Oil + additive viscosity

Ok. Yes thats is what is in the filter bracket. But mine does not have the tube. They are flush mount since the filter does not hang. It sits upside down. Inside where the check valve is the diameter is 5/16". The one on the car is actually from a slant six and I have cut the tube off. I am using this because the thread is AF to suit a Z9 filter. Originally the filters on the v8's came with a Z96 filter which is half the size and has a metric thread. The pic of the thread on the radiator cap is the original one which was installed in the bracket. Both have the check valve in them.

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