• From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,586

Topic: vacuum advance cutoff ???

I'm working on restoring a '73 bus and found a couple of unfamiliar parts. Found them on page 73 of the Bentley. It's a temp sensor and vacuum cut off that cuts off the vac advance in all gears except 4th when the temp is over 12'C (54'F)

Why??

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Registered: 2009-06-25
  • Posts: 554

Re: vacuum advance cutoff ???

I'm sure someone who is more of an expert will chime in eventually, but there are a couple of reasons that I can think of: One would be to eliminate detonation at slower speeds like around town and in heavy traffic, while still providing full advance when on the open road in top gear. This would also allow more initial advance at low RPM without going into detonation. Another reason could be for emissions, even though I don't know what loophole they would use for allowing full advance in top gear or when the temps are low.

Just my 2 cents, but you might need a refund when an expert steps in, lol.

Paul

  • From: Fort St John BC
  • Registered: 2006-10-06
  • Posts: 8

Re: vacuum advance cutoff ???

I would like to hear the answer to this one as well.  I just did a quick go over on the enigne on my 73 westy and I'm about to put it back in .  I was just reading about this switch in the manual.  I was thinking of taking it out, but i will wait and see where this thread goes.  Was this a 73 model thing or was it on others?  I have a 72  in my junker bus collection and it doesn't have this switch.

Trevor

  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,586

Re: vacuum advance cutoff ???

I am working on a '74 as well that doesn't have it. I think it's an ineffective pollution device that is probably better left off.

jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Registered: 2009-06-25
  • Posts: 554

Re: vacuum advance cutoff ???

jamesdagg wrote:

I am working on a '74 as well that doesn't have it. I think it's an ineffective pollution device that is probably better left off.

jim

I'm kinda leaning that way too.