?? on Carb vacuum port

[BarryK]

On my L76 motor I have a correct replacement 2818-1 carb.
Everything I've read on here indicates that my vacuum can on the distributor should be hooked up to the FULL vacuum port, not a PORTED vacuum port on the carb which i thought mine was.
I was at a tuning session yesterday and had Lars (from the "other" site) tune my car and she is running better than she ever has before but after checking everything he determined that the port on my carb is only a ported vacuum port, not a full vacuum port and my carb has no full vacuum port available which was surprising.
Isn't the 2818-1 suppose to be a full vacuum port? If not, how much am I losing in performance by only having a ported vacuum controlling my vacuum advance? I do have a plugged hole on my intake right behind the carb - would I be better off getting a fitting for that intake hole and running the vacuum advance directly off the intake manifold rather than the carb?

Any and all suggestions or advice is great appreciated as always!

 

[motorman]

On my L76 motor I have a correct replacement 2818-1 carb.
Everything I've read on here indicates that my vacuum can on the distributor should be hooked up to the FULL vacuum port, not a PORTED vacuum port on the carb which i thought mine was.
I was at a tuning session yesterday and had Lars (from the "other" site) tune my car and she is running better than she ever has before but after checking everything he determined that the port on my carb is only a ported vacuum port, not a full vacuum port and my carb has no full vacuum port available which was surprising.
Isn't the 2818-1 suppose to be a full vacuum port? If not, how much am I losing in performance by only having a ported vacuum controlling my vacuum advance? I do have a plugged hole on my intake right behind the carb - would I be better off getting a fitting for that intake hole and running the vacuum advance directly off the intake manifold rather than the carb?

Any and all suggestions or advice is great appreciated as always!

having full vacuum at idle will help keep the engine temp down. most holleys can be converted from ported vacuum to full vacuum with some work with a die grinder

 

[BarryK]

me with a die grinder on my carb sounds like a very dangerous thing...........

 

[ctjackster]

holley 2818 has a fitting for full manifold vacuum, and you can is plumbed into this. I am unable to explain how it can be pronoiunced ported vacuum, unless your Holley was somehow modified, which I doubt.

I assume your vac line from the can is routed like mine ?

 

[BarryK]

Jack
yes, my vacuum line is routed the same way.
JohnZ replied on the other site regarding this and that while the original 2818-1 carbs were full vacuum ports the later service replacement units like the one I have were changed to ported vacuum and suggested I use the open plug on the intake manifold.
He didn't know why they made the change on the carb though but I'd guess that since it happened a number of years later maybe it was for emission requirements??
Whatever the reason for the change on the carb it looks like changing my vacuum line from the carb to the intake is another winter project.
I'll just have to figure out a way to plug the carb's ported fitting when I move the line to the manifold in such a way so that it doesn't look like crap or too much of a bubba method. Hmmmm, I wonder if that fitting on the carb can be unscrewed off and than just replaced with a solid screw-in plug?

 

[ZRGator]

Didn't you just have the car tuned by Lars? If anything was wrong with your current set up, wouldn't he have noticed and/or said something?

I don't quite understand the problem here, I guess.:confused

 

[motorman]

Jack
yes, my vacuum line is routed the same way.
JohnZ replied on the other site regarding this and that while the original 2818-1 carbs were full vacuum ports the later service replacement units like the one I have were changed to ported vacuum and suggested I use the open plug on the intake manifold.
He didn't know why they made the change on the carb though but I'd guess that since it happened a number of years later maybe it was for emission requirements??
Whatever the reason for the change on the carb it looks like changing my vacuum line from the carb to the intake is another winter project.
I'll just have to figure out a way to plug the carb's ported fitting when I move the line to the manifold in such a way so that it doesn't look like crap or too much of a bubba method. Hmmmm, I wonder if that fitting on the carb can be unscrewed off and than just replaced with a solid screw-in plug?

holley sells rubber cap offs for this pupose

 

[BarryK]

Dennis, yes Lars just tuned my car. He was the one that pointed out to me that the vacuum can line connection on the carb was a ported one. He tuned my car around this since we didn't have the time nor the parts to start changing the vacuum line around.

Motorman, thanks for the info. That saves me some looking around for the line cap I'll need.