Posted by Chris Case [172.69.33.19] on Friday, April 28, 2023 at 15:30:06 :
1/2" aluminum. Cut with a hole saw. Or maybe saw on a wood cutting band saw, make it octagonal so the coolant can flow around it to the overflow tube. Looks like I used a die grinder to cut a channel around the OD, probably not necessary. Plus cut a cork gasket/washer to seal adapter to bottom of filler neck.
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