vacuum test

joe0508 wrote:
What are my options as far a unported vacuum sources?

You want a port that goes direct to the intake manifold. Forget the junk coming off the tbi. Check if you have something like toward the rear in this picture. Worst case remove that casting plug in the front and get a fitting to work. Or you could post a couple pics of your actual set up.

joe0508 wrote:

leeper wrote:
Curious as to what you are trying to do and why?

I am trying to get my vacuum gauge to read correct or how i think it should read.In all the videos that i have seen the vacuum gauge falls to 0 quickly when at full throttle.Mine doesnt quite make there no matter how quick or hard i punch it.Just trying to figure out to why since i am tyed into manafold vacuum.

Thinks that does help.Mine usually stays at 22 at idle.That is close to being high i think.

joe0508 wrote:
What are my options as far a unported vacuum sources?

There is a port on the LH side of the TBI right above the manifold. That's where I installed mine. When at WOT it will get pretty close to 0 about 1. At idle it should read about 21. When descending a hill it gear it will go higher. I made a pointer out of a piece of black tape on mine at 10 so I can see it at a glance because at 10 or above I get the best fuel economy in 4th gear. Make sure your dog house cover is not compressing the rubber hose that will reduce your readings. I made a steel bushing that the rubber hose goes through to prevent that. I am old so I think the vacuum gauge is a good tool for an older eng, carb or TBI. You can tell at a glance as to how your eng is running (sticking or burnt valves, bad rings etc). Also allows you to stay in 4th gear when climbing a hill by adjusting the throttle at a given reading. Hopes this helps you Joe.

leeper wrote:
Curious as to what you are trying to do and why?

I am trying to get my vacuum gauge to read correct or how i think it should read.In all the videos that i have seen the vacuum gauge falls to 0 quickly when at full throttle.Mine doesnt quite make there no matter how quick or hard i punch it.Just trying to figure out to why since i am tyed into manafold vacuum.

Curious as to what you are trying to do and why?

I haven't done gasser tuneups for over 40 years and they were all carbs then. I doubt if you'll ever see 0 but 10" doesn't sound low enough either. The Autolite and Holley carb kits came with an 8.0 power valve and I would put in a 6.5 to help with mpg. The 8.0 meant the power circuit started opening at 8.0" hg. I would think the lowest would be more like 4-5" or there about. Craig

MEXICOWANDERER wrote:
Power brake vacuum connection hose or fitting has true engine intake vacuum.

How can you tell if it is a true engine intake vacuum?Correct me if i am wrong but i believe it is when there is vacuume at idle.If so i must be hooked into true intake vacuum becouse before i hooked it up it was sucking.I think if it not true there will not be vacuum untill you hit the gas.Is this right?

Not supposed to go to Zero. If it does, something's wrong.

Power brake vacuum connection hose or fitting has true engine intake vacuum.

It really shouldn't go all the way to zero and rarely does on a stock engine in that sort of application.
I would worry if it did.