Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166067
10/01/16 07:32 PM
10/01/16 07:32 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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Temporarily disconnect the vacuum advance. Back the timing off from 27 until it does start OK when hot. Whatever number that is, probably around 18 degrees, is where your initial needs to go. You probably have a stock distributor with way too much mechanical advance if it goes to 52 with the vac advance plugged. Since your total timing still needs to be 34, that means you have to modify the distributor so its total advance is 34-18 or only 16 degrees. I recommend one of these: http://www.4secondsflat.com/Mopar%20Mechanical%20timing%20limiter%20plate.htmFar easier than welding up and filing the slots.
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Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166153
10/01/16 10:23 PM
10/01/16 10:23 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I would get max manifold vacuum all the while reducing your idle speed to the lowest stable hot idle speed in gear (which is what you will see stoplight to stoplight) or neutral if a stick, that you can achieve then reduce the INITIAL till the VACUUM drops 1 in hg and at that vacuum point your initial timing is ideal. if it will not crank when hot then reduce the INITIAL (1) degree & retry, then another degree if needed OR keep it where it was first at & wire in a NC momentary closed contact switch to the ign switch "ign2" terminal/circuit & push the button then get it cranking with the ign key then release the button while still cranking. As said get the FBO $22 plate, it is the best deal going by far & use it to set the total (initial+slots) & I would set the total to 35 with open chambered heads and 31 with mag heads which will be very close to ideal. I had 18 on a bone stock 80's 318 2bbl. holler what you end up with. EDIT then work with springs then plug in work with the can (if used). you want the springs to start advancing ~100-200 RPM above the hot in gear idle speed you have
Last edited by RapidRobert; 10/01/16 10:49 PM. Reason: more info
live every 24 hour block of time like it's your last day on earth
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Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166169
10/01/16 10:51 PM
10/01/16 10:51 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Should I still run vacuum advance on the distributor or block it off. street, street/strip or strip
live every 24 hour block of time like it's your last day on earth
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Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166175
10/01/16 11:03 PM
10/01/16 11:03 PM
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Joined: Jan 2003
Posts: 5,789 Hamilton, Ontario Canada
Magnum
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master
Joined: Jan 2003
Posts: 5,789
Hamilton, Ontario Canada
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We see this over and over on big cammed engines. The engine wants timing at idle to be somewhere north of 20 deg but the engine will not start.
So the timing is pulled back to allow the engine to start but the torque at tip in is reduced, it doesn't idle as good, throttle response is reduced and the mileage falls off.
Vacuum advance or computerized ignition control is the only way to have both.
For ignition timing you need to control at least 4 things, timing at cranking, idle, cruise and wide open throttle.
69 Super Bee, 93 Mustang LX, 04 Allure Super
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Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166292
10/02/16 04:00 AM
10/02/16 04:00 AM
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Joined: Mar 2005
Posts: 1,545 Seattle, WA
375inStroke
Special needs person
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Special needs person
Joined: Mar 2005
Posts: 1,545
Seattle, WA
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You need lighter advance springs. The timing is lower when cranking, but once running, the springs are light enough to allow mechanical advance to kick in at idle. Since mechanical is already operating at idle, there is less available at higher rpm, so your total won't be so high. http://www.manciniracing.com/malidiadspse.html
Last edited by 375inStroke; 10/02/16 04:00 AM.
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Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166367
10/02/16 11:58 AM
10/02/16 11:58 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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The plan is to drive the car on the street I would set the initial then limit the total (initial+slots) to 35 with that plate then toss the heavy spring with the elongated loop & sub in a mr gasket or MP light spring in its place for a start & mix and match springs so you are just under the pinging point at WOT up thru the gears on your hottest/driest day (dont crowd that line too close but you want to be fairly close to it & any ping you can hear is WAY too much) then adj the can with a 3/32 allen wrench, same deal staying under the pinging point in everyday driving under varying load (in hg) and RPM conditions. CCW slows the rate. also on the springs you dont want it to start advancing any less than 1-200RPM below your hot idle speed is (no mech adv at idle), IE idle at 700, advance starts at 850
live every 24 hour block of time like it's your last day on earth
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Re: Setting Timing With Vacuum Gauge
[Re: 375inStroke]
#2166423
10/02/16 01:51 PM
10/02/16 01:51 PM
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Joined: Apr 2006
Posts: 4,220 West Plains, MO
DrCharles
master
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master
Joined: Apr 2006
Posts: 4,220
West Plains, MO
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You need lighter advance springs. The timing is lower when cranking, but once running, the springs are light enough to allow mechanical advance to kick in at idle. Since mechanical is already operating at idle, there is less available at higher rpm, so your total won't be so high. He'll never get a stable idle if he does that, unless the advance is all in at idle (which is no good for the street). If the advance is already operating, more timing = faster idle, more timing... put it in gear, slower idle, less timing, slower idle, etc.
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Re: Setting Timing With Vacuum Gauge
[Re: ringo440]
#2166472
10/02/16 02:54 PM
10/02/16 02:54 PM
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Joined: Jul 2013
Posts: 1,272 Northern Calyfornua
Sxrxrnr
pro stock
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pro stock
Joined: Jul 2013
Posts: 1,272
Northern Calyfornua
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Vaccumn guage readings are often much more impacted by other than ignition timing,,,vacuum leaks, defective carbs, carb settings, leaky cylinders, plug wires, idle speed, the list goes on.
It is a very rough, but complementary troubleshooting and tuning tool.
Relying on a vacuum guage to set timing is not the method that I would subscribe to. I prefer a digital set back timing light at a minimum.
The point being that you may have issues other than timing that you are dealing with that too must be explored.
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