442
Why are you playing with your friend's car?
Sorry had to ask.
Some Holleys have an adjustment screw to stop the secondaries from shutting completely. Maybe the secondaries are open a bit which is allowing too much air to pass the carb at idle. It is a small screw that is not easy to see unless the carb is on the bench.
By the way, why didn't your friend pull onto the shoulder when his engine began to over heat?
Wayne