I have a MW code 425 that was "rebuilt" when I purchased it. It has new .060 pistons (why I ask), rings and bearings, and has had a valve grind, but has been sitting for over 2 years. For the cost of a gasket set I decided to pull it apart after reading some of the posts and warnings from all you more experienced nailhead experts. Fortunately I did. Unfortunately the # 1 cylinder has a casting flaw half way down the bore that looks to be at least 040 deep and it backs onto the water gallery. I cant believe this wasn't seen during / after the rebore.:shock: I have read some brief posts on sleeving the block and was wondering is this a successful solution, and if so I have the following questions. 1. Do all 8 cylinders need to be sleeved to keep cylinder sizes even. 2. Does this take the bore back to standard or undersize 3. What piston options are available once sleeved ( 364 / 401 ) or custom 4 Are my new cast 060 pistons any good to anybody or shall I give them to the kids to play with. 5 Does anyone have a standard bore 425 block for sale? that will bolt up to a SP400 and could be shipped to New Zealand. Any help/advice appreciated. Thanks Ross
SLeeving is a good way to 'save' a block. Many of the little import cars such as the Hondas use sleeves in all cylinders to allow for a larger bore than the factory block allows. If the other cylinders are infact good and have enough material, you should only need to sleeve the one bad cylinder. You should be able to have the sleeve machined to accept the pistons you have now-.060". You might want to have the block sonic tested to see if any other issues are present in other cylinders, if they check out ok-have the bad cylinder sleeved by a competent machine shop and you should be ok. You COULD have all 8 cyls sleeved to accept the .060" pistions and have a very strong set up. You should look in to the costs first and make sure a reputable shop does this work for you.
Thanks Joe for the response, but I am still a bit confused. Surely if the original cylinder walls are thin then machining the bore larger to accept sleeves (that will accept my 060" pistons) will only make the problem worse, or is the critical factor the top and base of the bore where the casting is thicker. Am I missing something obvious?
Don't believe what anyone tells you. If in fact you do have the cylinder sleeved make absolutely sure they PIN the sleeve top & bottom or else it WILL move. With an .060" overbore the block should be sonic tested. I guarantee that there will be more the one cylinder with a thin bore. To get by that you could have the block filled with "Hard Bloc" about an inch or so to help stiffen & support the cylinders better. In actuality the engine will run cooler because there is more coolant flowing faster around the tops of the cylinders.
I gave up my old block for that reason.......I think .060" oversize is just asking for trouble. If that flaw is below the ring travel, maybe it would be possible to have it welded and carefully ground to the approximate surface of the cylinder wall? I don't see how that would matter as long as the rings were above the spot. :idea2: Maybe I'm way off base here, just an idea. ou: Otherwise it might be easier to just try to find a 401 block instead.
The new sleeve takes the place of the structural integrity of the cyl walls. In many applications, the walls are taken out completely and the sleeve replaces it. I am no engine machinist by any means, so I don't have all of the specifics. Tom is right, make sure the sleeve(s) are pinned to keep them from floating in the block. Hard bloc'ing it will also help keep the new sleeve as well as the other cyl walls from moving/flexing.
Thanks for the idea, but unfortunately the flaw is about 2 1/2 inches down the bore so still in the ring travel. As Tom mentioned above, the other cylinders are probably thin as well. I am currently considering all my options, another block - although freight to NZ wont be cheap, sleeving the 425 or rebuilding the original 322. I was so looking forward to having a big block in the 56 :grin:
I don't know where you people get your stuff machined, but a competent machinist dosen't need to pin a sleeve. There should be a ridge left on the bottom to keep it from moving down and the head keeps it from moving up. Sleeves are interferance fit, and are usually cooled while the block is heated then pressed in. I've seen many blocks that have had sleeves installed that you can not tell were sleeved. The only problem is that the adjacent cylinder's concentricity is affected a tad.
To do the job rite you need to sleeve all 8 holes and buy new pistons. Any one shoddy enough to build an engine with a goudge in the cyl wall like that is a hack. I wouldn't trust anything else they did including there valve job, crank grind, rod recon, etc
Tom I didn't know that. Goes to show you do learn something new everyday. Is the same true for a 455 block??
