Thermal Vacuum Switch Post Engine Swap

[Bruce Wingate]

The PO put in a "new" "crate" engine in my 1984 K10. It runs a little rich but starts and goes just fine.

It is my understanding that the thermal vacuum switch can be disconnected with a SBC and an HEI distributor. Looking at this picture, it looks like the vacuum source for the distributor is not hooked to anything. ( I know the wiring is a mess, I'm working on it)

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So: 1) can i just hook up the advance can to manifold advance? (and remove the vacuum switch?)
2) Do the wires from the vacuum switch go directly down to the temp sensor in the head?

Thanks,
Bruce.

 

[Bextreme04]

The PO put in a "new" "crate" engine in my 1984 K10. It runs a little rich but starts and goes just fine.

It is my understanding that the thermal vacuum switch can be disconnected with a SBC and an HEI distributor. Looking at this picture, it looks like the vacuum source for the distributor is not hooked to anything. ( I know the wiring is a mess, I'm working on it)

You must be registered for see images attach

So: 1) can i just hook up the advance can to manifold advance? (and remove the vacuum switch?)
2) Do the wires from the vacuum switch go directly down to the temp sensor in the head?

Thanks,
Bruce.

That's not a TVS. A TVS would be threaded into the water jacket in the intake manifold and would switch the vacuum ports when the engine warms up. That is likely a tip-in switch, was the original engine a 305 in your truck? The tip-in switch would go to the ESC controller on a 305 so that it retards the timing a bit when you go full throttle to prevent detonation. On a crate 350 with a non-esc distributor, it shouldn't be doing anything.

You should have the vacuum advance can running to the manifold vacuum port on the quadrajet. It will be the small vacuum port on the drivers side front of the carb. It looks like it goes up to a T on the tip-in switch and that line is unplugged and sitting on top of the carb in your pic. It might have been connected to the large manifold vacuum port screwed into the intake manifold in between the carb and the distributor originally. That is not the right place to connect the vacuum advance and will make it very hard to set timing and idle mixture since you need to disconnect and plug that line when setting those things.

 

[Bruce Wingate]

Thanks - I don't know where it was originally hooked up to. Vacuum lines on this thing seem to be randomly used or ignored. The engine swap seems good mechanically but the details were kind of ignored.

I have to check to see what the original engine was - I just assumed it was a 350 but evidence is pointing to a 305. I put the vacuum line up on the carb to show it was disconnected.