Re: Need to repair cylinder bore ID on alloy block

Posted by D. Novotny ( on 17:54:12 18/02/06

In Reply to: Need to repair cylinder bore ID on alloy block posted by Erik Berg

Aluminum blocks have been welded quite successfully - drag and endurance racers do it quite often - in the USA. However, the process involves careful preheating, welding, thermal management while welding and post weld stress relieving and re-heat treating in some cases.
HOwever, depending on the severity of the weld/damage, it may cost more to weld and requalify the machine surfaces to straighten things out than the block is worth.

Moreover, if you've welded up what was a water jacket between the bores, localized overheating could be a lingering problem.
In the long run, you may be better off simply boring out the alloy, fitting in an aluminum tube/sleeve and welding the top and bottom. THis would preserve the cooling jacket integrity much better than than merely ladeling in a bunch of weld and dealing with same.
By the way and more importantly, lock ring failures (root cause of your problem) are caused by shutting down an overheated engine without benefit of cool off lap, too tight an endplay of the pin to lock rings and/or bent con rod.

The first two conditions cause the aluminum piston to shrink down faster over hot steel pin shoving out lock ring - latter condition is caused by poor inspection and/or hydraulic lock.
In some instances, improper assembly techiques can cause the lock rings to break but usually it is the items mentioned above...

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