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Technical Sonic Testing - Three Flathead Blocks - All bored 3 3/8!

Discussion in 'Traditional Hot Rods' started by Bored&Stroked, Jan 15, 2015.

  1. Hey Gang:

    Just got back from looking at some flathead blocks today - was going to buy three of them, yet some bastard got there before me and reserved TWO of them. Missed those two by ONE damn day! Crap.

    Anyway, all three blocks were already bored and raced at 3 3/8" - what many consider to be the max bore for these engines (just common folk lore). So, I brought my trusty sonic tester with me as I wanted to know how much bore thickness was actually left - thought it was a good opportunity:

    1) Block #1: 59 -- The minimum wall thickness was about .120 or so (thrust side), the opposite side was closer to .175 or so. This block had some really nice port/relief work and 1.750 intakes. I went ahead and bought it . . . seems to be worth the gamble.

    2) Block #2: 59L -- It was almost exactly the same as the 59 - was not any thicker as some seem to claim.

    3) Block #3: 1941-42 Merc Keystone: It was about .090 at the thinnest spot and about .120 in most places. Overall, I think it would be about .020 to .030 thinner than the two 59X blocks.

    So - with these readings, I think all three blocks can easily go to 3 3/8 + .030 . . . probably 3 7/16 if need be (accept for the Merc block). I really don't like to get much below .080 on cylinder wall thickness for a naturally aspirated motor - and .100 to .120 on a blown motor.

    Good news in that these blocks had more meat in them than I would have suspected. I'll post pictures once the block is cleaned up, magged, etc.. (will be a few weeks at the very least - have a lot of other flathead fish to fry!).

  2. banjorear
    Joined: Jul 30, 2004
    Posts: 4,405


    Please do. I would like to see those picts. for I also have a block that is at 3 3/8ths.
  3. 29AVEE8
    Joined: Jun 28, 2008
    Posts: 1,384


    Interesting. Kind of fly's in the face of what has been accepted info.
  4. gillman
    Joined: Apr 16, 2005
    Posts: 12

    from n.j.

    I'm that bastard! LOL Got plans for both. Glad you sonic checked them,I feel better now,basically rolled the dice from what the owner told me.
    If you have any more info please pass it along.
    Kiwi 4d likes this.

  5. banjorear
    Joined: Jul 30, 2004
    Posts: 4,405


    Right. Weren't those Merc blocks supposed to be the cat's pajamas?
  6. gillman
    Joined: Apr 16, 2005
    Posts: 12

    from n.j.

    That's the conventional wisdom,might be thin because of water jacket erosion??
  7. Probably more like core shift in casting process.
  8. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,620

    Rusty O'Toole

    Old blocks before 1960, and possibly before 1955, are a bit of a crap shoot. The casting technology was not perfect and there was more core shift than on newer systems. To reduce scrappage they just made the castings thicker. So, if you get a good one, there is plenty of metal all around the cylinder. If it is a bit off, you still have plenty to hold it together and even rebore and rebuild 2 or 3 times.

    Before sonic testing there was no way to tell if you had a good one or bad one short of cutting the casting in half. You had to go easy or risk ruining your motor, and it was possible to have a thin cylinder and not find out about it until it was done and on the road.

    The first motor to take full advantage of the new thin wall casting techniques was the Ford 221- 260 - 289- 302 series that debuted in 1961 or 62. It was 200 pounds lighter than the engine it replaced.
  9. Now that is funny! I didn't mean to offend the unknown you! :)

    I think you'll be okay on the deal - I inspected both your blocks and it looks like both will be good. The Merc is a bit thinner, but can probably go another .030 unless some of the bores are really pitted.

    Good news is that I checked out two more blocks they had and let them know that both had some really poor prior machine work on them - would be a real problem if somebody purchased them. The vendor was going to take them off the auction site - stand up guys, going to do the right thing.

