fine more at my $$s,being very low $ racer in a super high $ class filled with drugrunners with unlimited $* in south Florida in the 1979 to1981}. Loved them cranks for what I was doing with my Late model Mod. oval track racer. The class rules made it best to have 350 Cu/In,so super hotdogs were buying around $60,000*engines like cord wood.
    I designed n built, plus drove my own, I used a 400 SBC block with spacer mains*>giant oil cooler*<also home made ,an 327 big J forged crank with pink polished 350 rods ,on flat-top pistons,an Brownfeild alum heads.= So longer rod then 400,shorter stroke an = 348 in. stock bore of 400 block< Engine was bad ass at jumping off corner better then super $$$ druggy engines,an my own trick engine was added a lot by a self designed an built total **very custom alum. PowerGlide tranny.< used no torque at all.
    My design tranny shifted with ZERO**** time from low to high*****{ don't shift in the turn........................Was the only autotranny that held up on blacktop..... My design was not like TCI that also had a dirt track auto tranny,but if TCI used on blacktop blow up!Burned out both band an clutchs.
     

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    Last edited: Sep 6, 2021
  14. Budget36
    Joined: Nov 29, 2014
    Posts: 7,236

    Budget36
    Member

    What is a G crank? I’m sure when you tell me I’ll have an “ah ha” moment:)
     
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  15. dana barlow
    Joined: May 30, 2006
    Posts: 4,485

    dana barlow
    Member
    from Miami Fla.
    1. Y-blocks

    Thanks,I needed to proof read an fix spelling,the g was to be a "J",yup,78 YO eyes an fingers are sloopy now ! LOL
     
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  16. Budget36
    Joined: Nov 29, 2014
    Posts: 7,236

    Budget36
    Member

    I was thinking that;)
     
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  17. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,330

    sunbeam
    Member

    The first 348 SB I built used modified 300 ford rods later ones used speedmaster PCE 274--1036 rods 6.25 long and off the shelf 400 6.00 rod pistons. I follow Smokes rule when ask how long of rod do you run answer the longest one that will fit. They make great street engines. They seem to be less octane sensitive
     
    Last edited: Sep 5, 2021
    1Nimrod, dana barlow and Deuces like this.

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