1940 Flathead, bored from the original 3-1/16 to 3-3/16, (239ci). In the 2nd cylinder from the front, the previous machine shop must've found the crack between the water jacket and the cylinder. So they sleeved it to save the cylinder. Here's the crack (Yes, there is also the crack from the water port to the head stud, that one isn't as critical: Due to the condition of the inner sleeve, my machine shop would like to replace the sleeve with a new one, but they're concerned about this: The prior machine shop bored all the way through so it's a floating sleeve, not seated on a step in the bottom like most of the industry does it. My questions, is that crack something I should be worried about? Is there any concern about a floating sleeve in a flathead that's not going to be raced or run under extreme conditions? I have a backup engine I could go to, but this one is super clean other than this issue. Please let me know your thoughts. ~Peter
With my no shop experience-I would think it will be good if it is anchored up on top. It should expand with heat and lock in nice and tight if it isnt already. Or they may have to open the bore up and do the step if they can. My 2 cents worth. Mike
I wish there would be a little more discussion of this. To me that looks like something to put together and run.
Decking the block could alleviate the crack . Some of us call it a Stepped Sleeve and my machinist uses these exclusively and are alot pricier of course but rigidity is BarNone . One guy with a shop claims he step sleeved all 8 cylinders so his block is stronger . I don't know about that may be wishful thinking 3 block trusses are only as sturdy as 3
That's my leaning at the moment. Considering I'm not going to be racing or supercharging, I'd expect cylinder temps and pressures to remain pretty consistent. ~Peter
What’s the problem with the sleeve ? Is it worn very badly ? Why not do a good hone and new pistons and run it ,,,,,like Leon Bee thinks ? Tommy
40 years ago in an O.T. situation, a 4 cyl. BMW 1600 block was to be bored out then sleeved back to 1800 cc. Factory engineer rep said "No, No!" Technical Factory studies had blocks 'growing' in length from pressing o/s sleeves in, (all 4) Raised my eyebrows...
Boring all the way through is a lot easier than putting a step in it and it was pretty much standard operating procedure for most production shops. If the interference fit between the block and sleeve is correct it shouldn’t go anywhere. I’ve seen many engines that had many miles logged and race engines that never had a problem. I’ve never done it cause it just doesn’t feel rite. I always stepped it like mentioned. And I’ve sleeved a few flattest with that same crack situation. I used the lock-n-s***ch sealant on the sleeve and never had a problem. I’m also curious as to what the shop doesn’t like about the sleeve. Oh and I always pressure tested and payed close attention to the bottom of the sleeve. Especially if it got into the water jacket.
We suspect when the previous shop pressed in the sleeve, they scored the cylinder wall badly. So when they bored it back to 3-3/16, they ended up going past a little to try and get rid of the damage. So it's already at the very edge of the tolerance for the rings. My shop says if they were to hone it, it might still have some leak-by from those gouged areas, and of course, then my diameter would be out of spec and my rings would have to be left super fat to get them to seat properly. I'm going to get some better numbers and explanation tomorrow. I'm not a machinist, so a lot of this is new to me. ~Peter
Ya and Alice grew to be 10 ft tall ! Those silly Reps always good for a laugh , I also recall that our Euro blocks we heated up on a BBQ and had a feast while our manager slammed them in with a sledgehammer most were Benz blocks
True they should have offered him a pressure test I think it's 20 lbs everyone is using for a given time I'm guessing 2-4 hrs some probably do it in 15 minutes . He can probably run it with a good coolant sealer also like the coolant pellets or discs Cadillac offers for the Northstar equipped engines . Now he knows to go with stepped sleeves next time . I'd seal it up and run it I don't think an Iron plug kit will help him I question a plugs ability to seal on the sleeve it ain't cast those plugs are for cast . I think decking will give it a better chance and the bottom seal it there is rust marks looking fresh on the bottom side in the pictures too so yes he should pressure test this or start with just filling up the lower jacket with water and let it sit if more rust shows up well you have a leak . It's worth a try for a simple start . Now I'm editing because I should also mention that the rust marks at the lower sleeve edge could be the block emitting moisture due to the blocks ability to hold moisture for years . The flathead block I am currently preparing is emitting trapped moisture now that I have it bare of oils and sitting in the open under the bench . Example is I ported the valve bowl area and 4 days later there appeared a wisp of rust out of nowhere and other bowls are still shiny . I could blah blah the science but ain't going to change what is happening I just hope that the block on this thread is emitting trapped moisture without damage to it
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