Thread: How to connect Vacuum

Tweet

I have rebuilt my sons 350 with high performance options. The only thing missing is how to best connect the distributor vacuum advance and the transmission vacuum modulator.

Should I get a PVS, if so which one? Or, should I use full time vacuum and how is taht done?

you would have to look at the carb paperwork to find the right port for the dist. and the pcv valve. the tranny can be hooked up anywhere that offers full manifold vacuum.

Roger on the trans vacuum modulator being hooked to full time vacuum.

Let's back up a bit on the distributor. More info would help.

- What high performance equipment did you use?
- How radical is the camshaft?
- What carburetor is on the engine?
- Do you have a stock or a high performance distributor? HEI, I assume. If not, what is it?

All of this is important because a distributor often has to be recalibrated for a performance engine. The stock vacuum can may put in too much vacuum (or too little), and at exactly the wrong time.

I've allways used the after market wieghts to go in the distributor, and did away with the vacuum on the distributor.


~ Vegas ~

i concur. thats the correct answer.


henry rifle Quote......
Roger on the trans vacuum modulator being hooked to full time vacuum.

Let's back up a bit on the distributor. More info would help.

- What high performance equipment did you use?
- How radical is the camshaft?
- What carburetor is on the engine?
- Do you have a stock or a high performance distributor? HEI, I assume. If not, what is it?

All of this is important because a distributor often has to be recalibrated for a performance engine. The stock vacuum can may put in too much vacuum (or too little), and at exactly the wrong time.

Thank you for all the response. Here is my situation. 350 bored .040 with 305 heads. 11:1 compression, full race cam, balanced crank. Edelbrock intake with Holley 600CFM Electric choke, vacuum 2ndaries. stock distributor.

I have one hole left open on top of the manifold. What do I do there?

BTW, it is a stock HEI distributor...

Originally posted by peterinak
BTW, it is a stock HEI distributor...

the only thing in ? is the dist., the trans. need to be manifold vac. and the vac. line that goes inside the car to work the heater and ac needs to be manifold. if you have any open you dont need cap it off. plug it up.

the pcv valve should be hooked to the base if the carb. if you are using one.

use the ported vac. to your dist. first and drive it for a while and then hook it to manifold vac. and see the dif., dif. cars and people like dif. things. it wont hurt anything.

even if the dist. needs to be recalibrated that has nothing to do with the vacuum source. You dont want to hook the dist. up to full vac because it would allways be at full advance, limiting your bottom end. I've built alot of engines, high performance, street, and marine high performance and have allways hooked the dist. up to the correct carb port. Engine vacuum is not adjustable under the carb, by hooking up to the port that recieves the vacuum that is created in the veturis the dist. will advance with the throttle.

with more cam you will lose low speed vacuum. it will hurt driving economy and increase emissions if your state has roads side smog sniffer they might sent you a letter, usually for off the line throttle response you will need more low speed advance. just cranking the distributor to 16 or 18 degrees will give you to much at top speed you need to get the distributor recurved and limited total advance. old trick from the 50's i was an engineer at ford, drove a buick powered willys to work every day. had a corvair powered dunebuggy but eventually did buy some new ford products when the finally started giving employee discounts( cheaper than the dealers factory cost)

Originally posted by DennyW

i couldnt find the right words either.

Uh oh . . .