Thread Inserts Compatible w/ Aluminum

[J Tiers]

I have used stainless heli-coils in aluminum cylinder heads without problems. Spark plug holes.

Yep, some are still fine 25 years later, because I still have the piece of equipment.

[old mart]

Back in the 60's, with British motorcycles, bought some coils made by Cross Manufacturing, as they worked out slightly cheaper than Armstrongs Helicoils. I could only afford 3 sizes, 1/4", 5/16" and 3/8" BSF and the coils were carbon steel, not stainless. They came in very useful and could be fitted with only home made tools, and I bought 2d lengths as it was easy to shorten the coils if necessary. After all these years, I still have the taps and some coils which are identical in dimensions as the Armstrong products.
Since cad plating is toxic, it is not surprising that the Helicoils used for aircraft not generally available to the public.

[Mike Burch]

If the damaged hole is a through-hole, you could drill it out slightly and fit an aluminium rivnut. Then there's no problems with corrosion.

I have no experience of fitting rivnuts in blind holes, so I can't say whether that would work or not.