Intake Manifold Oil Leak

I have a KB with Veney heads.
I am having problems sealing the front manifold valley. I am using a spacer with soft manifold end strips and sealant. I sealed it several times but with no luck (rear seals fine).
A saw a picture a while back with someone using a piece of thin alloy shaped as a "Z". This plate was to be put in the valley
Has anyone got details on how this works ie size, which way up, where to seal etc

Thanks for your help

Cheers Neil