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Technical 401 425 Buick Nailhead and ST400 Value

Discussion in 'The Hokey Ass Message Board' started by Basement Sweeper, Jun 9, 2020.

  1. Basement Sweeper
    Joined: Jan 24, 2020
    Posts: 81

    Basement Sweeper
    Member
    from Colorado

    A forum search didn't find anything recent. I'm looking for a 64 - 66 401 or 425 nailhead and an ST400 transmission for a future project, but I don't have any gauge of fair market value. I want to get a fair shake and also not offend a seller with a low-ball offer to where I lose an opportunity.

    I've located a complete (oil pan to intake, water pump to flexplate) 425 and ST400 w/converter combo out of a 1966 Riviera and will be meeting the owner soon to look at them and hopefully make a deal. It's a "best offer" deal, and we haven't discussed price. The owner knows nothing about the engine and transmission aside from that they turn over by hand and came out of his project car. He's unwilling to pull the oil pan or valve covers, so the best I'll be able to do is turn it over and peer through the intake runners, distributor hole, and breather holes. The speedo is missing from the car, so no estimated guess on the mileage. The chassis is already restored, so no guess on the mileage there either. From the photos, the engine and transmission are dressed stock with typical aged paint, dust, oil buildup but nothing that would suggest they are greasy unmaintained junkers.

    Questions for those in the know, preferably on Rocky Mountain region pricing:
    What is an unknown-condition complete 425 nailhead worth?
    What is an unknown-condition complete 401 nailhead worth?
    What is an unknown-condition complete ST400 w/converter worth?

    Thanks for the help.
     
  2. Basement Sweeper
    Joined: Jan 24, 2020
    Posts: 81

    Basement Sweeper
    Member
    from Colorado

  3. I'm assuming it has the starter, you should be able to rig it to spin the motor and do a compression test and maybe even check the oil pressure. Not in your area, but I'd guess a value of between $400 to $800 depending on what you find. But I'm not jonesing for a nailhead so I may be low.
     
  4. 41rodderz
    Joined: Sep 27, 2010
    Posts: 4,719

    41rodderz
    Member
    from Oregon

    From your point of view, you have to look at it as rebuilder for the engine(s)/trans. Hopefully he understands that as he is prohibiting you from a closer inspection. So he either knows something or not, but you are the one footing the bill not him .
     
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  5. 41rodderz
    Joined: Sep 27, 2010
    Posts: 4,719

    41rodderz
    Member
    from Oregon

    I have a nice Offy 3x2 intake for the 401/425 if you are interested down the road.
     
  6. Black Panther
    Joined: Jan 6, 2010
    Posts: 1,574

    Black Panther
    Member
    from SoCal

    I'd be careful with a 425...it can probably only go .030 over before having to be sonic tested to see if it can go further. GM basically took a 401 and bored it an 1/8" or .125 to come up with a 425. If that 425 is already. 030 over...it might need sleeving or similar expensive work to rebuild it. If you don't have a bore camera...they're cheap at Harbor Freight...like $75 and it can save your hide..
     
  7. Basement Sweeper
    Joined: Jan 24, 2020
    Posts: 81

    Basement Sweeper
    Member
    from Colorado

    Thanks for the input and caution on a 425 vs. a 401. I'm thinking $400-$500 for the engine and $300 for the transmission would be reasonable.
     
    Last edited: Jun 18, 2020
  8. Basement Sweeper
    Joined: Jan 24, 2020
    Posts: 81

    Basement Sweeper
    Member
    from Colorado

    And the answer to my question is $800 - $1,000 in the Denver Metro area. Today, I picked up a standard-bore complete 425 and matching ST400 switch-pitch transmission w/converter pulled from a 1966 Riviera for $800. The car was purchased new, driven by the original owner until the 1980s, and then parked next to her house where it sat until this year. Her relative is resurrecting the car and putting in a big block, so my T roadster gets the engine. I was able to pull the heads and pan, and everything looks rebuildable at this point in the tear-down. I might be able to get away with .020" overbore, so says my bore mic, so we'll see what my machinist says when we get to that point in the build. I've also located and looked at two other setups: a 1964 Wildcat with a 401/ST400 non switch-pitch combo and a 1965 Riviera with a 401/ST400 switch-pitch combo. The owner wants $1,000 each for the engine/transmission pairs.

    I must say, having wanted a nailhead since I was about five years old flipping through my father's old car magazines, it's pretty rewarding to go out into the garage and see one on the stand.
     
    clunker, rod1, j-jock and 5 others like this.
  9. 41rodderz
    Joined: Sep 27, 2010
    Posts: 4,719

    41rodderz
    Member
    from Oregon

    Good for you . Neat when a dream becomes reality.:cool:
     
  10. 51box
    Joined: Aug 31, 2005
    Posts: 885

    51box
    Member
    from MA

    They are very expensive to rebuild so my suggestion is to only pay core price for something you plan to tear apart. Once you’re in there, the list gets long.
     
