I cannot imagine very much oil in the cooler. I completely believe layback4o on this.
1. The cooler does not hold that much. not much of a tank on each end and those cooling tubes are pretty small. It is mostly air.
2. from my 115 days I used to drain mine and there just was not much there.

It is not a bad thing conceptually but in reality, again, I would not risk failure of my fabrication.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.