I just got a 69 f-250 with a stock 360 2v,4 speed,no power steering,no power brakes. I was timing it,and when I was done I put the vacuum advance back on,and noticed there was no difference? The hose is connected to the carb,which seems to have next to no vacuum at all? Is this where the hose should be connected? I looked for a place on the intake to try it,however there were no places available?? If anyone knows about this subject, any advice would really be appriciated. Thanks!

 

yeah theres two different vaccums ported and timed i think. One has no vaccum till ablout 800rpm or more and the other has vaccum at idle.

 

Ported and Timed are the same thing. You meant ported(or timed) and Manifold. The rest of your description was fine.

 

yeah the problem was i never reaaly got it straight from the beginning. The manifold has vaccum at idle and ported is after about 800rpm.

 

pull the vac line off the carb and suck on it. watch the inside of you distributor to see if the advance arm moves.

 

After the throttle is lifted off idle, the two ports should read the same. I have found that mine idles better if I plug the vacuum advance directly into the manifold vacuum.

The reason they ported the vacuum through the carb was so that it wouldn't advance at idle, helping with emissions.

 

i use ported because i have a lot of vaccum in my engine. i have to set the base timing atdc to run manifold. I did notice that manifold seemed to help low and midrange response and power though.

 

"After the throttle is lifted off idle, the two ports should read the same. I have found that mine idles better if I plug the vacuum advance directly into the manifold vacuum.

The reason they ported the vacuum through the carb was so that it wouldn't advance at idle, helping with emissions."

You continually post this misinformation.

Vacuum advance has been ported from the carb since the dawn of time, way before emissions. Why?

Because a revved engine needs a splash of gas (accelerator pump) and a dash of advanced timing (vacuum advance.)

Once again: vacuum advance connects to the carb, NOT the manifold. It has NOTHING to do with IDLE!!!!!!!!!!!!!!!!!!

If your engine idles better with the vacuum advance plugged into manifold vacuum, then there is something basically wrong with it. Every engine I have ever worked on that was basically OK idled better with vacuum advance connected to the carb, as it should be.

 

Okay, so is the check for the vacuum advance valid? I am at that stage in a tune up for my 360 and was told that old vacuum advances sometimes don't even work. So you pull the cap off the distributor and suck on the vacuum hose?

 

Scroob is correct as to where the vacuum is supposed to connect to as per the books. There are, however, many people who like to set theirs up on manifold vacuum.

I used the timed vacuum port when I ran vacuum advance because I liked setting the idle with no timing advance in. Then when you hit the gas a little your timing jumps way up and all is good. When you connect it to the manifold the timing only has one way to go and that is down until mechanical advance takes over.

Another thing to think about is overheating. If you plug into your manifold directly you will have about 40 degrees of advance at idle. Unless your cooling system is up to snuff you will likely find overheating is common.

I find that engines are more responsive when hooked up to the timed port.

I wanna say it was DF though who likes to use the manifold vacuum but he tunes his entire engine for it.

 

For stock, the ported vacuum is what you should use, but like you said Ratsmoker "some" people use manifold vacuum.

That includes me, but here's why:

With my cam, and 16 degrees initial advance (at idle) I only pull 11 inches of vacuum, and get a somewhat lopey idle, even at 900RPM. But with so much initial advance, it starts hard and it's hard to keep the RPM's down low enough to not burn the clutch getting started.

So, I put an adustable vacuum advance on the dizzy, set it up pretty high on stiffness, and connect it to manifold vacuum. At idle, the timing is 16-20 degrees with the vacuum advance hooked up. Without, static, it's near 5BTDC.

Then, I took two weak springs for the dizzy advance, set the cam to be only 13 degrees (26 crank) max. Ever notice how the strong spring is loose in the dizzy? Beginning mechanical advance stock is only one weak spring initially, then into the hard spring. What I have after two weak springs is a very small initial mechanical advance, manifold vacuum advance, and it all works out. Great low-end for starting out, and plenty of advance where and when I need it.

HOWEVER - this is not a stock motor - if it was, I would go with ported vacuum ...

 

Well, I can only post what I observe. My stock motor likes the manifold vacuum better than the ported. You should hear it idle, it's like EFI after it warms up. It doesn't overheat either. For some reason, it just likes a lot of advance I guess. It doesn't run bad when I plug it into the ported, but it does turn a little slower, and I have to adjust the idle speed to compensate.

Also, you do not want vacuum advance at WOT as scroob says. Neither ported or manifold will pull any vacuum there, so there is no difference.