MSD 8360 distributor vacuum advance

Ever since putting 2.02 camel humps on my 350, as I am cruising there is a slight surging in the engine. If I put my foot in it to give it load it is smooth as can be. Have done many different timing settings it is always the same reaction, I even put on a new vacuum canister. However, if I do not connect the vacuum advance the engine runs smoothly at any throttle setting, as soon as I hook up the vac canister it will surge. And yes, I have looked everywhere for a vac leak but I find nothing. Really stumped, but I think it has to be a simple solution.

Not sure on the MSD Distributor, but most of the old school factory vacuum advance units could be tailored for the amount of vacuum required to start moving the advance arm. The adjustment was thru the vacuum nipple with a small (but long) allen wrench. A little more (or possibly less) spring pressure may do the trick. There's probably a video or 2 on You Tube about it.


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Welcome to CHR.
I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed compared to WOT. Getting this mixture to burn completely takes more timing. I think you're getting surge because of unequal burn between cylinders. Here's a really good explanation of vacuum advance - (link)

https://www.onallcylinders.com/2015/...y-you-need-it/