Tuning with vacuum. School me please.

So I found this site http://www.secondchancegarage.com/public/186.cfm
It talks about tuning and iterpeting your engines condition by using a vacuum guage. I did have a few questions. Which port do you hook up the guage to? Do I disconnect the vacuum advance on the distributer?
Lastly does this work as well as the article claims it does? In case it matters the engine I have is a Chevy 250 with a Pertronix points eliminator and Pertronix coil. Thanks, Todd

 

connect it to the manifold.

I tried getting useful info out of a vacuum gage a long time ago...gave up on it...and never tried again. I'd suggest reading tea leaves as a more useful method

 

Good article for us non-trained back yard tinkerers. I really like the animated scenarios. Never seen anything like that before. Neat.

When I tune using a vacuum gauge I monitor straight manifold vacuum with a T-Piece off a manifold vacuum port and I just adjust mixture and timing until I get the highest vacuum reading. I then check the initial timing again just to make sure I haven't gone too far. At first I had doubts as to using this "blind" method of tuning but it worked for me. I don't disconnect the vacuum advance unless I'm physically setting the initial timing. Other's I'm sure will know more.

 

SQUIRREL - Where do you hook up the tea leaves?...

 

Duh!!! You put 'em in the radiator and read the overflow.

Sheesh.

Cosmo

 

One says it works. One says it doesn't. Not very encouraging.

 

It works. Engines have vacuum and vacuum is a good indicator of tune. Tune to the highest vacuum signal that you can obtain within normal timing and mixture paramters. Not sure how it can not work.

http://www.google.com.au/search?hl=en&rlz=1W1GGLL_en&num=100&q=vacuum+gauge+tuning&meta=&aq=f&oq=

 

What 32FORD5 said. Hook your gauge up to manifold vacuum, and tune to the highest, steadiest reading you can get. That tutorial you found is a very handy one to have...it tells it all...

 

When gas prices went up last year, I installed a vacuum gauge permanently next to my other gauges on the dash on both my daily rides.
It not only tells the condition of the engine, but also helps getting better gas mileage in town and on the freeway.
Gauges from the 50s-70s had another scale showing fuel economy. Kind of like a simple gas mileage indicator. (like this one below)
I check it more often than the speed and rpm gauges.

 

It does work. When you buy a new gauge there will be instructions with it.They describe how it works. When properly set up on a running engine, the gauge's needle will exhibit certain characteristics which correspond to or identify certain conditions (of wear) that the engine is in.
I've found them useful to identify potential problems that you can't sense like bad valve springs,slight vaccuum leaks,etc.
Oh yeah! and what Squirrel said,,, make homemade tea when your out there diagnosing engine problems as it's very refreshing. You can always switch to beer when you're done solving those problems.

 

I'm confused, just how many of those tea leaves does it take? Any brand better than others? That green tee, use that for reading the newer 'green' cars or does it work on older models too? Just wondering you know.

 

When I used a vac guage to set timing I always brought it up to max vac then backed it off 1 to 2 inchs otherwise the engine would ping.
Just my .02 cents

 

I've adjusted my carbs using a vacuum gage for years. Always worked for me.

 

And here Ive been using Long Island Ice Tea

http://www.classic-cars-online.co.uk/Archive/vacuumgauge.html

good info.

 

Think about what a vac guage tells you when tuning at idle. You adjust mixture for highest idle which means highest vacuume. This means you are adjusting for complete combustion of the highest charge. If you go too rich, combustion suffers and power drops, slowing the idle. If you go too lean, fuel saturation suffers and power drops, slowing idle. The idle slowing is visible on the vac guage. When you use a tach for this, you seek highest idle, turn it down with the screw and repeat ntil you get the lowest possible idle. That works because you optimized the idle speed at each step looking at the tach. You can do the same thing with a vac gauge looking for the needle to drop or peak. It's not rocket science.

 

Yes, adjusting timing to get the most vacuum will result in timing that is too advanced.

I just re did mine with the vac gauge and went up to max and backed it off 2 inches or so, and re checked with a timing light and it was real close.

 

Thanks for posting, some useful information on this site.link http://www.secondchancegarage.com/index.cfm

 

Adjusting timing with a vacuum gauge? Not what I would do. It may be used to adjust idle mixture if you are deaf, but the best use for one is as a diagnostic tool for a sick motor, and as a tool to determine the optimum power valve value. Timing is best adjusted using the instructions that came with the curve kit and adjustable vacuum advance, time consuming but the only way to fly!

 

i was told to get max vacuum then retard the timing 2 degrees