View Single Post
Old 03-18-2021, 09:13 PM   #5
Steeveedee
Who Changed This?
 
Steeveedee's Avatar
 
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,950
Re: What are these ?

Quote:
Originally Posted by ChevyGuyNC View Post
Thanks! I'm going to keep it bypassed.

At the risk of starting an argument, From the distributor advance to manifold or ported vacuum? I've read in other threads that there was a switch from manifold to ported as a band aid to reduce emissions...
There was a thermal switch on the thermostat housing and an electrical switch on the transmission for the TCS system. Once the engine was warm enough, the thermal switch would allow vacuum, but the switch on the transmission would not enable vacuum until in high gear (3rd for an automatic, 3rd or 4th for a manual). I think that it was also ported, but it's been a long time since I worked on those. The solenoid on the intake manifold depended on the switch on the transmission providing ground to engage and allow vacuum to the distributor. If anyone wants to argue ported/non-ported, that's on them.
__________________
~Steven

'70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper

Simi Valley, CA
Steeveedee is online now   Reply With Quote