    Good luck on the deal.
  10. Yeah, and what I hate is that in many cases they can stand a single overbore, then they're done!
  11. banjorear
    Joined: Jul 30, 2004
    Posts: 4,405


    Where is this mystical honey hole of flathead blocks? Seems like it is somewhere between NJ and OH.
  12. interesting , i had no idea how thick any cylinder wall was . my first gut reaction was .090 to .120 seams awful thin. does anyone know how that compares to a typical thin wall SBC of SBF?
  13. I should clarify that I'd prefer to NOT go under .120 . . . probably .120-150 on a new build -- and really I never bore past 3 5/16 on a new engine (so I have a lot of cylinder wall left - usually .150+). But, if you have an old block that has had a lot of work done to it (like these three blocks), then it is worth considering trying to save the block and building an engine. Somebody else had invested all the time in the porting/relief work on these three engines . . . would be cool to run them again if at all possible.

    Are they still a bit of a gamble? Yes - in that there can be a rust pocket, casting imperfection or other issue that may cause a cylinder to be bad . . . and, one might even develop a crack, split a cylinder wall, potentially have a bit more heat issues, have ring seating problems and it may not work out. But hey - sometimes you gotta roll those dice.

    I would not build one for the purpose of a lot of future miles - probably something fun, big cubes and some screwing around. With that said, you'll still invest quite a bit in one of these engines - so they're not for the guy looking to have a nice cruiser that is mild mannered and runs for 30,000 miles. But if you have some parts to play with . . . and your curious as to "Hmmm, I wonder what a big-ass stroker motor might run like????", then why not.

    What I'll do is have the block hot tanked, magged and rough bored - then I'll pressure test . . . before doing anything else. This engine will be a 'screw around' type of deal . . . big, snotty and nasty . . . hopefully! :)
    Last edited: Jan 16, 2015
  14. Nice score Dale. What I worry about more on these old blocks isn't the actual thickness it's the ones that have been left for years with water standing in the jackets rotting them from the outside in. Too many times I've bored one to find swiss cheese in the bottom of a cylinder or two. o_O
  15. banjorear
    Joined: Jul 30, 2004
    Posts: 4,405


    I was thinking the same with mine. I have all the "goodies" to put into one. I was thinking of using some outrageous cam and trying out some of the tricks that I've read/learned/seen along the way. If it doesn't work out, put back in your "milder" engine.
  16. Exactly! No high hopes . . . just something to experiment with and MAYBE have some fun for awhile. What I really need to go with this 'treasure' is a big billet stroker crankshaft - lightweight, strong and about 4.375+!
  17. gillman
    Joined: Apr 16, 2005
    Posts: 12

    from n.j.

    No offense taken! I got a good chuckle,been called a lot worse!
    Anyway we are on the same page as to what is the potential pitfalls of resurrecting old speed parts. I'm going to do the same as you,hot tank and magnaflux,then go from there.
    Custom pistons don't scare me as long as rings are available,plus I have a couple of good 4.0 and 4.125 cranks.
    I'll post my findings after the hot tank and clean up. Should be interesting!
  18. banjorear
    Joined: Jul 30, 2004
    Posts: 4,405


    I've got fingers crossed that I can re-use the 3 3/8th's jugs that came with the motor. They are old cast 3 ringers, but we'll see how the bores check out.
  19. Nice to see a few of us flathead nuts just building something for the hell of it and having some fun! Heck, with the other box of parts that I acquired while I was there, I'll be okay on this deal no matter what happens.

    Build em' boys! . . . Build em' big, nasty and barking like a dog crapping razor blades! :eek:
    draider likes this.
  20. Bader2
    Joined: May 19, 2014
    Posts: 1,143


    Just outa curiosity what's a bored block go for where you are?
  21. louisb
    Joined: Oct 13, 2008
    Posts: 1,126


    I have been keeping an eye out for good blocks in my area, North FL, and I see them going for $300-$400. Questionable ones for about half.

  22. If a block has been taken apart, hot tanked and magged, I'd say it is worth $400 - $500 . . . just what my gut feel is. It is hard to find one sonic tested, so that is why I bought my own tester (and for porting as well). Is even a better deal if they've been pressure tested - which I do on my own blocks.

