78 Suburban bogs then dies on long grade

[RyanAK]

Things got better with the new fuel pump. Also sprayed down the carb really good and dumped a can of Sea Foam in the tank. Seemed to run much better and haven’t been able to reproduce the bog. But it’s been relatively cool here.

I also replaced springs and weights in the distributor and set timing. More improvement.

The biggest improvement came when I moved the vac advance to straight manifold vacuum. This truck has a temperature vacuum switch (TVS) that changes the vac advance between ported and manifold based on engine coolant temp. I couldn’t confirm it is working properly, so hooked up to straight manifold vacuum. Seems much more responsive.

If the TVS was wonky and basically eliminated the vacuum to the vac advance can, could that have caused the surging and bogging I experienced?