1960s 1961 brake booster vacuum line 3/8 or 5/16?

[dbzsjones]

I thought this would be easy.  I looked at the old hoses and measured the nipples on the vacuum tank and brake booster and got .375" so 3/8".


Off to the parts store and pick up some hose and transfer over the spring clamps and wire clip.


Everything looks good and fits, but then I slide it on the nipples and it's too large and won't hold vacuum. I can crank it down with worm clamps and get it to seal, but I was hoping to stick with the original clamps.

I decided to try 5/16" and picked up some silicone vacuum line and it fits snug and seals without any clamps, but it's to narrow for the wire clips, and being silicone it's too shiny.


Has anybody else run into this?
Any recommendations?
I'm guessing all the hoses are actually metric these days and 3/8 isn't true to its size and it's a metric approximation.