    Truth be told, if you can find a good one for $500 - it is a bargain (as compared to finding core engines, spending hours to take them apart, hauling them to a shop and paying $100 - $200 just to find they're junk).
  23. banjorear
    Joined: Jul 30, 2004
    Posts: 4,405


    If it helps, two years ago I sold a bare '53 block that was standard bore, magg'd, and clean for $600. It was not pressure tested. Only reason I sold it was I was moving and needed to cut back on weight. Otherwise, I would have never let it go.
  24. awelker
    Joined: Jan 7, 2008
    Posts: 65


    Glad to hear those blocks found a good home. I studied them on the auction site and just were a little to far to drive for possible junk.

    Dale - interesting on the wall thicknesses. Good info.

  25. As I'm building one for my 32 and have seen a few and talked to some guys I consider real experts . . . I don't believe they have any advantage at all. Actually, I've heard from some guys who did a LOT of this, that they were more prone to cracking in the relief area than later 59x blocks. When I get mine back from the machine shop, will sonic test it and see if it compares to the one I just tested -- who knows, maybe they're actually 'thinner' than the 59X series (would not surprise me one bit.)
  26. PackardV8
    Joined: Jun 7, 2007
    Posts: 1,077


    X2 on finding bad news in old blocks.

    (quote)Nice score Dale. What I worry about more on these old blocks isn't the actual thickness it's the ones that have been left for years with water standing in the jackets rotting them from the outside in. Too many times I've bored one to find swiss cheese in the bottom of a cylinder or two.(/quote)

    Building a Packard V8 for a guy wanted to keep the numbers-matching deal on a high-dollar resto. I told him the block was the gnastiest water jackets I'd ever seen. Packards have .300" thick walls, but when we bored this one .030", as soon as it sat overnight, rust spots started appearing inside #8. We bored it for a sleeve and big holes began opening up.

    Whatever crappage someone had put in the radiator had filled most of the cooling system solid and then eaten through 1/4" of arn.

    Bad thing is, solid rust can fork your sonic test.

    jack vines
  27. ronnieroadster
    Joined: Sep 9, 2004
    Posts: 1,033


    Dale your testing makes me feel much better about the 59A I have that's 3-7/16 bore. The block is assembled with a Merc crank its to have only been run for a very short period I suspect head gasket issues saved this motor from being worn out when it was first built. Maybe its time to freshen her up.
  28. Hey Ron, why not give her a try and see how it works out? If the bores are like these, then you probably have about .090 thickness . . . which is thin, but will probably still work.
  29. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,910

    dirty old man
    Member Emeritus

    Sometime back in the late 50s, not sure any closer than that, my dirt track racing buddy, his brother and I were rolling North from Macon, GA on US 41 after a race at the old half mile Central City Park track in Macon. I was the "gopher"', still in my teens.
    As we passed thru the little town of Bolingbroke, about 10-15 miles North of Macon, we spotted a shop with a lot of old Fords parked around the lot in various stages of disrepair, and stopped to look around. We always did this when the opportunity arose, and you never knew what you'd find.
    The owner was there and a real old timer, friendly as Hell. My buddy did the talking and soon the old man was showing us his "treasures", including a block he said was a copy of a Ford flathead that came out of a Japanese tank. Where he got it I'll never know, but I remember it every time I pass by on I75, which passes by just to the East of the old hwy 41 thru town.
    That block, looking thru the coolant holes in the deck, appeared to have cylinder walls almost 3/8" thick.! He wouldn't even talk about selling it.
  30. Bert Kollar
    Joined: Jan 10, 2007
    Posts: 1,220

    Bert Kollar

    What type or brand sonic tester do you use. I have two hemi blocks I have to check before I create another boat anchor. I have scrapped two blocks after machining and am running out of money. Is there an inexpensive tester I can buy and check them myself or should I have a shop check them.

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