Thanks guys for the updates and information. I have spoken to 2 machine shops here and was told no one in NZ does sonic testing except maybe Air New Zealand. Without seeing the block the first guy said the flaw may never cause a problem and advised that sleeving would distort the neighbouring bore. The second shop said definately sleeve the cylinder, the first cylinder costing about $400 and any other cylinders cheaper after that because of the initial machine set up costs, once they found a sleeve big enough. For that price and peace of mind I am looking for another 401-425 block or engine and will start again, and use this one for parts. I was told the .060 cast pistons in the motor I have owe him $1200? I would hope for that price you could buy a nice set of forged ones? The guy I bought the engine off is now in California and doing his best to source another engine for me. He is in the freight industry and is going to take care of the shipping. The dream of a big block in the 56 lives again.
I have managed to find a standard bore MW 425 block, (siezed pistons) with crank and rods, cam etc, for $300, and free shipping to NZ. Once I have freed it up, is it likely I will be able to bore it .010" or will a rusted bore need .030" to clean it up properly, or is this an unknown at this stage ? Any advice / experiences? Thanks Ross
Unknown at this stage. Probably going to have to take it to 0.010 in the rough then see if its gone. If its not keep oversizing to match your piston availalbity till you get one that works.
Track 73 is deade on right. I watched a guy blind sleeve my nail head once. He got the frozen cyl all in except the last 1 inch or so and it it took about an hour with a 12 lb. hammer and a oak block to get the last bit to come up solid. I raced that engine till the world looked level and it never gave any problem. between the interference fit and the stop at the bottom and the heads bolted on top that sleeve aint going nowhere. I have saved several blocks by sleeving them. none have failed. think about it the block is cast iron, the sleeve is 1/4 in thick steel, much stronger plus backed up by what is left of the cast iron cyl. We are assuming a good machineist here not some goober that can tear up a new anvil with a rubber hammer.
Certainly hang on to the 425 block just in case you want or have to sleeve it one day. There were only roughly 100,000 of the 425 blocks made (vs millions of 401s). The 425s are getting harder and harder to find in any condition. Cheryl
Another mistreated 425 Hi Guys I picked up my second MW code 425 block yesterday....waited patiently for 6 months while it found it's way here from Missouri. It appears standard bore as quoted by the seller but what a mess. :ball:The heads were off it and it is badly corroded in the cylinder bores. Why can't people look after these old engines a bit better? It has 7 frozen pistons. One of the pistons has already been knocked out of the block and whoever did it has missed the piston and hammered the top of the block. The sealing surface around the cylinder has been dented about .035" and mushroomed the cylinder wall as well. :shock: Nasty. Can the top of the block be machined that amount or does the "dent" have to be built up somehow before the block is flattened off? Hopefully the cylinder bores can be saved on this engine without excessive machining or sleeving as these engines ARE getting harder to find, especially in good condition. Any help or advice once again appreciated, thanks. Ross
On a stock 401/425, the pistons are typically 0.045" to 0.060" below the deck surface, so removing 0.035" from the deck should be okay. You do want to have at least 0.035" between the piston and cylinder head on the assembled engine. If you use a 0.015" thick head gasket, it may be close. But if you use a thicker 0.040- 0.045" composition head gasket, you'll have more than enough. There's a neat article on building a '66 GS for NHRA use called 'Building Buicks for action' on www.buickstreet.com They recommended even more of the deck be cut.... so piston is 0.010" below the deck..... :TU:
Hi Walt Thanks for the advice and link. Definitely worth a read. I'll try and get the pistons out and then get the bores cleaned up and measured and see where to from there. Hopefully I will be able to get the big Nailhead sorted and not have to resort to a big block from another GM manufacturer. I think I would return the 322 to the engine bay before that!! Ross
If the pistons are rusted that badly in the bores they are N/G anyway. Do this outside. Put muriatic acid in the cylinder on top & cover the piston. The acid will eat away the aluminum & get rid of some of the rust on the cylinder wall. The piston will be destroyed but then they will come out without harming the cylinder wall are further than it already is.
