xlh59 wrote:Hi All,
I am also considering to resleeve on of my cylinders as it would need a 0.06 oversize piston while the other cylinder is fone with 0.02 -- so let me repeat Hennesse´s question: whats the downside of resleeving the calinder?
Nothing. See below.
xlh59 wrote:I also have found a hairline crack between one intake and the cylinder bore -- basically exactly like the described one. I went to my engine expert (who is specialized on flathead engines) and he told me "dont touch it" ? The brazing solutions seems fine to me (from an metallurgical point of view) but then I would need to install a new seat?
Both sleeving and braze welding have been used successfully for more than half a century to address the situation you describe. I don’t know what your specific project looks like (the nature of the crack and the larger overbore cylinder), but as your mechanic noted, the crack described may not even be an issue. K Models are strange in this regard as many heads and cylinders exhibit apparent “cracks”, yet these cracks never grow and tend be more superficial than structural deficiencies.
My suggestion regarding avoiding sleeving is simply one man’s opinion (mine) on the matter and does not take into account the myriad extenuating circumstances that may be relevant to the specific situation such as you describe (mismatched bores) and as mentioned above.
If a “real” leaky crack exists in the cylinder I like braze welding as a first remedy because it is a robust solution that leaves the cylinder fully intact and requires only the installation of a seat to resolve the issue. If I need a sleeve at some point in the future when the bore is too large it can always be installed then.
Sleeving is likewise a robust solution and has a few other
minor attendant considerations. The structural integrity of the cylinder is strongest as-cast and machined, and every bore job thereafter weakens it slightly (the reason we don’t like to go much over 0.060” OS, with sleeve installation being the largest over-bore it will ever see). Because the sleeve does not make intimate contact with the cylinder (both cylinder bore and sleeve are machined surfaces and therefore an extra interface [sleeve to cylinder] is interposed between the heat source [the bore] and the cooling source [the fins]), the efficiency of heat transfer will be higher with the virgin cylinder than with a sleeved cylinder.
As mentioned at the outset both braze welding and sleeving are satisfactory solutions for your issue and will work fine. My rationale for favoring the braze weld over sleeving is given above. I’m not at all averse to sleeving, just not my first choice as I’d save sleeving for somewhere down the road when the bore is used up. My $0.02. And remember, you get what you pay for and $0.02 worth of advice may not be worth taking.