Technical Vacuum Advance Poll

What say you ?

 

The engine I have been ruining didn't come with one from the factory.

 

When connecting that hose can add 5 MPG to your mileage, why wouldn't you?

 

Depends....

 

I always time with a vacuum gauge, but on occasion when I double check it with a timing light, it always SEEMS closer to my timing mark when the vac. advance is off a carb port, rather than the manifold. I could be just imagining things here...but that's the way it seems

 

Since I'm running a 8BA with a Loadamatic Distributor and the matched 94, if I want any advance at all I have to connect to the carburetor port.
LOM distributors are vacuum advance only.

 

Most always connect to manifold source. Idle & mpg better, and have fixed a few running hot "impossible" to fix. Only a track engine would not use vacuum advance.

 

In general, full manifold vacuum advance will produce cooler idling and better mileage by adding advance under low load conditions.

 

Correct answer , too many different scenarios . AFA 5mpg , I've be very surprised , most situations in reality is closer to 1to1.5 mpg (10%).......yes ,I spoke with Mallory about this 20 years ago , being that it was potentially beneficial to them to sell me a new distributor to improve mileage had their answer been different , 2 different calls with 2 different people at mallory netted the 10% figure ...

 

Ported is the best if you have the skills to properly adjust idle mixture circuits and idle screws on a street engine.

Ported vacuum is similar to having the vacuum disconnected while the running on the idle circuits, but having full manifold vacuum while driving.

When an engine is idling , you want the idle screws as low as possible and the engine vacuum as high as possible [set by mixture, not by advance]

The last thing an engine needs is to be too far advanced while idling [from vacuum advance] then it suddenly transitions into load when the throttle is quickly applied [just off idle]

I hear people say the engine runs smoother idling [or it picks up rpm] with full manifold vacuum.
This is usually DIYers with poor tuning skills.

This ^^^ is all a moot point, if the engine is an over-cammed street pretender with poor vacuum.

 

I've posted this a couple of times but it has a lot of good info
https://www.jalopyjournal.com/forum/threads/vac-advance-or-not.706544/#post-7858834

 

Really ?
One perfect answer for everyone..!

NOT GONNA happen.

Mike

 

Full centrifugal ...

 

Ya, there is no one correct answer. On my 63 390 6V I experimented quite a bit and finally I took off the center carb and drilled the base plate so I could have a good ported vacuum source for the distributor advance. I've been quite happy with the performance since then. Fuel mileage was never that much of a consideration.

 

This thread is supposed to be a poll only, but I can’t let this ^^^ slide.
If you drilled carb base plate (below throttle blades) you got full vacuum, not ported !

Yes, there is one correct answer for overwhelming majority of internal combustion gasoline engines !

 

Ooo do tell, the suspense is killing me!

 

Really? It was a poll for what exactly? How it’s used, if it’s used, what’s it’s used on? Better yet what type (single diaphragm vs dual)? Your initial post said nothing at all about what you wanted.

No disrespect meant but it’s a waste of time as there is no correct answer for all applications...and I still don’t know what it is you are looking for really. I sure hope it’s not to stir up the pot...Randy


Sent from my iPhone using H.A.M.B.

 

read the link that themoose posted above - many variables to consider for correct set up for your motor

 

I understand your thinking, but the I've been around the block once or twice. I very much know the difference between ported vacuum and manifold vacuum. I did drill the carb base after looking things over, and was able to access ported vacuum. Of course the drilling doesn't go below the throttle plates, that would have put me right back where I was before.

 

What distributor and carb are you dealing with? Very important to know to answer your poll question.
Guess this is just a poll.....your not looking for an answer? Takes me a bit to catch on to some of this stuff.

 

throw it away and I run mechanical.

 

Norris, intent of poll is
to answer
“What do you do
with your vacuum hose ?”
(if anything at all)

Not intended to be a trick ?

 

You can always tap into the brake booster vacuum line if you have power brakes and vacuum advance....

 

Holleys I’m familiar with have full or manifold at bottom (angled) and ported at top p***enger side.

Your observation is correct as there is no vacuum at idle off ported (top).

 

Oh, ok....thought maybe I could help.
I’ll play. I don’t have one.

 

...or your vacuum wiper motor

 

A poll is a survey. You will not get an answer, only the most common response. Still doesn't make it correct.
I can't wait for your next how long is a piece of string question.

 

Hey CoG, I am confused! I will be playing with a 3X2s sometime in my future, I hope! Doesn’t the center Ford 3X2s carb have a “ ported” vacuum source, already in the metering block? Is there something I need to know?












Bones

 

Hahaaa, X38,you pretty much read my thoughts, thanks!

 

Bones, I seriously doubt it has one. In those pre-smog-control-days, spewing unburned hydrocarbons out the exhaust was still done with impunity. And Ford didn't care about fuel economy on their Hi-Po motors either, I don't recall Ford installing vacuum advance on any of them prior to '68. Not by coincidence, '68 was also the year the K-code 289 and solid-lifter 427s disappeared. And Ford also didn't really sell any particularly street-friendly Hi-Pos until then either; you could buy a nice, tractable-performing, mid-performance offering or the wild-and-wooly Hi-Pos that were barely-detuned race motors (that also lacked the same warrantee as the vanilla motors). Race motors didn't need vacuum advance, and Ford didn't fit them as OEM, particularly on the FE.