Has anyone done the conversion from a vacuum retard to vacuum advance distributor? Sounds like a good idea to me (my vacuum to the distributor has long been disconnected). Seems like an easy conversion while talking with Rob from British Vacuum Unit. Any thoughts or comments out there?
Thanks in advance !
Ralph
'72 S3
Hi Ralph, I am in the middle of doing this, and I posted a few months ago about my rebuild of the advance ( and retard ) modules to put in new diaphragms. Just about to replace one of the carbs with one drilled out to supply vacuum to the advance module .
Topic was S!!! Dizzy Conversion March 11 2018
John, it’s your post that got me to investigate. BVU supplies an advance unit for the original V12 distributor and will modify one of my carbs to have the correct vacuum port for it. I was wondering if there are others out there that have done this and what their success/opinions were.
Ralph
By the way,I have checked my 1973 strommies, and lo and behold the port is already drilled on my 1973.That port was used on the 1974 XJ12 saloons for the EGR port.But it is exactly the same position as the one we need. It’s possible that yr 1972s have the port drilled. Mine, which was not used on the 1973 had a 7/16x20 grub screw as a plug.( actually there were 2, one atop the other ).Please let us know how you get on, and good luck.
John would you be able to send or attach a photo of that port showing it’s location?
Thanks !
Ralph, Sorry can’t photo the port ( the carb is on the engine! ).Its position is just to the side of the butterfly valve while at rest…so that when the butterfly valve even starts to open, the port sees the vacuum.Then as the valve opens further the vacuum decreases.Take a look at .Paul's Daimler Diary, my Classic Double Six Vanden Plas, repairs, modifications, and photo galleries. to see exactly what i mean ! Regards, J
I see his photo http://www.pclarkson.plus.com/pages/carbrad2_JPG.htm mine does not have this port. This is where BVU will machine one in for me.
Hello Ralph,
As you have no doubt discovered, your Strombergs have the lug where the port is shown in the picture, but no hole. Cars fitted with the full blown emission control hardware had a plain hole in this lug into which a link pipe was assembled and continued down to a threaded fitting in the top of the exhaust header.
Regards,
Bill
On my 1971 S3 I have tried the original distributor retard, changing the dizzy vacuum unit to an advance, and disconnecting the vacuum unit. I didn’t see much difference in performance so went back to the retard for concours judging purposes. I’m interested in your results with the advance unit.
Hopefully I’ll be getting to this before the end of July. I’ll post the results.
Hi Fenner, The vacuum applied at the correct time to actuate the advance unit is important. It is needed only at low throttle settings, and is usually generated by a port in the carb close to the closed butterfly .You don’t say how the vacuum was generated ?