Ported vs manifold vacuum for dissy
 

I have modified the vacuum feed to my dissy from the ported vacuum port on the carb to direct manifold vacuum.

This I did to derive the benefits of full vacuum advance at idle - like I have done on all my cars over which I have this kind of control.

Main benefits:
1) more efficient idle, hence;
2) lower idle fuel consumption (academic I know);
3) less heat being generated for cooling system to get rid of (not an issue on the 235, but a very substantial issue on my V12 Jag, and the 440s in my Jensens .)

Re: Ported vs manifold vacuum for dissy
 

Thanks, that question comes up regularly.

Re: Ported vs manifold vacuum for dissy
 

Good idea. Here is a longer explanation http://www.superchevy.com/how-to/add...nition-timing/

Re: Ported vs manifold vacuum for dissy
 

Actually the majority of pre smog control engines with carbs used manifold vacuum on the advance anyhow. That is why the first step of setting the timing is to pull the hose off and plug it to run without vacuum advance to set the timing.