View Single Post
JFairman JFairman is offline
Registered User
Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Originally Posted by 9dreizig View Post
Got the engine on the stand today, getting ready to clean it up and figure out where the vacuum leak has been all these months..
So here's what I found.. Since I"ve ripped the air pump and CAT off this.. Do I need this ? It's the thermal switch
Like everyone has said, you don't need it unless you have to have all the emission crap working perfectly, and the car will run better without it because you'll have vacuum advance to give the motor a little more pep as soon as you start it cold.

Don't just bypass the goofy thing, replace the entire red vacuum line because that origonal cloth braided vacuum hose dryrots and cracks under the fabric surface and you get a vacuum leak that is impossible to see and harder to diagnose.
The origonal vacuum advance hose was red and the vacuum retard hose was a dark blue.

The purpose of that little mechanical temp switch was to block vacuum advance to the distributor vacuum advance pot during cold starts and for a little while after a cold start until heat transferred up to it - opening it and letting vacuum pass through.
That would leave the distributor with centrifical advance only so that would retard the ignition timing enough to raise exhaust temperature because then the gas is still burning a little when the exhaust valve opens and the higher exhaust temp heated up the catalytic converter faster so it would lower emissions sooner.

There were 2 electrical vacuum solenoid switches too.
One would block vacuum retard to the vacuum retard side of the distributor vacuum pot for about 1-2 minutes after a cold start so the idle would raise about 300 rpms and not stall out with all the other emission crap and lame timing settings dogging down the motor.

The other vacuum solenoid just to the left of it was wired in parallel and was plumbed to trigger manifold vacuum to the left and right side air pump diverter valves so air pump air flow would switch from the exhaust ports to the catalytic converter.

yeah i know, more than you wanted to know... but maybe it will help someone.
Old 08-22-2010, 09:02 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)