  11. Basement Sweeper
    Joined: Jan 24, 2020
    Posts: 81

    Basement Sweeper
    Member
    from Colorado

    Core price seems to be about $500 for a complete engine and $300 for a complete ST400 switch-pitch transmission. At least in my region, the supply of 364/401/425 nailheads is very scarce, so core prices are higher. 65-66 ST400 switch-pitch cores are even scarcer. In the HAMB classifieds, people are asking between $500 - $800 for core nailheads engines alone all over the country. Ebay is more after shipping.

    You got me curious. What are your comparison engines for expense? Taking SBCs off the table since they are unfair outliers, I beg to differ on a 401/425 nailhead being "very" expensive to rebuild stock or mildly hopped up compared to most other "unique" engines (Ford flathead V8s, Caddies, Olds, early Hemis, Chevy 348/409--heck, even a 351 Windsor). People likely won't be able to buy a rebuildable, virgin, complete core for one of the above engines for less than $500. Most of these engines have little or no aftermarket head choices, so machine work is more extensive since the factory heads will need rebuilding.

    Parts: When debating what engine to run in the T Roadster earlier this year, I built a spreadsheet for all the parts and services I would most likely need. The parts for completely rebuilding the engine from intake manifold to oil pan, water pump to flexplate come in at around $2,200 (includes valves, guides, seats), and I used higher prices when given a range. Add $330 if it needs rocker arms and shafts. The only original parts I would keep would be the crank, rods, flexplate, and balancer. I haven't done too much scrounging for best prices and used only three different websites for pricing, so I can likely decrease this amount a little. Of course, this estimate will increase if the crank/rods/balancer are junk, but I don't see any evidence they won't be usable.

    Machine Work (actual prices from my machinist):
    Block: magnaflux, bore, hone (no torque plate), grind/polish crank, press new pistons, balance rotating assembly, install cam bearings, I'll install freeze plugs: $1,130. This price will go up if the large rod ends need resizing.

    Heads, assuming the worst: magnaflux, 16 new guides, valve job (try and keep the soft seats), surface to match cc's: $680. I might be able to save here if only the exhaust seats need replacing and there is little wear on the intakes to get even valve height within tolerance and if not all guides need replacing. Factor in the stainless valves, mild springs, and keepers already included in the parts tally above, there's about $1,000 in the heads alone.

    Breakdown:
    Parts for a long block: approx. $2,200
    Machine Work: $1,800
    Grand total: $4,000

    That's not really "expensive" let alone "very expensive" for a well-built engine of this vintage. I'm sure people who live in states with lower wages and cost of living can have the machine work done for less, but not much less at a quality machine shop that knows its way around vintage engines. Besides, I don't live in a region with cheap labor and cost of living, and I'm darn happy about that--I have world-class concert halls, museums, theaters, restaurants, and drag strip all within 40 miles.:D As for a Ford flathead V8, Caddy, Olds, early Hemi, or 409, I'm not going to take the time to price parts, but I'd wager parts will cost more than a 425. Machining labor will be the same (likely more for a flathead and Hemi).

    In the end, the pricing looks about just as expensive as most other engines. I'm all ears for debating since I have no issue saving money where I can and admit I'm a novice when it comes to 425 nailheads. The more info people can post on where to find parts, the better.
     
    Last edited: Jun 19, 2020
  12. khead47
    Joined: Mar 29, 2010
    Posts: 1,666

    khead47
    ALLIANCE MEMBER

    You do not sound like a novice ! You have done some homework !
     
    Basement Sweeper likes this.
  13. Basement Sweeper
    Joined: Jan 24, 2020
    Posts: 81

    Basement Sweeper
    Member
    from Colorado

    Thanks, I've read the entire site researching nailheads before looking for one. Most of my parts from the above $2,200 tally come from him.
     
    Last edited: Jun 18, 2020
    hidez57 likes this.
  14. NICK Cee
    Joined: Nov 27, 2009
    Posts: 82

    NICK Cee
    Member
    from Tucson, AZ

    I just picked a '65 425 and tranny combo up from California..$1300 for all with pulleys, brackets, manifolds..ect. Looks like it might need a sleeve but all std. On a month waiting list for the machine shop...
     
  15. Harold Cox
    Joined: Jul 9, 2020
    Posts: 5

    Harold Cox
    Member

    Thanks for the brake down on build cost. I recently purchased a 66 225 with a 401/400 running and driving for the drive train. Pretty dang nice car with 80k miles other than the interior being trashed by the sun and rats. I always wanted one and figured I would go through it some day. Might even drop it in the 53 and do away with the tube some day.

     

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