Edelbrock Carb Question- Vacuum port

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65Valiant310

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Hi all,
I have a 1406 edelbrock 4 barrel carb, and there are 2 small ports on the front. Ive had the left one in use for years, but my 1978 engine with pcv and breather only- no emissions items installed, makes me believe I should switch the port and plug the opposite side. The non plugged one runs to my distributor vacuum.

The left one is labeled as (from edelbrock manual):
3/16” TIMED VACUUM
(Distributor vacuum advance port
for emissions controlled engines)

The right one is labeled as:

3/16” MANIFOLD VACUUM
(Distributor vacuum advance port for
non-emissions controlled engines)

Anyone have an idea which I should be using?
 
Bump an old thread. I feel like nobody understands how the vac advance works. Me included. Everyone I ask says something different. Local shop said, DONT plug in a vac advance, local mopar guy said use the right side port (manifold vac) edelbrock tech says use the left (timed port). Blah.
 
Here's the eddy diagram

temp3.jpg
 
Take a look at the OE carb vacuum port and where it sits in the carb as well as the path the port takes.

Copy OEM.
 
Edelbrock......and my vacuum gauge both say the opposite of what your so called gurus say. The driver's side port is manifold vacuum and the passenger's side is ported, just as in the diagram above. I have an Edelbrock on my F250 and it has the ported vacuum port exactly as in the diagram above.

That said, the guru that told you not to use the vacuum advance is an idiot, just to clear that up now.

The purpose of the vacuum advance is to pull the timing up on part throttle, when the vacuum is high. This helps clean up unburned fuel that would otherwise be wasted out the exhaust on part throttle.

It also aids part throttle response. The last benefit, which is a biggie, is that it increases fuel mileage and by a good bit. Usually 2-5 MPG if tuned correctly. So anyone who says not to run vacuum advance on the street doesn't know a farfegnoogen thing about how it works or what it does.

Just because guys disconnected it forty years ago and thought it was cool doesn't mean it's a good thing to do.

The vacuum advance will even work with large camshafts, as at part throttle, vacuum is greatest in any engine. The bottom line is, if you drive your car on the street AT ALL, you will benefit from vacuum advance, PERIOD. End of story.
 
RustyRatRod said:
Edelbrock......and my vacuum gauge both say the opposite of what your so called gurus say. The driver's side port is manifold vacuum and the passenger's side is ported, just as in the diagram above. I have an Edelbrock on my F250 and it has the ported vacuum port exactly as in the diagram above.

That said, the guru that told you not to use the vacuum advance is an idiot, just to clear that up now.

The purpose of the vacuum advance is to pull the timing up on part throttle, when the vacuum is high. This helps clean up unburned fuel that would otherwise be wasted out the exhaust on part throttle.

It also aids part throttle response. The last benefit, which is a biggie, is that it increases fuel mileage and by a good bit. Usually 2-5 MPG if tuned correctly. So anyone who says not to run vacuum advance on the street doesn't know a farfegnoogen thing about how it works or what it does.

Just because guys disconnected it forty years ago and thought it was cool doesn't mean it's a good thing to do.

The vacuum advance will even work with large camshafts, as at part throttle, vacuum is greatest in any engine. The bottom line is, if you drive your car on the street AT ALL, you will benefit from vacuum advance, PERIOD. End of story.
Click to expand...


Got it! I'm gonna run it. I was running it off the driver side. When it said "emissions" vehicle for the other side, I just assumed that wasn't correct. lastly, if I use the timed port, I assume I use the other to check manifold vac at idle to help set timing?

Thanks for the info!
 
Neither port is "wrong." GM used manifold vacuum for a lot of their cars back in the '60s, and in some cars, it smooths out the idle and helps to keep the engine cool in traffic. It makes other cars nervous (the idle hunts). Out of my six old cars, three are running ported vacuum and three are running manifold vacuum. Neither has caused any catastrophes.
 
Left side right side drives me nuts lol.
Easier with passenger side and driver side.
I have always had my 273 hooked to timed port on pass side. It needs fine tuning but has to wait till its out of hibernation in spring
 
Passenger side = right side
Driverside = Left side
 
Aaron65 said:
Neither port is "wrong." GM used manifold vacuum for a lot of their cars back in the '60s, and in some cars, it smooths out the idle and helps to keep the engine cool in traffic. It makes other cars nervous (the idle hunts). Out of my six old cars, three are running ported vacuum and three are running manifold vacuum. Neither has caused any catastrophes.
Click to expand...

That's correct. The important thing is to adjust initial timing accordingly regarding which port you use. So that means it will take a good bit less initial timing if you use the ported vacuum port.

I have used manifold vacuum on the distributor can in the past and I simply left it hooked up and adjusted initial. Worked for me.

That said, even still, I always had the best results using ported vacuum.
 
I checked and just realized that I ran mine off the passenger side port, and a vacuum gauge on the driver side port.
 
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