Distributor vacuum port questions

[antome]

Hello,

I have a question regarding the distributor on my 67 200ci. There appears to be 2 vacuum ports and I am wondering why this is and why only one of them is hooked up. I have a Holley 1940 carburetor and the upper port on the distributor is connected to the carburetor, but the other one just has a ~1 inch cut off hose for no apparent reason. I have read somewhere that some distributors had a second port for vacuum retard functionality, but what does that really mean?

So to sum up my questions:

1) What is it for?
2) Is the correct one connected to the carburetor?
3) Is it ok to leave it like this or should i plug the unused port?

Here is an image of it:

Thanks!

 

[rbohm]

that looks like a distributor with the vacuum retard capability. california cars had that set up so that they could retard the ignition timing when the engine warmed up to reduce emissions. there should be a vacuum tree somewhere that is bolted to the cooling system in some manner to achieve this. i think you have the vacuum hose in the wrong place though, as i recall the outer tube is the advance and the inner one is the retard function. its been a while though so check to be sure. the nice thing is that you can use this if you decide to run boost. just run the vacuum line to a point where it will see both vacuum and boost pressure, and whent eh boost comes on it will retard the ignition timing. and it is fine to leave the one port open if you like, or plug it doesnt matter.

 

[CZLN6]

Howdy Back Antome:

Your mystery head has now become a mystery engine. The distributor is either a Calif Emissions type from 1966 or '67, or a "correct '68 or '69" distributor. The Holley #1940 is a Service replacement carburetor, replacing the OEM Autolite 1100. The Original 1100 in the above years did not have a Spark Control Valve (SCV) and had centrifugal as well as vacuum advance. rbohm covered the typical connections between this distributor and a stock 1100 carb, but since the #1940 is a service replacement carb, that could be had in many iterations, it is probably a good idea to take a good look at your carb next to verify that it is a non-SCV carb but has a ported vacuum source.

If the service replacement carb is correct for your engine then switching the vacuum line to the outer nipple is the way to go. Further more, I'd suggest leaving the inside nipple un-sealed/open. Set your initial ignition advance at 10 degrees btdc and check out the way the engine responds.

Next time you have the distributor out check for casting or manufacture codes to verify what distributor you have. Keep us posted.

Adios, David

 

[antome]

Thanks for the info!

My Holly 1940 does not have a SCV and it has the vacuum port hooked up, but whether or not that is the correct setup or if it has been modified at a later time I do not know. There is also no guarantee that the distributor is the original one. I am happy to find out about the vacuum ports for the distributor because I have kind of always wondered what the second port was for but never got the time to look it up. I will change to the outer port and see how it responds. I'll post back as soon as I get some results.

Sorry for changing the topic a bit but the reason why I am bringing this up now is actually because I am thinking about swapping the Holley 1940 1 barrel to a Holley 2300 2 barrel 320 cfm. I got an adaptor plate for it from a friend so I figured I would give it a try. The vacuum setup for the 2300 should be about the same as for the 1940, am I correct?

Apart from that, is there anything else I should know about the swap before attempting it? I of course know about the obvious things such as throttle linkage, hood clearance and possible choke differences. I also know that ideally to get the most power I should consider a "2V conversion" but I do not want to modify the head since I want to be able to go back to stock should I ever decide to do that.

Thanks!

/A

 

[CZLN6]

Howdy Back A:

Let us know how the changes of vacuum lines goes.

On the 2300, be aware that hood clearance/air cleaner clearance may be and issue. The other is that you may have to fine tune with jetting once you get is going good.

Adios, David