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Technical 1956 Pontiac Looking for ideas for swaping/ rodding a 389 or 370 into it

Discussion in 'Traditional Hot Rods' started by oldschoolhemi, Nov 7, 2019.

  1. oldschoolhemi
    Joined: May 25, 2012
    Posts: 13

    from Boring

    Hey troop! Ive got a 1956 Pontiac Star Chief 2-door hardtop with a dead 316, wanting to build/swap my 1959 389 out of my Bonne and use either the 56 Hydramatic or 59 Hydramatic. looking for Ideas on stuff. Thought about punching it to a 400, Ive read my 59 motor will take it if sonic tested, but?..
    Also have a 58 370 tripower motor stashed, but thinking the 389 would give the best bang for the buck. The 370 is kind of an orphan anymore.
    I see Butler performance has nice mods for 389's but they say my crank trans pilot hole will be an issue. Been doing some home work on the Safari site, they say what fits, but not much on horsepower upgrades internally. A good cam suggestion would help. Ive read my engine design is limited to pre-1961 automatics. Cant shift much anymore, getting to old and broken, so I want to stay with an automatic. Any ideas, help appreciated. Links to previous topic discussions would help , too.
    Im in need of a 57 Poncho or Olds rearend, also, if available in Oregon or Washington.
    31hotrodguy and Rusty Heaps like this.
  2. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,446


    "I heard".....Pontiacs are different from SBC as far as camshafts and cam timing. What works for a SBC don't for a Poncho. You prolly know this already since you have dealt with a bunch of 'em.
    I wonder.....boring to the max (389) IF the wise thang to do. For sure you won't be boring it again. When you think about that will the power increase be REALLY that great? I have ridden/drove/seen some real healthy GTO in the past. (389). It will take that 56 for a REAL ride once its built. Jus say'in!
  3. Through the years I've owned 11, 55-57 Pontiacs. All the 55s and 56s have had the old slant-pan dual coupling 4 speed hydro and I've put 1959-60, 389s in some of them. I have no idea what you need to do to put a 389 in front of the later style but the rest of the swap is straight forward. Front motor mount from the 56 will work on the 59-60 engines. If you keep the 56 trans you can keep your original rear motor mounts. The 56 exhaust manifolds will bolt up but they have little ports and the center one is "Siamesed"...both center exhaust ports in the head go into the same hole in the manifold.
    You can use your same intake on the 389 if you want or use the 389s. Generator mount is the same on the 59 intake...can't remember if the 60 motor is the same.
    59 was the last year for reverse cooling with the coolant elbows going into the front of the heads but if you keep all the '60 front cover stuff on the 60 motor you'll have no problems using it in your car. Maybe someone else will chime in regarding the 56 jetaway or strato jet of whatever they call that inferior trans in the 56 Star Chiefs. Not a fan of those transmissions at all.
    BTW, the 370 is a great 2nd choice for you. In 1958 Pontiac held a class record in drag racing with the 370 for many years...I'm running one in my 34 ford [avatar] with a muncie 4 speed behind it. I'm happy with it.
  4. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,241


    They are all orphans now.

    All the info you need.

    Post 1960 guys aren't interested in the 59 but pre 1960 guys all look for the 1959 389 so don't screw it up. For what you want the 370 or 389 will work. They are basically the same engine for your purpose. Your issue as it is for everyone wanting to upgrade is exhaust. Putting a lot of money into the engine and you are still stuck with the factory exhaust manifolds or make your own headers and you don't have much room around the steering box.
    Old wolf and kidcampbell71 like this.

  5. Yes the 389 should fit Ok. improve the exhaust. If your 389 is in good cond don't work on it. If its not broken don't fix it. you can use the 370 tri power on the 389. the later HEI dist and aluminum oil filter adapter are good upgrades. the oil filter adapter allows use of a much smaller sipn on filter and gives room for exhaust upgrades. Get Jim Hands Book. His son is on the HAMB.59 389,s had steel rods that stretched under continued hard running. Nicknamed Rubber Rods. You 370 and mybe your 389 has holes drilled on the outside of the head to the valve guides to prevent oil from being vacuumed past the valve guides and out the exhaust. be certain that they are not clogged. if they aren't clear it will appear like it needs piston rings. esacially like after coasting down a long grade or any high vacuum condition. Install a PCV to help keep the insides of the engine cleaner.
  6. Rusty Heaps
    Joined: May 19, 2011
    Posts: 757

    Rusty Heaps

    Apparently we are not too far off in our projects, your '56 and my '55. I'm trying to put a '74 model 400 in mine. Still up in the air on transmission. Not sure what will bolt to it, I'm more familiar with Chevrolets.
  7. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695


    Actually, the Slant Pan is a single coupling unit, although BOTH the Slant Pan, and the "new" design dual coupling Hydramatics were available in 56 Pontiacs. Who knows why they did that? I am Butch/56sedandelivery.
  8. ratrod40428
    Joined: May 19, 2004
    Posts: 195


    I have a 57 Olds/Pontiac read end housing, axles and 2 3rd members... but I’m in Santa Cruz, CA... message me if your interested and we can talk options

    Sent from my iPhone using The H.A.M.B. mobile app
  9. the only thing that will bolt in your car is a 55 thru 60 Pontiac V8 bolted to a pre 61 trans that has rear mounts on the bellhousing. As far as transmission that will fit your engine. any 65 or newer BOP trans that came from a engine that has a block mounted starter.
  10. Rusty Heaps
    Joined: May 19, 2011
    Posts: 757

    Rusty Heaps

    Let's see some pics!
  11. Bird man
    Joined: Dec 28, 2009
    Posts: 645

    Bird man
    from Milwaukee

    An 068 cam replacement would be a great cam. Not too crazy, plenty of grunt & affordable. The experts say to advance it 4 deg. The stock '57 cam is identical to the 066 Tri Power cam, just a different part# so that would be "stock".
  12. 55chieftain
    Joined: May 29, 2007
    Posts: 2,186


    I have a 57 Pontiac housing and Olds 31 spline axles and a 3.08 posi. But would have shipping from IL.

    Your situation depends on how good your trans is. A 59 389 can be bored quite a bit, and $ 300 more can a stroker crank and make a 453 and have gobs of tire roasting torque. Butler performance or Kauffman racing can sell a complete kit to do what ever you want.

    My 55 has a 74 455. I use a style.of Hurst mount that uses the side mounts of the block, not the front cover.
  13. Bird man
    Joined: Dec 28, 2009
    Posts: 645

    Bird man
    from Milwaukee

    No posts since the first, how 'bout it?
    Old wolf likes this.

    Nov 15, 2019"
    Looks like he more important things to do.

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