Thread: Engine options
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Old 07-20-2017, 11:05 AM
pbf777 pbf777 is offline
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Originally Posted by Wyldie
Cylinder 6 however has a broken ring which has damaged the bore. Just my luck! Anywho hoping someone can tell me what's the maximum I can bore the block to? What are my options?
Unfortunately, the question of what the maximum amount of material, that can be remove to achieve a required bore diameter with in a particular block, and maintaining a reasonable service life, isn't so simple to answer accurately.

I am of the general opinion that the highly educated and therefore well paid engineers were tasked with the responsibility of creating a product (engine block) that would provide acceptable service life, under the environmental conditions in which outlined, and maintaining costs of manufacturing to a minimum. With these parameters in mind, add the fact that the FE engine was of Ford's newly announced "Thin-Wall-Casting" technique, and the understanding that Ford Motor Company wants to sell new vehicles, not have you rebuilding your old one; why would anyone assume that there is any additional, unnecessary material (iron) added, over and above that required to keep the vehicle out of warranty claims and allow the targeted cycle life by the manufacturer?

Does this mean one can't bore a block to an oversize in the rebuilding process, no, it is practiced; but remember, all things practiced, even if it "works", are not always necessarily correct. I believe this allowance is due to the engineers consideration for manufacturing tolerances and given inaccuracies. Such variables exist in the metallurgy, pouring and casting technique, finish machining, etc.; these considerations cause the addition of materials in order to reduce rejections.

I believe the best advice is to always remove the minimal sum of material from the cylinder walls as possible for best results.

In a more direct answer to your question, if the damage (scoring) in the cylinder will not "clean-up" in reasonable honing, then one would advise a repair sleeve installation process.

"Reasonable Honing", well your block has already been bored .050" oversize (what is required for the other cylinders?); I suppose one could explore out to .060" (check for ring availability), but that's where I would draw the line. And I didn't say that such is an acceptable "maximum", it's just often practiced.

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