Vacuum Advance mystery

On my small block Chevy with 3 deuce Edelbrock intake, it started running terrible so I pulled the vacuum hose off to check the timing and found that the timing is the same with or without the vacuum hose.

I thought that maybe the vacuum advance had gone bad and got my Mity-Vac and then dropped it on the concrete so now the gage doesnt work.

So I got a new made-in-the -USA vacuum advance and put it on and got the same results.

I checked and the new vacuum hose is not blocked.
Then I took the vacuum hose fitting out of the manifold and with this open hole in the intake, the engine speeded up!

I am baffled.

What causes the engine to speed up with an open hole in the intake manifold?

 

Running rich... Better check your carbs out.

As far as the advance goes, do you have the advance hooked to ported vacuum? If so, removing the hose will have no effect at idle. Vacuum is only present on that port as the throttle plates come open. It should be hooked to the manifold vacuum port.

 

No, It should not be hooked to the vacuum port. It should be hooked up to the Timed port coming off the carb.

 

Yeah, if you like emissions era technology and overheating in traffic.

Manyolcars, Are you running HEI or point dist?


Here's some good reading on the subject. I think Tommy originally posted this on here:
http://www.hotrodders.com/forum/distributor-tuning-theory-part-1-a-59033.html

 

Yea, you are right, If he is running a HEI, he needs to run ported. If he is running points he can run manifold. As for the ported is only for emissions, I used to subscribe to that theory too. Until I had a car that I could not for the life of me get to run right. Poor acceleration, ****py gas milage and would exhibit a condition that resembled valve float at high RPMs My neighbor (who has been around cars and hot rods his whole life) saunters over, beer in hand, looks at the engine, pulled vacuum hose for the distributor from the manifold to the ported and presto, new car And I was running a points distributor.

 

My sbc w/Qjet runs like krapp with any vacuum line on the dist

 

Sbc is in my wife's roadster the dodge is dodge power

 

"...Then I took the vacuum hose fitting out of the manifold ..."

Thank you for the link Thunderbird,
It is a points distributor