Rebuilt 425 now junk?

Discussion in ''Da Nailhead' started by 56buickboy, Aug 5, 2007.

  1. Schurkey

    Schurkey Silver Level contributor

    Absolutely true.

    Ideally, you'd hone the cylinders (with a torque plate) after installing the sleeve. But then, ideally, this would have been caught--and sleeved or otherwise repaired--long ago. You're probably going to end up with some extra piston-to-wall clearance, but that doesn't mean the party has to end. Your machinist will have to measure--and be careful.

    Why? IF (big IF) you have seven good cylinders, there's no reason to carve 'em out and shove in sleeves. Sleeve the one bad hole. The question here is whether or not the other seven are good.

    Even if you sleeve all eight, you could still have the machinist bore 'em to fit the pistons.

    That assumes the machinist assembled the engine. If someone else did the assembly, they may have caused the gouge--and the machinist may do fine work.
  2. 56buickboy

    56buickboy Well-Known Member

    Thanks Tom, Ive got them soaking in CRC but after 2 days it is still just sitting on top of the pistons.
    I've never heard of Muriatic acid but will see if I can get some and give it a try.
    Its hard to estimate how deep the rust damage is in the cylinders but I'm guessing that even starting with a "standard" bore I will be lucky to get away with a .030' oversize.

    Schurkey - I am on to block #2. The first block with the gouge in the bore is just sitting in the shed in case one day it may be useful. The gouge appears to be a casting flaw due to thin cylinder walls as opposed to an assembly issue. Thanks for the comments.
  3. 56buickboy

    56buickboy Well-Known Member

    Hi guys

    Just an update on the 425 blocks and some more questions.

    I took Toms advice and tried acid to remove the frozen pistons. After 2 days the acid had hardly touched them. Those cast pistons didn't give up easily.
    The acid softened the crown and I was able to use a big punch to knock the crown off from underneath, before chiselling the skirt to break the wall tension and then hammer them out.

    Unfortunately the second block is also badly corroded in some cylinders so will have to be sleeved, but at least I will end up with a good solid block.

    Doc......... When you sleeved your block did it end up with a wet or dry sleeve? Can you remember how much material was removed before inserting the liner? and did you use off the shelf pistons?

    If you leave a step at the bottom of the bore for the liner to sit on / into, how does that affect the piston skirt as it comes out the bottom of the cylinder? or is the sleeve stepped as well.

    I found a site:

    they can make just about any type of sleeve, wet / dry, cast iron / steel
    to any dimension. They also make one with a flanged top, or 2 and 3 flange.

    It looks like the minimum wall thickness needs to be .093" if the original cylinder wall is only about .090" (in places), (now down to .030 with a .060 oversize) I will probably end up into the water gallery and have to use a wet liner?

    Is there enough material around the top of the cylinder for it to be machined to accept a flanged insert?

    Any advice, experience, or recommendations on what I should use would be gratefully received.

    Thanks, Ross
  4. doc

    doc Well-Known Member

    Ross, the best advice about the sleeve question will come from your machinist....But on my engine we used a dry sleeve, interference fit, with a ledge at the bottom of the cyl wall to make a ''blind'' sleeve installation.... then the steel sleeve was packed in dry ice and the block warmed.... then the sleeve crammed in and when it got near the bottom , driven on in with a sledge[12lb] and a oak block......then the top was cut off flush with the deck... trust me it aint going any where... and will last forever.....
  5. 56buickboy

    56buickboy Well-Known Member

    Thanks Doc
    I will find a good machinist and take it from there.

  6. bills2x4cat

    bills2x4cat Well-Known Member

    If you are not suppose to belive what anyone tells you does that mean that hes not suppose to belive what you tell him Tom? Or are you the exception to the rule?
  7. 64LeSabre455

    64LeSabre455 Well-Known Member

    I am interested in what the outcome was? Were you able to fix up that 425?
    Please let us know!!
  8. 56buickboy

    56buickboy Well-Known Member

    Hi guys, sorry at this point I am unable to give an update, both blocks are still sitting tucked up in the shed due to other committments (wifes VW rebuild, amongst other things) but I will give a progress report and hopefully photos when I make progress.

