Distributor vacuum ports
Thread Starter
Burning Brakes
Joined: Aug 2002
Posts: 1,146
Likes: 10
From: Scottsboro Alabama
Distributor vacuum ports
I have an Edelbrock Performer carburetor on my ZZ4. There are two ports for vacuum advance.
#1- Timed Vacuum Port, (for emission-controlled engines).
#2-Manifold Vacuum Port, ( for non-emission-controlled engines).
Right now I am hooked up to the timed vacuum port. There are no emission controls on my engine. Am I in the wrong port? How exactly do these ports differ? Thanks for any info......
#1- Timed Vacuum Port, (for emission-controlled engines).
#2-Manifold Vacuum Port, ( for non-emission-controlled engines).
Right now I am hooked up to the timed vacuum port. There are no emission controls on my engine. Am I in the wrong port? How exactly do these ports differ? Thanks for any info......
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Re: Distributor vacuum ports (Older Than Dirt)
The timed port allows vacuum only when the throttle is opened while the other port allows vacuum full time. You are correct in having your timing connected to the timed port.
Racer
Joined: Nov 2001
Posts: 478
Likes: 3
From: Huntsville AL
Re: Distributor vacuum ports (vettfixr)
vettfixer,
I'm at a loss here...hope you can help me out also. On my 81 S/B I'm running the edelbrock 1406 carb. with the 2101 intake and just installed the 2103 cam and lifter set. The instructions that came with the cam said to run un-timed port. Does it depend on the type of cam you are running or what exactly is the determining factor for this? I may have mine hooked up wrong. Thanks in advance.
:confused:
YBNormal...drive a vette
www.angelfire.com/al/swhite7/doug.html
I'm at a loss here...hope you can help me out also. On my 81 S/B I'm running the edelbrock 1406 carb. with the 2101 intake and just installed the 2103 cam and lifter set. The instructions that came with the cam said to run un-timed port. Does it depend on the type of cam you are running or what exactly is the determining factor for this? I may have mine hooked up wrong. Thanks in advance.
:confused:
YBNormal...drive a vette
www.angelfire.com/al/swhite7/doug.html
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Re: Distributor vacuum ports (Ybnormal)
I'm not sure why they recommend running an untimed port. Here's what happens when you set your timing. To set timing you disconnect and plug the vacuum line to the distributor and set it to idle specs. Let's assume that this is 10 degrees BTDC. Once you reconnect the vacuum line to the untimed port your idle is now set at about 25 degree because the vacuum advance kicks in about 15 degrees advance. If you use a timed port the timing at idle doesn't change until you step on the gas and uncover the vacuum port in the carb. Every car I've ever had or read about recommends a timed port. Maybe Lars could help us out with this one.
Le Mans Master
Joined: Apr 2000
Posts: 5,202
Likes: 10
From: cincinnati ohio
St. Jude Donor '09
Re: Distributor vacuum ports (vettfixr)
Edelbrock recommends manifold vacuum advance for a lot if not all their cams.
I would guess their testing shows they work best with a lot of timing at idle??
On a modified motor I don't think you can say one is better than the other...you have to try them both and see which works best for your combo :cheers:
I would guess their testing shows they work best with a lot of timing at idle??
On a modified motor I don't think you can say one is better than the other...you have to try them both and see which works best for your combo :cheers:
Racer
Joined: Nov 2001
Posts: 478
Likes: 3
From: Huntsville AL
Re: Distributor vacuum ports (yellow 72)
Thanks for the reply guys. I just haven't thought about trying it both ways. As soon as I get it on the road again I will give it a shot and see if it makes a difference. Thanks again :cheers:
YBNormal...drive a vette
www.angelfire.com/al/swhite7/doug.html
YBNormal...drive a vette
www.angelfire.com/al/swhite7/doug.html
Burning Brakes
Joined: May 2000
Posts: 774
Likes: 4
From: RI
Re: Distributor vacuum ports (Ybnormal)
Ported vacuum was designed for emission control. It should run better on straight vacuum but you need to have the correct vacuum canister to match your engine set up. You can order a stock HP one or an adjustable one like this Crane canister shown in link
http://www.cranecams.com/master/vacuum.htm
http://www.cranecams.com/master/vacuum.htm
