How much vacuum?
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How much vacuum?
I just got a brand spanking new Holley 2300 (500 CFM) for my 352cid and man what a differance. I bought a new vacuum gauge so I could set the idle mixture and was wondering what my vacuum should be at an idle and where the best place to hook the gauge too. I hooked it to the port for the vacuum advance and at an idle the needle didn't move off 0, only when I advanced the throttle to about 2000rpm then it moved up to the green. Any advice for this shade tree machanic??? Happy Turkey Day 
Postmaster
Joined: Apr 2002
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From: Coal country
The carb worked exactly as designed - the vacuum advance port is "timed" or "ported" vacuum. That is, it doesn't apply vacuum until the carb is opened up a bit.
You need to find the other port, which has vacuum full time.
A well tuned engine should run about 18 in/Hg.
You need to find the other port, which has vacuum full time.
A well tuned engine should run about 18 in/Hg.
Postmaster
Joined: Nov 2001
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From: Escondido, CA
The port you are hooked up to is for the vacum advance for the distributor. That is normal until it comes off the idle ciruits. You want to hook it up to a different port. I would disconnect the automatic vacum hose from the back side of the intake manifold to get an open port. Or you can find another port on the carb that is registering with the engine at idle.
The cam will dictate how much vacum you have so there is no set specification you need to adhere to. I have always set the idle screws to get the highest reading. To do this start the engine and adjust the idle IN until the engine starts to die. Then slowly screw it out until you get the highest reading. You will have to fiddle with it a little bit remember not to keep screwing the mixture screws out any farther when you get that reading. If you do all you will be doing is wasting gas.
The cam will dictate how much vacum you have so there is no set specification you need to adhere to. I have always set the idle screws to get the highest reading. To do this start the engine and adjust the idle IN until the engine starts to die. Then slowly screw it out until you get the highest reading. You will have to fiddle with it a little bit remember not to keep screwing the mixture screws out any farther when you get that reading. If you do all you will be doing is wasting gas.
Postmaster
Joined: Nov 2001
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From: Escondido, CA
Nice to see two people can type just as fast as the other.
I did forget to ask one question though. Do you have a stock/dual plane intake? If so try to get a vacum reading from both sides of the intake to set both sides of the engine for what they need. Trying to do this with a single plane intake is a bear.
I did forget to ask one question though. Do you have a stock/dual plane intake? If so try to get a vacum reading from both sides of the intake to set both sides of the engine for what they need. Trying to do this with a single plane intake is a bear.
Last edited by airharley; Nov 22, 2006 at 09:01 PM. Reason: missing info
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Got it! The carb was almost right on. got just a hair over 18 HG and no flucuation on the gauge. Not bad for a tired old engine. 
I will run it like that for a while and then check the plugs. I think it is still to rich. I hope I don't have to jet it down. The altitude here is about 2500ft. the factory jets are 73's and the book says it is set at sea level and to come down one size for 2000ft. Any advice on that.
I will run it like that for a while and then check the plugs. I think it is still to rich. I hope I don't have to jet it down. The altitude here is about 2500ft. the factory jets are 73's and the book says it is set at sea level and to come down one size for 2000ft. Any advice on that.
Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
Mark, That John is pretty fast when it comes to answers. 
I am putting the Edlebrock back on my truck for a spell. I am having trouble with the open breather fiting, and am trying to recall if I ran a spacer under it before to raise it a bit. Anyone had to do this?
John
I am putting the Edlebrock back on my truck for a spell. I am having trouble with the open breather fiting, and am trying to recall if I ran a spacer under it before to raise it a bit. Anyone had to do this?
John
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Postmaster
Joined: Nov 2001
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From: Escondido, CA
Is the breather spitting oil back at you? The guy across the street from me had the same issue with his 65. He simply put the breather on wrong. I don't have too much experience with the FE side of the house other then that. I still have a hard time with the narrow heads that use the intake manifold to complete the valve cover rail.
With your Edlebroke intake, are you refering to adding extra length to the oil filler tube or using one at all?
With your Edlebroke intake, are you refering to adding extra length to the oil filler tube or using one at all?
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