The vacuum advance (delay?) valve

[adam quantrill]

Thought I'd split off this thread to avoid polluting the "idling" one.

Seems there are different explanations even on the same websites:

http://tvr-parts.com/tvr-parts/part-details/tvr-e0...

The wording seems a little odd:
"Vacuum advance delay valve for the Rover V8 . This device acts as a restricter and limits the vacuum being supplied, and, therefore, the amount of timing advance available. Mostly used on the 5.0 engines, it can be a great help in controlling "pinking". Can be used on any of the Rover V8 models as fitted to the V8S Griffith and Chimaera."

https://classicroverforum.net/index.php?threads/va...


and

http://www.britishv8.org/Articles/Curving-Rover-Di...

Maybe it's just there to protect the diaphragm, maybe from front-firing.

[adam quantrill]

RCK974X said:

This unit delays more vacuum advance happening (on) but does NOT delay vacuum drop (off).

So far so good.

RCK974X said:

So therefore right way round is when you can suck air through it without resistance, the end in your mouth should go to throttle ?

No the other way around, if your sucking the throttle end (applying more vacuum) then you should feel resistance.

[adam quantrill]

Try throwing in some octane boost - the castrol valvemaster plus is good. Works out at 3p/l which is cheaper than the difference between 95 and 98 RON.