Vacuum delay valve

V

V8P6B

Member
Hi all,
I was having an interesting chat last night with a guy who used to tune cars, and we were talking about the problems with modern fuel etc, and the need to retard the timing to stop pinking. He said the problem with retarding the ignition timing towards TDC is that it make the performance a bit flat. He reckons you can sort out some of the problem by fitting a vacuum delay valve in the vac advance pipe, which would delay the vac advance and reduce pinking. He says it prevents the vac advance from getting any vacuum until there is a lot of vacuum, ie under hard acceleration, and therefore help reduce pinking. Don't fully understand what he was on about, but he seemed very technically knowledgable. Is he talking cr*p, or is there mileage in it?
 
If he was a proper engine 'tuner', I'd have thought he'd do it properly by putting new springs and a cam in the dizzy, changing the vac unit and re-needling the carbs.
It might have worked on a handful of cars he'd done, but it's a bit of a botch, and as a solution not a particularly intelligent one.
Pinking is just fuel igniting too early, either because there's too little of it in certain conditions, or because the spark plug fires too soon. The only real solution is to put new needles with a more appropriate profile in the carbs, to get the right amount of fuel in at all revs/loads. And remap the distributor advance curve to get the bang in a better place every time.
It's not very difficult in theory, it's just hard to achieve in the real world without specialist assistance. Which is why I'd be a bit worried when even the specialist says stick a bodge in to faff it into working...

Michael
 
Well, that was kinda my thoughts too. We were having one of those theoretical chats over a few beers, and I came to the conclusion he liked the sound of his own voice. :roll: I thought I'd bounce the idea on here though, as it sounded mildly intriguing. I must admit, although I get the basics of how stuff works, I'm no expert, so I thought I'd ask.. :)
 
Another error that this fellow made was that under hard acceleration, engine vacuum drop considerably, so that in terms of ignition timing and vacuum advance, there is essentially none.

Engine vacuum is only available for timing advancement under very light throttle settings, that is where the pedal is almost hardly touched. Crusing down the freeway being one such example.

Micheal is spot on when he says that having the distributor regraphed is the right way to go about sorting out engine pinging, in combination with needles that are correct for the engine. Just as running needles which are too lean will promote pinging, so running needles which are too rich will expediate engine wear.

Ron.
 
Didn't Ford put valves like this on Escorts Sierra's etc in the 80's ?
Not saying that doesn't mean it's a bodge !
 
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