Looking to upgrading from the 300 (4.9L) and the ST300

Discussion in 'Wrenchin' Secrets' started by Double6skylark, Aug 7, 2017.

  1. Double6skylark

    Double6skylark Well-Known Member

    Just bought a 66 Skylark back in June of this year which was sitting in a barn for the last 24 years.

    It wasn't running and and the manual brakes (4 wheel drums) were all shot as well.

    I put in a new fuel cell (because the old tank was rotten), fuel lines, fuel pump, and rebuilt the Rochester 2GC w/electric choke. Installed all new ignition: points, condensor, rotor, dist cap, spark plug wires, plugs, coil, voltage regulator, including alternator & battery. Drained & changed the oil and she fired up right away. To my surprise she runs great and doesn't smoke (or knock).

    I've upgraded the brakes to a dual reservoir power master cylinder with rotors & calipers for the front end and rebuilt the rears with new drums, cylinders, shoes & hardware so she can stop now. Also just installed brand new Flowmaster dual exhaust.

    The bad news....after driving her (short drives) for the last week I changed the oil again and now I hear a "rod knock" sound coming from the motor (where it never made it before since starting her up).

    Needless to say I've already invested a good chunk of change to get it this far and was looking to have a "somewhat" reliable daily driver....

    Anticipating worst case and because the 300 is a little rare and costly for a rebuild I'm thinking of swapping it out for something with better performance.

    Anyone gone through this or have any suggestions or insight on a cost effective performance engine/transmission swap option?

    Thanks in advance, any help is appreciated.
  2. 64 skylark mike

    64 skylark mike Well-Known Member

    Not sure on '66 cars, but the Buick 350 and TH350 fit right in my '64 Skylark. Motor mount and transmission mount location matched, and the drive shaft length fits as well. 350 is a little wider than a 300, but length is the same. A little heavier than a '64 300 partly because of '64s have aluminum heads and intake. But the '66 300 may be closer in weight to 350's since both are all iron.
  3. hugger

    hugger Well-Known Member

    Rockauto has replacement fuel tanks for cheap,...

    Your biggest bang for the buck will be a laremodel 5.3 engine/trans with a swap harness and the mount kit

    $4k would get it done

    Rebuilt 300 would run around $2k and still be slow and have the 2speed trans
    Do a th350 trans for better performance and you can add $500

    Used 455 swap if you can find a good one, $2500

    ReBuilt 455 swap $5500

    350/350 swap $1000 fair performance much better than the 300, with parts available to easily make 350/400 hp
  4. Gulfgears

    Gulfgears Gulfgears

    Check Craigslist often, there are 300's that come up for sale. That might be your cheapest bet.
    I have seen a complete engine transmission being taken out for an engine swap, and the 300 ran great.
    Just needed more HP.
  5. RivieraBud

    RivieraBud Member

    It all depends on what you're looking for in the end result. Initially, you said you were hoping to have a somewhat reliable daily driver, and where you've spent some money already for some parts for a 300, I agree with Gulfgears that looking for another 300 would be the cheapest and easiest swap. They are around, but you may have better luck scoring one in a parts car rather than looking for just the motor. Probably the next easiest swap would be to the 340 that was also offered in '66. That would give you a few extra cubes, and you wouldn't have to change the transmission if that seems to be working ok. I haven't tried the 350 swap suggested by Skylark Mike, but it sounds like that might be an easy swap as well. If you're thinking better performance in the way of big block performance, that's definitely not as straight forward. If you're thinking period correct big block, like a 401/425, most of those were in full size cars with mid-sump oil pans, front motor mounts, and different exhaust manifolds, so you would need to come up with one of the rear-sump oil pans, the cast iron block plates that convert the nailhead to a center motor mount configuration, and the necessary exhaust manifolds. If you were thinking 400/430/455, it can be done (I have a 455 in my '66), but it's not a direct bolt in, so those motors have their own set of challenges. If you're up to a bit more than a straight bolt in swap, you may want to consider something like a 3.8 turbo V6. They're about 20 years newer than the other options discussed, so you should have an easier time finding one. That would give you the increase in performance with daily driveability, and the bonus of pretty good fuel mileage. The first thing is to decide what the end result is that you're looking to achieve, coupled with deciding what kind of budget your willing to dedicate to the project. Once those parameters are set, there are plenty of us who are willing to help you with any questions you come up with along the way in putting it together.
  6. sean Buick 76

    sean Buick 76 Buick Nut Staff Member

    My vote is th350 and Buick 350

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