  9. Fragzem

    Fragzem Well-Known Member

    out of curiosity sake, what does it take to turn a 401 into a 425?
  10. doc

    doc Well-Known Member

    Basicly , a 425 block,,,,,because when you bore a 401 enough to take 425 pistons, the cyl walls are left so thin that the engine will run hot at the drop of a, add 35 to 40 years of internal rust to that and it gets even worse....
    You can do it by boring and then sleeving all 8 cyls, but that would be so expensive that it would be prohibitive....some one who owns or works at a machine shop could do this but to pay full price , aint gonna fly....
    Cheaper to find a 425 block.....:Brow: :Brow:
  11. Fragzem

    Fragzem Well-Known Member

    that sounds about right, doc. Thanks!!

  12. 56buickboy

    56buickboy Well-Known Member

    I just had both my 66 MW (425) Blocks sonic tested. The first had been bored .060 which revealed a casting flaw, and the second was a standard bore with bad rusting after being frozen and left outside.

    If the first block had been sonic checked PRIOR to being "rebuilt" it may have been salvageable by offset boring apparently. Six of the cylinders now have wall thicknesses under .100 with some as low as .062

    The second STD block (rusted) ranges from .095 - .337 but the engine machinist isn't happy to sleeve either block due to the thin walls.

    So I am keen to find another 425 block (with your help) and possibly have it sonic checked prior to shipping to NZ. I have seen a few advertised in various states of repair, but some people will not freight which is understandable, and depending on where in the country are expensive to get to CA for shipping.

    As always advice and suggestions appreciated. I would love to get a decent block to continue with the project.

  13. SpecialWagon65

    SpecialWagon65 Ted Nagel

    I have A KW engine sitting = Let me get it back from its storage area and check it out.
    I think I can start it up and post a video...
    it was a running engine just had low oil pressure.
    I was in NZ 2/08 what a beautiful place!
  14. John Codman

    John Codman Platinum Level Contributor

    As a matter of practicality, I would not go more then .030 on a 425 block without a sleeve. I would still save both of the blocks that you have. With the application of significant $$, both can probably be saved. My opinion is that a machine shop that would bore a 425 .060" is not familiar with Nailheads. Either you need a different shop, or the one that you have needs some edjamication.
  15. nailheadnut

    nailheadnut Riviera addict

    Interesting read, thanks. As I read it a couple of thoughts came to mind; Tom partially addressed this. Everyone I know who has bored a 425 block 0.060" over has had overheating problems. If it's possible to sleeve every cylinder back to the original bore and use OE diameter pistons, you would probably have a cooler running engine.

    Thought #2 . You're talking about going back to the original 322. What transmission, rear end, etc are you using to put this 425 into your body. The 425 doesn't bolt up to the tranmission you've got, the bellhousings are different diameters. The cranks for the dynaflows have different hubs on the back than the cranks for the ST400's. The older bodied cars use a torque tube where the later cars use an open drive shaft. I'm just curious about how you're adapting a 401/425 to what ever transmission and chassis you have.

  16. 56buickboy

    56buickboy Well-Known Member

    Thanks Ted, that sounds positive and much appreciated.

    John, I purchased the engine as a rebuilt motor and as stated previously decided to have a look inside (fussy mechanic coming out). The shop that did the work before I bought it obviously had no Nailhead knowledge. Apart from over boring and advising the previous owner it would not be a problem, the crank had new bearings installed but was never machined or polished and looked to have scuff marks from the rod bolts when the pistons were reinstalled. The engine was dirty throughout and oil gallery plugs had not been removed, the list goes on.

    The machinist that did the sonic testing is very experiened with V8 race engines and has a good reputation but from what I understand has limited Nailhead knowledge as well. He has sleeved many engines but believed the cylinder walls were to thin to sleeve without causing further problems.
    The Nailhead engine down here is rare so finding anyone with sound knowledge or experience is tough. Hopefully my time spent here learning and advice from the real experts who have done numerous Nailhead builds will be enough to get the job done right.

    Tom has mentioned hard blocking to support the cylinders and then installing sleeves, so It may still be an option, but Doug (KDML) had a cylinder broken with sleeve install and minimum thickness was .100.

