Stop in for a cup of coffee

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Sublime one said:
Well it has been a whirlwind last thirty hours or so. Our boy appeared on our doorstep yesterday with his two kids (14,10year olds)after rescuing them from his X down in Texas. He is on his way home to Clevland. Not sure how it is going to shake out but lots of changes and some court appearances are eminent. And all of this the day before Jodi has surgery this morning on her knee. Well good morning all y’all!
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Hope the best for your son and Jodi.
 
Dumb question but here it goes. Vacuum advance mostly helps idle and transition run characteristics when connected to manifold vacuum, yes? I know there are some rabbit hole threads on this, but just need an answer. Not comparing manifold vs ported, just asking what I am losing running without any for the short term. Rich idle?
 
Fuel milage is the main thing lost.
Doesn't change the mixture.
Changes the efficiency of how much of the burn is pushing down on the crank.
 
Mattax said:
Fuel milage is the main thing lost.
Doesn't change the mixture.
Changes the effeciency of how much of the burn is pushing down on the crank.
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Thanks Matt. I was on the right track then. Time to pull the intake top and drill/tap for a fitting so I can reconnect. It will be another test to see how adding the advance back in works with the Idle-Eez style bleeds
 
Mattax said:
Fuel milage is the main thing lost.
Doesn't change the mixture.
Changes the efficiency of how much of the burn is pushing down on the crank.
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Might change low rpm throttle response a bit.
Without vacuum advance can ran a real quick mechanical advance from idle to 2500 or so.
Enough differnce to be noticible? maybe.
 
Hope it goes well and the nurse give you a happy ending!

im-funny-laughing.gif
 
71GSSDemon said:
Thanks Matt. I was on the right track then. Time to pull the intake top and drill/tap for a fitting so I can reconnect. It will be another test to see how adding the advance back in works with the Idle-Eez style bleeds
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No place convenient in the baseplate to tap for another fitting?
 
Mattax said:
Might change low rpm throttle response a bit.
Without vacuum advance can ran a real quick mechanical advance from idle to 2500 or so.
Enough differnce to be noticible? maybe.
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I do have a pretty quick mechanical advance all in by 2500 IIRC
 
71GSSDemon said:
Dumb question but here it goes. Vacuum advance mostly helps idle and transition run characteristics when connected to manifold vacuum, yes? I know there are some rabbit hole threads on this, but just need an answer. Not comparing manifold vs ported, just asking what I am losing running without any for the short term. Rich idle?
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Manifold vacuum will advance the vacuum timing full in at idle and as you accellerate it backs off then builds agin when the vac steadies. Good for racing not so good for the street. Call me I can walk you through it easier on the phone. Those threads all go sideways. personally I run a full mechanical distributor in the Pop. Pros and cons of ported, manifold and just mechanical.
 
Mattax said:
No place convenient in the baseplate to tap for another fitting?
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No, not really. Going to check to see if I have height clearance for a carb spacer. Then I could easily add in the PCV valve
 
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halifaxhops said:
Manifold vacuum will advance the vacuum timing full in at idle and as you accellerate it backs off then builds agin when the vac steadies. Good for racing not so good for the street. Call me I can walk you through it easier on the phone. Those threads all go sideways. personally I run a full mechanical distributor in the Pop. Pros and cons of ported, manifold and just mechanical.
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I think the idle vacuum on that engine is pretty low. It may not make much differnece.
 
Coffee time. The wife's lunch is made and her coffee too. Time for mine.
 
halifaxhops said:
Manifold vacuum will advance the vacuum timing full in at idle and as you accellerate it backs off then builds agin when the vac steadies. Good for racing not so good for the street. Call me I can walk you through it easier on the phone. Those threads all go sideways. personally I run a full mechanical distributor in the Pop. Pros and cons of ported, manifold and just mechanical.
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Thanks Ray, I will call you in a short bit
 
Morning guys quick fly by before heading to work.
Well not really flying by more of a drag my *** out the door.
 
Mattax said:
Those usually don't like vacuum advance on top of them.
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Engine willbe fine with vacuum advance when using a mechanical advance shaped like this.
1683722474475.png


or these
1683722420987.png



And with no vacuum advance it will be OK with a fast curve like this.
1683722610621.png


Can't mix the two.
Below 3000 rpm or so will result in too much lead time at light and part throttle.
It will manifest as flat spots on the throttle response and /or pinging under moderate throttle once the engine is fully heat soaked.
 
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