Register now to get rid of these ads!

Technical Calling all Flathead V8 Crack Experts!

Discussion in 'Traditional Hot Rods' started by NbdyHome2, Dec 5, 2020.


Run it? Trash it?

Poll closed Dec 12, 2020.
  1. Run it.

  2. Trash it.

  1. NbdyHome2
    Joined: Feb 26, 2019
    Posts: 99



    I recently brought a '46 Flathead V8 to a machine shop that was recommended to me after calling around for days to see if anybody would take the boat anchor that's been scamming out of rent in my garage. The shop is 2 hours away unfortunately. The engine has been there (only to be cleaned, magnafluxed, decked, align honed, and bored .060 over) since before Halloween. I don't remember when I brought it exactly, just that it's been a LONG time.

    I got a call from them finally yesterday and they notified me that there were cracks, one of which might be a career ender. But they also said that EVERYTHING else looks GREAT! Trying to figure out how to attach photos now....

    97058.jpeg This image of the lifter valley is better looked at with your head tilted to the left. This is the major one in question that they say might be the block killer. Anybody agree or disagree? What would happen if I built it anyway? Are we in danger of blowing up? Catching on fire?
    97060.jpeg This is a 'gouge' in a lifter bore according to the shop.
    97056.jpeg Crack along the oil pan sealing surface.
    97057.jpeg Dent in the deck. 97059.jpeg And finally another oil pan area crack.

    My question to you all is this: Would you run it? Or is it not worth it?

    The shop will find out on Monday if they can repair the lifter valley crack....they didn't seem to think the others were worth worrying about.

    This isn't going to be a high performance machine by any means. I'm talking daily driver here, but definitely daily. I don't want it to sit. But then again, I also don't want to pay a lot of money to fix a cracked block that will disintegrate either.

    Any and all opinions are greatly appreciated and respected as you all know way more than I do. Thanks in advance.
  2. alchemy
    Joined: Sep 27, 2002
    Posts: 17,092


    Any of those cracks that lead to water will need repair at the very least. But, with so many cracks I'd say that you would be wiser to find another block. There's no way you could "run that as is". It would squirt out every side of the engine.

    But, the little gouge in the lifter bore wouldn't scare me, so you are safe there.
    Automotive Stud and 1927graham like this.
  3. 21studder
    Joined: Nov 23, 2019
    Posts: 11

    from Finland

    Too many cracks, I would find another block.
  4. Fortunateson
    Joined: Apr 30, 2012
    Posts: 4,180


    The first pan rail pic crack has two possible solutions... drill the ends of the crack and then "v" the crack a bit and fill with JB Weld. This is supposed to work as the crack is only on the gasket area of the rail. Another tip I heard from Auliz in Sweden is that you can add some cement down there to close it up. He says that it is so low on th eg lock that it would not affect the cooling system. I've never tried either way but I'm intrigued.
    Automotive Stud and VANDENPLAS like this.

  5. trevorsworth
    Joined: Aug 3, 2020
    Posts: 812


    I think with flatheads the general consensus here is to run it if it runs, so if people are already saying no out of the gate it’s probably a sign.

    As for me, not an expert, but with that many visible cracks, I would be concerned about there being more that I can’t see, and something might be goofed up with this block’s metallurgy for it to be so brittle. Bare blocks for these things aren’t so hard to come by that it makes much sense to get mired in repairs on this one. You already have it stripped, so find another block to put the guts in and save yourself time, money and headache later.
    VANDENPLAS likes this.
  6. WB69
    Joined: Dec 7, 2008
    Posts: 1,673


    That's a lot of cracks. Just saying. I sure someone out there could have a fix and run it.
  7. I have a complete 59A motor of unknown condition. PM me if interested.
  8. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,003

    from Zoar, Ohio

    A crack along the pan rail probably indicates the block was lying around outside full of water and froze.
    Cut you losses.
    Last edited: Dec 5, 2020
  9. GordonC
    Joined: Mar 6, 2006
    Posts: 2,442


    Mine had a few of the typical steam hole water cracks which I had repaired. Not as many cracks as that has though. Why spend good money after bad. You could get good parts, get it all assembled, start running it and then ruin those good parts. Trying to figure out where the problems might be coming from after it's built will be a major pain in the ass. If it were me I would pass on that motor. Do it once and do it right.
    Spoggie and 5window like this.
  10. Aaron D.
    Joined: Oct 27, 2015
    Posts: 998

    Aaron D.

    I agree with Petejoe. To me, those cracks indicate the block froze, expanded, and cracked. The lifter valley crack and the pan rail cracks all go to the water jacket. Pressure checking the block would tell you if those cracks go all the way into the water jacket (which I bet they do). Personally, I wouldn't waste the money trying to fix that block if I could find another one.
  11. Yep, Aaron D. beat me to it but if it were mine I would definitely pressure check it before I went any further. That should tell the tale.
    Speed Gems likes this.
  12. quickchangeV8
    Joined: Dec 7, 2010
    Posts: 416


    Those pan rail cracks are the death knell of this block. I wouldn't put any more money towards this flathead block as there are just too many cracks to deal with and it will always be leaking coolant. Load it up on your truck and head down to the marina. Maybe someone down there could use a good boat anchor.
  13. dan c
    Joined: Jan 30, 2012
    Posts: 2,222

    dan c

    years ago, i threw one away with a cracked pan rail, but many today would repair it. i agree that your block will cost $$$ to repair and that you should look for another one!
  14. NbdyHome2
    Joined: Feb 26, 2019
    Posts: 99


    Thank you all for the input so far. I value all of your opinions. So far it's looking like that trip to the marina is the most viable option.
  15. 6sally6
    Joined: Feb 16, 2014
    Posts: 1,612


    Hey....put it on Craig's List!!! Just ask $200.00 bucks though. Too cheap and nobody will buy it!

    I would beat it up real good so 10 years from now somebody will find it in a dump and be on here asking the same questions......."Can this be fixed"????:rolleyes:
  16. Flathead Dave
    Joined: Mar 21, 2014
    Posts: 3,423

    Flathead Dave
    from So. Cal.

    Find another block. Cut your loses.
    Cost too much to repair.

    Sent from my SM-G973U using The H.A.M.B. mobile app
  17. RidgeRunner
    Joined: Feb 9, 2007
    Posts: 906

    from Western MA

    Probably better to put any money into building on a better foundation for a road driver to keep your mind at ease if nothing else.

    I don't think it's ready for the Marina quite yet though. I'd wager that after a block filling to run it dry it might make a few good 1/8th and 1/4 passes in someone's race rig.

    belair likes this.
  18. Automotive Stud
    Joined: Sep 26, 2004
    Posts: 4,173

    Automotive Stud

    I have a flathead I got in trade that had all the machine work done and a new bottom end in it, but it had pan rail cracks slightly bigger than yours pictured. I had nothing to lose, so I did what fortunateson said, veed them out with a dremel and packed them with epoxy. I put a few thousand miles on the motor over the last few years with no issues. I run a 4 pound radiator cap.

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.