Re: vacuum advance
[Re: can.al]
#1019093
06/23/11 04:30 PM
06/23/11 04:30 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I use it, better mileage/keeps plugs cleaner. I do not have a specific build in mind but it does take alot of work to get spot on. 3/32" allen wrench to change when (in hg) the slope starts (easy) & soldering strips of feeler gauge on the back side of the can to limit the total amt of adv (hard)
live every 24 hour block of time like it's your last day on earth
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Re: vacuum advance
[Re: can.al]
#1019096
06/24/11 12:10 AM
06/24/11 12:10 AM
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Joined: Jan 2007
Posts: 780 Woodinville, WA
Viol8r
super stock
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super stock
Joined: Jan 2007
Posts: 780
Woodinville, WA
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Quote:
..vac advance has other benefits. engine runs cleaner,more efficient,cooler and makes more power at cruz. at wot it will have no effect.
Sounds like you got things figured out!
11:1 440......550hp. No vacuum advance here.
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Re: vacuum advance
[Re: can.al]
#1019098
06/24/11 05:51 AM
06/24/11 05:51 AM
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Joined: Apr 2008
Posts: 90 NL
Frederick
member
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member
Joined: Apr 2008
Posts: 90
NL
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If you can, use it. It has benefits, like mentioned before.
However, if you have a large cam, the vacuum will fluctuate too much, causing the timing to go all over the place. Not good for fuel economy or the engine. In this case you'd run locked timing.
Last edited by Frederick; 06/24/11 08:48 AM.
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Re: vacuum advance
[Re: Frederick]
#1019099
06/24/11 07:37 AM
06/24/11 07:37 AM
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Joined: Oct 2003
Posts: 21,345 Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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I've also heard they can be slow to respond to vacuum, like when you go from cruise to WOT...giving you way too much vacuum at WOT, if you have an aggressive base tune due to a lopey cam. Plus, if you adjust the mechanical advance so that it's all in at a lower RPM, then you need less vacuum advance
with the performance oriented distributors that don't have vacuum advance, should tell you that it's not critical to have it.
run it if you want, leave it unhooked if you don't.
for what it's worth, my Dakota with EFI never gives more than 38-39 degrees of total timing. apparently the magnum head design doesn't require the advance that older heads do.
**Photobucket sucks**
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Re: vacuum advance
[Re: LAR_414]
#1019104
06/24/11 10:44 AM
06/24/11 10:44 AM
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Joined: May 2005
Posts: 4,749 Florida
BDW
master
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master
Joined: May 2005
Posts: 4,749
Florida
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Quote:
15.5 MPG with a low 11 second 3400lbs 550hp car on pump gas!
What kind of gears / OD?
I've got a mild 340 with 3.73's that only gets 12mpg
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Re: vacuum advance
[Re: LAR_414]
#1019106
06/24/11 05:33 PM
06/24/11 05:33 PM
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Joined: Jan 2003
Posts: 2,253 New York
rarefish
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,253
New York
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Not to hijack the post but, I'm getting a slight surging when driving under a light load at part throttle. A friend told me to disconnect the vacuum advance and that should solve the problem. Have not tried it yet, but does that sound right? The car is a bone stock 68 Charger R/T. I checked the timing and found that I have 14 degs at 650 rpm. A total of 34 degs mechanical advance. Not sure at what RPM and with the vacuum reconnected I get a total of 53 degs advance. The car runs good other wise and does not ping.
Last edited by rarefish; 06/25/11 11:01 PM.
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Re: vacuum advance
[Re: rarefish]
#1019107
06/24/11 06:36 PM
06/24/11 06:36 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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block the metering rods all the way up on the power step & take it back out for a spin/holler back
live every 24 hour block of time like it's your last day on earth
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Re: vacuum advance
[Re: can.al]
#1019109
06/25/11 01:31 AM
06/25/11 01:31 AM
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Joined: Jul 2005
Posts: 1,472 Overland Park, KS.
Joshs68
pro stock
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pro stock
Joined: Jul 2005
Posts: 1,472
Overland Park, KS.
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10.5/1 470 w [Email]265@.050[/Email] I run 20* initial w 35* total. No vaccuum advance. I am also using an FBO setup distributor and would reccommend him to anybody. He removed the vac mechanism on my dist and it came setup for a great price. Dropped in and works great.
Last edited by Joshs68; 06/25/11 03:46 AM.
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Re: vacuum advance
[Re: rarefish]
#1019110
06/25/11 06:11 PM
06/25/11 06:11 PM
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Joined: Apr 2008
Posts: 90 NL
Frederick
member
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member
Joined: Apr 2008
Posts: 90
NL
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Quote:
Not to hijack the post but, I'm getting a slight surging when driving under a light load at part throttle. A friend told me to disconnect the vacuum advance and that should solve the problem. Have not tried it yet, but does that sound right? The car is a bone stock 68 Charger R/T. I checked the timing and found that I have 14 degs at 650 rpm. A total of 43 degs mechanical advance. Not sure at what RPM and with the vacuum reconnected I get a total of 53 degs advance. The car runs good other wise and does not ping.
43 Total is too much, it should be around 35 with stock heads. It's most likely stumbling because of too much advance, plugging the vacuum advance would solve it, but isn't really the right way to do it. I suggest you plug off the vacuum advance, check if the stumble is gone.
-If it is, limit the total mechanical advance to 35deg by welding up the advance slot. (Trial and error, should be all in by 3000rpm) Then re-attach the vacuum advance.
-On the other hand if the stumble isn't gone, it either needs more advance taken out, or the mixture is too lean.
Cheers
Fred
383B, 9.8:1, Lunati 60302(220/226@0.050 262/268Dur, 0.475"/0.494", Stealth heads, Performer manifold, QF SS-750-AN carb, 3.31Diff, A833 4-speed manual.
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