The Ford Barn - View Single Post - Manifold vacuum at idle... vs without...interesting observations

Hal Beatty · 01-19-2021, 04:33 PM

OK, so this discussion has raised my curiosity and I went out and grabbed a couple of non-Ford carb/intakes off the shelf. First one was the stock intake from a '62 Cad with the steel vacuum line still attached; traced the circuit in the 4GC base and

it comes out below the throttle blades, manifold vacuum.

Then grabbed the set-up off of a '54 Cad, traced the vacuum passage and it comes out above the throttle blades, ported vacuum. So some variation here...

I'm not debating the merits of ported vs. manifold vacuum advance here, every engine is different and you'll have to experiment with it. Just the idea that ported vacuum didn't appear until smog controls...

01-19-2021, 04:33 PM	#29
Hal Beatty Senior Member Join Date: Jul 2012 Location: Bellingham, WA Posts: 213	Re: Manifold vacuum at idle... vs without...interesting observations OK, so this discussion has raised my curiosity and I went out and grabbed a couple of non-Ford carb/intakes off the shelf. First one was the stock intake from a '62 Cad with the steel vacuum line still attached; traced the circuit in the 4GC base and it comes out below the throttle blades, manifold vacuum. Then grabbed the set-up off of a '54 Cad, traced the vacuum passage and it comes out above the throttle blades, ported vacuum. So some variation here... I'm not debating the merits of ported vs. manifold vacuum advance here, every engine is different and you'll have to experiment with it. Just the idea that ported vacuum didn't appear until smog controls...