I Had been using this stuff http://www.kleenflo.com/products/651-652-653.html but it is no longer available in Canada. Not sure about the US. Worked great but Pretty nasty stuff!!!
Now using this in my ultrasonic cleaner. https://gunk.com/product/gunk-hydro-seal-ii-heavy-duty-parts-cleaner-hs3c/ Not as good, and not as nasty!!!

Jim

1970 Superbird 440-6bbl, auto
1969 Barracuda 340-4bbl, FB Formula S auto
1969 Barracuda 6.1 L Hemi, 5 speed, Convertible
2022 Can Am Spyder RTL