I have an Edelbrock 650 carb on a small block Aat idle there there is no vacumn at the 2 ports at the base of the carb. Checked for leaks . None. Any one experience any thing like this.? Thanks trucke
Those read above the throttle blades. "Ported vacuum". https://www.jalopyjournal.com/forum/threads/ported-vs-manifold-vacuum.1103404/ Or, something is wrong. (I never assume parts are manufactured correctly.)
One is ported the other isn’t. Take wd40 and spray around the base. See if the rpm’s pick up. You might have a vacuum leak. Any flammable non-explosive aerosol can be used to check for vacuum leaks.
Instructions. https://edelbrock.com/pub/media/wysiwyg/documents/carb-owners-manual.pdf page 21, 50 and 51
Wd40, carb cleaner, brake cleaner. Many liquid aerosols will cause the engine to accelerate when sucked in by the vacuum leak
Starting fluid (either) is explosive. Gasoline vapor is explosive. Wood is flammable but not a liquid. If someone is lacking the common sense to not be able to understand the difference between an explosive liquid and a flammable liquid (flammable in the environment they are using it) the shouldn’t be working on a car engine with moving parts. Just like if someone has nothing better to do than try to pick the fly specks out of your fecal matter, they probably shouldn’t be on a site intended to help people fix problems.
Actually in the environment we are talking about, they are both explosive. Here is a web search definition that might help explain the difference. “Flammable refers to, specifically, a substance that easily ignites at or below room temperature, i.e. 73° F (~23° C). Explosive detonates, as in it burns at a rate in excess of the speed of sound. ” Any open flame can explode gasoline vapor and certainly either vapor. Specific conditions have to be met to make combustibles explosive. If someone can’t grasp the concept, they should leave checking for vacuum leaks to someone else.
In that case water vapor is also explosive. The environment we're talking about it hosing down the base of the carburetor with a chemical to check for a vacuum leak. We're not talking about lighting a brushfire with 5 gallons of gasoline, or a combustion & spark induced Diethyl Ether explosion. Anyway, to the OP... the quickest way of checking for vacuum leaks by spraying something around the carburetor, intake, brake booster, etc. doesn't always detect the issue. Like others have mentioned....the wrong base gasket could block a port, or any variation of issues could be the culprit. The original question/issue is too vague to get specific with. Put a vacuum gauge on it and read what it's doing and go from there. A lot of people dismiss the use of a vacuum gauge as being some useless step that they don't understand, but the vacuum gauge will clearly tell you the condition and tune of your engine within seconds.
I worked at a dealership once that had vacuum leak finding apparatus that was essentially a can of propane and a hose (It was GM or Snap On). If you are worried about blowing up, squirt water around. Instead of speeding up, it will slow down when you cover the leak. Mike
If you've ever used, or seen used, ether to seat a tire on a wheel, you would change your definition of it to EXPLOSIVE!
Yes safety is # 1 .common sense to all! Update: I have vacumn at carb port for brake booster and on intake manifold port. Using edelbrock intake . No vacumn at base of carb. Trucke thanks
@old trucke the pdf link I posted has the full instruction sheet for the carbs, including exploded views and the exterior features picture.
They you probably have a blocked port. If you really had no vacuum at idle, you would not have an idle. Carburetors are garage ornaments without vacuum.
motor runs fine under acceleration. when stopped in automatic drive runs real erratic. vacuum leak cause this? Stock 65 T-Bird 390. using non lit propane good way to find leaks?
Yes. You aren't the OP, so perhaps you'll offer up more detail of what its doing at idle and what carburetor?
Had that happen recently on my daily driver barge. Mice were building a nest on top of the motor, and ate one of the vacuum lines. At idle in gear, felt like it was running on 3 cylinders.
guess will do listening test. if no luck will try propane. do not want to spray a carb cleaner, etc over motor.
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