I have a stock 1957 Ford distributor with a Pertronix unit in my 292.  I would like to replace it with a full centrifugal advance distributor with an adjustable advance curve.  Did anyone ever make such a thing?   What are my options?

For regular street use, doesn't removing the vacuum advance tend to hurt fuel economy?.. 


Paul

Thanks for the input.  My TBird currently has a stock 1957 passenger car distributor.  The only modifications are a Pertronix Unit and lighter Mr. Gasket springs in the centrifugal advance.  My vacuum canister is new and functioning.  I set my timing with a degree timing light at 36 degrees full advance with the vacuum disconnected.  My car seems to respond better with the vacuum line connected.  My car does not ping and pulls strong for what it is. I am happy with the performance, but I am always looking for ways to improve it.

I have had a lot of hot rods in my day.  I'm old school and have never used a vacuum advance distributor. I always considered vacuum advance distributors as low performance.   All my Hipo Fords used either stock full centrifugal advance or aftermarket distributors.  When I put a timing light on my engine and watch the pointer, the timing mark does not advance quick enough.  It seems to lag compared to my previous experience with Ford distributors.  I'm trying to get all the advance in by 3,000 rpm.  Years ago, this could be remedied by a quick run down to the machine shop.  No one has a distributor machine these days.  Should I leave well enough alone or is there performance to be gained here?

There are a LOT of misconceptions bandied about vacuum advance, which stems from the fact it is generally so poorly understood, even by those who should probably know better.

It might be considered "low performance" by some from the standpoint that drag racing application distributors don't even include it. Performance engines aren't driven on the street, these engines are intended to operate exclusively at wide open throttle, consequently the vacuum advance mechanism itself is simply another potential failure point. Since it isn't ever going to be operational, it isn't needed, therefore it isn't used. See the difference?

But vacuum advance has nothing to do with inhibiting or retarding performance as such, because there is no affect at all if it is working correctly i.e. no diaphragm leaks, advance plate sticking etc. Another source of confusion is the terminology itself. "Total Timing" numbers often discussed, does not include vacuum advance. Sounds strange, but it's true.

For street driving, part throttle operation, and cruising on flat ground especially, there is no practical way to achieve the optimum necessary ignition timing advance with mechanical centrifugal weights and springs alone. That's why vacuum advance was invented in the first place. The proper "curve" is not possible.

Estimates vary, though there is somewhere around a 3 to 4 hwy mpg economy loss without it. Engines have better all around driveability and run significantly cooler. I found my Y likes about 52° BTDC cruising. Now this isn't an exact figure because it is measured in the garage, in neutral, with no load on the engine. Vacuum advance is inherently a load operated device. So far though, I've been unable to find anyone willing to sit in the engine bay with a timing light to check it out on the highway at speed.

The Shop Manual shows somewhere around 45° BTDC - total + vacuum advance using a distributor machine if everything is added up - keep in mind OEM numbers are always listed in distributor degrees - not crankshaft degrees - and most Ys had an initial timing of only 3° or 6°.

Short answer: "Yes you want vacuum advance". Nod your head yes.

Something around 50 sounds right for me for light highway cruising.
I tried 55 but it was quite high for stock Y.

Even Hollow Heads dragster got cruising area in the spark map. It may never use it but wont hurt a bit.


Hyvinkää, FI

Leave it alone.



"FREE SAMPLE"

So far though, I've been unable to find anyone willing to sit in the engine bay with a timing light to check it out on the highway at speed.

... hmmph ...

Can we stop at DAIRY QUEEN afterwards  ...

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