Dual Vaccum Dizzy

reifwj · #1 (**permalink**) 05-13-2008, 12:03 PM

I'm cleaning out the garage, ridding my self of the old engine, and found what looks like a dual vaccum dizzy. I believe this is what the 390 had on it before. are there any advantages to the dual vaccum dizzy? Would it be work rebuilding, or should i just junk it?

Bear 45/70 · #2 (**permalink**) 05-13-2008, 12:15 PM

No advantages at all. It was an emissions thing. You can just use the front port or replace the advance unit with a single unit.

Redmanbob · #3 (**permalink**) 05-13-2008, 01:19 PM

This whole dual vac dizzy thing has been on the plate somewhat often right here lately. From reading the posts, is it my imagination or ? Is the main purpose for this style dizzy to coverup the fact that the ported setup was causing overheating issues ? And as a resolution to a simple problem they created a band aid part with extra gizmos to go wrong and require yet more$ to replace/fix. ???????????? Inquiring minds want to know.

Bear 45/70 · #4 (**permalink**) 05-13-2008, 01:25 PM

Quote:

Originally Posted by Redmanbob

This whole dual vac dizzy thing has been on the plate somewhat often right here lately. From reading the posts, is it my imagination or ? Is the main purpose for this style dizzy to coverup the fact that the ported setup was causing overheating issues ? And as a resolution to a simple problem they created a band aid part with extra gizmos to go wrong and require yet more$ to replace/fix. ???????????? Inquiring minds want to know.

Nope, it retarded the timing on decel. to improve emission numbers, NOX if IIRC. Had nothing to do with any heating issues. I have never heard of ported vacuum causing overheat problems if the system was working properly.

Redmanbob · #5 (**permalink**) 05-13-2008, 01:28 PM

? Guess I read those posts wrong ?? could of sworn there was mention of a thermally activated vac unit for the temp issue in traffic.. but then I have read a lot of crap wrong before..

Bear 45/70 · #6 (**permalink**) 05-13-2008, 01:58 PM

Quote:

Originally Posted by Redmanbob

? Guess I read those posts wrong ?? could of sworn there was mention of a thermally activated vac unit for the temp issue in traffic.. but then I have read a lot of crap wrong before..

Different deal all together. My 1984 F250 with a 460 has what you are talking about. Single advance unit with ported vacuum and manifold vacuum to the thermo switch. Normally the ported vacuum runs the advance, but if the engine temp gets above a certain temp, IIRC 210° or 220°, the switch changes the input to manifold vacuum, there by advancing the timing and increasing idle speed to cool the motor down. Only works when you are stuck in traffic or idling a lot in hot weather. No dual diaphragm involved.

Redmanbob · #7 (**permalink**) 05-13-2008, 02:52 PM

ahh!! hmm gets me to thinking as mine heats up while idling. Either a similar part adapted or a manual means of the same thing "That would require me paying attention though" LMAO!

Bear 45/70 · #8 (**permalink**) 05-13-2008, 04:58 PM

Quote:

Originally Posted by Redmanbob

ahh!! hmm gets me to thinking as mine heats up while idling. Either a similar part adapted or a manual means of the same thing "That would require me paying attention though" LMAO!

Either put a "T" where the temp sensor is or find one of the thermostst housings that has the threaded hole for the sensor.