I have one of those wonderful factory intakes on my 12,000 lb. GVW B300 that has a million vacuum hoses for various emission junk, even though it's a 1973 (DOM 1972 on the engine itself), and most appears to be for venting the gas tank WAY in the back of the rig.

How much of that crap do I really need just to vent the tank so the fuel system operates properly? Can I simply use the vacuum advance, the power brakes, and the choke pull-off, and leave all the rest of the stuff for the rubbish pile? Yes, it has a charcoal canister system, but no air pumps, and that sort of thing.

Depends on your emission laws, but I think alot of the hoses and thermal vacuum switches are for the EGR control. On my truck I disconnected all the hoses to the vacuum canister and EGR.

We were testing back to 1968, but that JUST changed this month to 1997 (or something like that). Besides, GVW over a certain weight is exempt from testing.

I want remove all of that head-ache of vacuum mess, but what do I need to leave there for the HUGE tank to vent properly?

EGR (if there is one, I'll look because I don't recall) and all that krap is going away. Might even be changing to a 4V set-up before I'm done, and I don't want to have solve the vacuum line puzzle.

I just left the charcol canister. If you have a mighty-vac tester, connect it to the canister where the vent line will go to verify it will vent (not pull vacuum.)

I do have a Mity Vac (who doesn't?) and that is a great tip! Thanks!