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+--- Thread: Timed vs full??? (/thread-2698.html)
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Timed vs full??? - Crawdad - 03-02-2011
Carb questions for the experts. I figured since I laid down 3 big ones for this carb, I figured I would atleast read the directions before starting my journey. The first thing the directions ask for is "Determine if the distributor vacuum port is timed (no vacuum at idle) or full (vacuum present at idle)", see pic #1. In #2 pic you will see where the line hooks onto, either 3/16" timed vacuum OR the 3/16" manifold vacuum.
I feel since my 76 bronco is so old that it is considered a "non-emmisions controlled engine", is that safe to assume???
Timed vs full??? - blazinchuck - 03-02-2011
you would want ported vac for that and full vac for brake booster(if present) so im thinking the timed vac in this case
Timed vs full??? - jdowns67 - 03-02-2011
Check the web and there's differing theories on which to use. I tried both and had the best results with neither. Vacuum advance is only there for economy purposes when you are running at part throttle and completely goes away when you have your foot in it. Vacuum advance doesn't do anything to improve performance at mid throttle to wide open throttle.
Timed vs full??? - bucketobolts - 03-02-2011
The vacuum advance should be connected to the manifold source. You should also double check the advance solenoid and that the advance plate is functioning properly in the distributor. Set your base time and idle mixture with the line disconnected and capped. Then install when your done.
This will allow you idle the carb a little lower and leaner. The vacuum advance will help smooth the idle, then it will drop out as vacuum decreases and the centrifugal advance will take over when accelerating. After reaching cruising speed, the vacuum advance will add to the mechanical increasing fuel economy and drivability.
Timed vs full??? - Crawdad - 03-02-2011
bucketobolts Wrote:The vacuum advance should be connected to the manifold source. You should also double check the advance solenoid and that the advance plate is functioning properly in the distributor. Set your base time and idle mixture with the line disconnected and capped. Then install when your done.
This will allow you idle the carb a little lower and leaner. The vacuum advance will help smooth the idle, then it will drop out as vacuum decreases and the centrifugal advance will take over when accelerating. After reaching cruising speed, the vacuum advance will add to the mechanical increasing fuel economy and drivability.
If you dont mind, let me pick ur brain a few times.
1) What is a manifold source? Do I need to drill a hole in manifold? Picture?
2) What is an advance selenoid? Picture?
As my dad would always say to me "Son!! Do I have to draw you a damn picture!!!!" Thx a bunch for your input!
Timed vs full??? - Crawdad - 03-02-2011
bucketobolts Wrote:The vacuum advance should be connected to the manifold source. You should also double check the advance solenoid and that the advance plate is functioning properly in the distributor. Set your base time and idle mixture with the line disconnected and capped. Then install when your done.
This will allow you idle the carb a little lower and leaner. The vacuum advance will help smooth the idle, then it will drop out as vacuum decreases and the centrifugal advance will take over when accelerating. After reaching cruising speed, the vacuum advance will add to the mechanical increasing fuel economy and drivability.
I'm passing time at work and thought I would do some research on the web. Is this what you are talking about: http://www.chevelles.com/forums/archive/index.php/t-94121.html
Timed vs full??? - bucketobolts - 03-02-2011
Crawdad Wrote:1) What is a manifold source? Do I need to drill a hole in manifold? Picture?
Manifold vacuum should be the port in the front of the base plate. It will have a pretty good vacuum on it at idle.
2) What is an advance selenoid? Picture?
The solenoid is the diaphragm on the front of the distributor.
I'll have to see if I can get a couple of pictures.
Timed vs full??? - Crawdad - 03-02-2011
bucketobolts Wrote:I'll have to see if I can get a couple of pictures.
I took a few more pics.
Timed vs full??? - jdowns67 - 03-02-2011
Didn't you say you were installing a Edelbrock performer carb right? If you choose to use full manifold vacuum, connect the vacuum line from the distributor to the 3/16" port to the right of the PCV connection, if you choose to use the timed connection, use the one on the left. The difference is that the full manifold vacuum port comes right off the intake manifold so it has vacuum all the time. The timed port is just above the throttle valve so there's no vacuum at idle, but as soon as you crack the throttle, there's vacuum there. Do you remember when I told you to get a vacuum gauge? If you choose to use the manifold vacuum source, you need to put a T in the line to connect your vacuum gauge to adjust your mixture. This is because connecting the distributor to full manifold affects the idle speed and mixture. Using full manifold vacuum will also make the starter work just a little harder getting the engine going. I also agree with Bucket of Bolts second paragraph.
I have tried to use the timed connection before. What I ran into is that at the moment I cracked the throttle when I was taking off, the shock to the distributor of going from zero vacuum advance to full vacuum advance caused a bad hesitation. If I were going to try to use vacuum advance again, I'd probably try full manifold.
I think a lot of it depends on your distributor and how much vacuum advance it pulls in. I guess I'm not using vacuum advance right now because I don't care that much about economy because I don't drive my Bronco every day. It just runs too good for me to mess with it. I'm sure there are folks that will disagree with what I've said but it's just my opinion..and everybody's got one right?
JD
Timed vs full??? - bucketobolts - 03-02-2011
From those pics, it looks to be connected correctly.