    Just really posting the information for the benefit of others thinking about rebuilding, SONIC test first!! it has been said many times.

    Anyone looking for a nice coffee table using a 425 as a base? I have 2 options with your choice of Buick red or green :laugh:


    ---------- Post added at 11:36 AM ---------- Previous post was at 11:18 AM ----------


    I am rebuilding the car and still have the 322 but have donated the dynaflow to another guy down here that needed parts. I am converting to an open driveline no matter what engine I use. I plan on using a Ford 9inch rear end on Chev truck trailing arms. I have 2x SP400 transmissions but if I end up having to use the 322 will use a trans adapter and possibly an overdrive trans.

    Im not sure if the SP400 can be used on the Transmissionadapters kit, I think the kit is designed for Chev transmissions and as you mentioned the earlier engine has a different size bellhousing.

    Sleeving back to Standard bore would be the ideal plan but the risk is damaging the block (with extremely thin walls) in the process. I suppose there is nothing to lose trying, although it just may be more economical to purchase another engine.

  17. bhambulldog

    bhambulldog 1955 76-RoadmasterRiviera

    Here's my experience with sleeving;
    In 1975 our 322 dropped one valve each on two cylinders. Both pistons went to pieces. One of the cylinders was not badly damaged. Honing fixed it up.
    The other cylinder was badly gouged. A sleeve was placed in that cylinder.
    All the bores are at the original diameter. Original type pistons were installed.

    37 years later, the 322 is still running strong.

    I would'nt say your 425 is now junk.
  18. 56buickboy

    56buickboy Well-Known Member

    Hi all, Happy New Year

    The hunt for a nice 425 block continues.

    I have found this STD bore MW 425 block for sale in Ohio and the owner sent it to the machine shop for sonic checking on my behalf.

    What do you all think? Looks like .010" will clean it up. I have seen threads that mention .150" minimum wall thickness. If I hard block this will any of these cylinders need sleeving? It will be a street engine only with 1/4 mile fun maybe once a year. Opinions appreciated. (I hope it is readable, click it a couple of times and it should get bigger,- worked for me)

    Thanks, Ross

    Front of block is top of page

    Attached Files:

  19. telriv

    telriv Well-Known Member

    As you can see Ross from the results that some of the cylinders are thin to start out with. Numbers 1/3/7 are the worst. It is true, as far as my beliefs, that because of the weight of the stock reciprocating assembly of a NailHead that the cylinder wall thickness should be NO LESS than .150". As you can see they aren't that thick when new. With that said what I would do & recommend, even on stock rebuilds, is to use epoxy in the bottom of the block to the bottom of the big freeze plugs. This will help to stabilize the bottom of the block. Of course the insides need to be cleaned &, again, I use muriatic acid to accomplish this. At the top of the block the deck is MUCH thicker because it needs to hold the torquing of the head bolts. Just don't remove TOO much from the top of the deck to make it square. Buick's machining work was pretty good from the factory, usually within .001"-.002" on each side. The average deck height for a 401/425 is usually between 10.014"-10.020" with usually no more than .001"-.002" side to side. The measurement for the main saddles is 2.687". If the engine was bored .030" that would mean that you are only removing .015" from the cylinder wall. Also as you can see core shift was a major problem in the later years because they knew that the days of the "Nail" were coming to a close. I've been told by a good source that any blocks that came out of the casting plant with centered bores were removed from the line & sent to the racers. If you can & if the machinist will do it, have the main bores measured. Don't just assume that it will need align honing or boring. Again, good machining processes from the factory. By doing the align process you will end up with a forever loose timing chain. IF it has to be done then have it align bored only not honed. With align boring you can set it up to remove more from the main caps than the block. Were normally only talking a few thousandths here.
    More to come as needed.

    Tom T.
  20. 56buickboy

    56buickboy Well-Known Member

    Thank you Tom for your advice, it is always appreciated. Can you explain a bit further your comment regarding # 1/3/7 being the worst. I see other cylinders with lower numbers. Where are you looking for areas of concern? Are you looking for variation within a cylinder, or low numbers on the thrust side, thin walls lower in the cylinder? I need more clarification please. I numbered the picture to reduce any confusion.

    Attached Files:

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