Was speaking to a custom bike builder about 6 months ago who have used the S&S motor as the basis of many of their builds since the motor was introduced about 10 years ago. I asked if they have any issues with cam belt failure and he indicated there was a period when S&S had an issue due to the drive gear (on the crank) and idlers, but that has since been corrected. When I asked about heat related issues with the cam belts he seemed genuinely puzzled as their high performance street machines have never seen anything like that, and they have much less airflow over the cover due to the engine position in a motorcycle chassis. When I told him about the Morgan recommended practice of adding spacers to the cover, he thought that was a very bad idea as sand/grit in the cam belt would be much more worrisome than excess heat.
I followed up with correspondence directly to S&S about the availability of a vented cover to preclude heat induced cam belt failure, and was told they do not make such a thing because it is not required. They did indicate past issues with cam drive/idler design and a batch of cam belts not made to spec. They also advised against cam cover spacers to avoid debris in the cam belt area.
Not knowing whom/what to believe, I removed the spacers which the PO had installed, as the practice of using spacers on a cover the original designers had deemed worthy of a gasket did seem silly to me, and I then drilled some holes and added covers to allow heat venting without grit ingress. So still not sure where the facts lie, but I feel better.
Bottom of cover:
Top of cover with small stainless covers over drilled vent holes:
