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Discussion Starter #1
Hi Team,

Long time lurker, first time poster. Ive leveraged the wealth of knowledge on this site to refresh my grandfather’s 1965 Mustang GT (many thanks).

The 4v 289 with Holley 4160 cranks and idles reliably, and now I’m trying to fine tune the timing to help her purr. Currently measuring 19” vac at the manifold, points are set with a .017 gap for a 36ish degree dwell, plugs at .035.

My question is in regards to timing. I took the #1 plug out and knocked the engine until it blew out my finger and this corresponded to the rotor in the distributor effectively lining up with correct plug position at about 1 o clock on the distributor as you’re looking towards the back of the car.

This corresponded to approximately 10-12 degrees of advance on the harmonic balancer which seems to be acceptable for an old original stock engine (Aware 6 degrees is the book answer).

I was primarily content until I put it all back together, hooked up the $50 eBay timing light to the number wire and cranked her. The light has a rotary dial on the back for advance and for me to sync up the light for my 12 degree mark, the dial reads something crazy like 35 degrees of advance. I’m a novice with the light as I’m more accustomed to the old school method of timing.

I haven’t loosened the distributor again to tweak it in the worry that the light is crap or some very likely form of operator error.

Am I overthinking and imagining a problem? Can the harmonic balancer (which I did not install or tweak) be installed incorrectly where the markings aren’t accurate? Which method do y’all trust more? TIA
 

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Sounds like you need to verify if the outer ring on the harmonic balancer has slipped on the rubber bushing. You can verify with a piston stop in the #1 cylinder and bring it to top dead center and see if the marks line up. Could also be a mismatch parts on the balancer to timing pointer on the cover.
 

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Did you remove and plug the vacuum advance line from the distributor before checking the timing?
 

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Did you remove and plug the vacuum advance line from the distributor before checking the timing?
After checking all the things posted & they seem fine put a socket and pull handle on the front crank bolt & rock the crank slightly back& forth while watching the rotor ( with cap off) to see if the timing chain may be stretched. If it's not streched the rotor will move with the crank immediately when you change directions. . .................. Also if you're running points you really need a dwell meter to check the points dwell then set your timing per repair manual. .......Yeah it's a pain I know . Don't know what brand points are being used today but I always had better luck useing Blue Steak points in the old Flathead engs ,Fe & windsors.
 

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Hi Team,

Long time lurker, first time poster. Ive leveraged the wealth of knowledge on this site to refresh my grandfather’s 1965 Mustang GT (many thanks).

The 4v 289 with Holley 4160 cranks and idles reliably, and now I’m trying to fine tune the timing to help her purr. Currently measuring 19” vac at the manifold, points are set with a .017 gap for a 36ish degree dwell, plugs at .035.

My question is in regards to timing. I took the #1 plug out and knocked the engine until it blew out my finger and this corresponded to the rotor in the distributor effectively lining up with correct plug position at about 1 o clock on the distributor as you’re looking towards the back of the car.

This corresponded to approximately 10-12 degrees of advance on the harmonic balancer which seems to be acceptable for an old original stock engine (Aware 6 degrees is the book answer).

I was primarily content until I put it all back together, hooked up the $50 eBay timing light to the number wire and cranked her. The light has a rotary dial on the back for advance and for me to sync up the light for my 12 degree mark, the dial reads something crazy like 35 degrees of advance. I’m a novice with the light as I’m more accustomed to the old school method of timing.

I haven’t loosened the distributor again to tweak it in the worry that the light is crap or some very likely form of operator error.

Am I overthinking and imagining a problem? Can the harmonic balancer (which I did not install or tweak) be installed incorrectly where the markings aren’t accurate? Which method do y’all trust more? TIA
Since the engine is no longer stock and today's fuels aren't what they were when the specs were printed, the published static timing number is simply a "guess". Run as much spark advance as the engine will tolerate without "pinging". Once you do that you can mark the balancer for a reference when doing future tune-ups. Remember that dwell affects timing so check and adjust timing after servicing the points.
 

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I agree with erials. Sounds like the most likely thing is you are measuring a combination of initial timing and vacuum advance.

The timing you are trying to measure is just initial timing.

Although I am unfamiliar with your timing light...another way to get close is to hook to #1 wire. Rotate engine to 10 degree mark on pointer. Loosen distributor and play with it until you can figure out exactly how to get the timing light flashing at the point the distributor rotor is sitting....then lock it down. For this test the ignition is "ON" but engine is not running.

Phil
 

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Discussion Starter #7
Hey team,
Follow up, took a week to get away from daddy duties but the source of my frustration came in the form of rookie operator error. I left the vacuum advance connected which threw off my timing light measurements.

New favor to ask from the experts (problem is high idle):

With the vacuum advance disconnected the engine’s sweet spot is between 9-12 degrees. 9 degrees idles around 850-900 rpm’s. 12 degrees provides an increased manifold vacuum reading and the idle is closer to 1000 rpm (no tachometer, both measured with a multimeter at the neg side of the coil, car in PARK).

In both cases when I connect the vacuum advance it jumps to 1400ish and it sounds like it’s racing. Idle screw at the carb as all the slack taken out.

Sign of bad/overactive vacuum advance? Any tweaking I can do to that connection at the distributor? Any options left for me to bring down the idle rpm? TIA
 

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OK, where is the other end of the vacuum advance line connected?
 

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Discussion Starter #9
Good call, should have prefaced. Manifold vacuum port at the base of the Holley on the front passenger side. Tried the ported vacuum location at the passenger side metering block without much of an audible change. It needs the full vacuum port, right?

As an aside, did a neighborhood test drive. It’s idling high but it’s not trying to pull away at a stop sign. Surely I’m missing something elementary.
 

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Use the ported vacuum on the side of the metering plate. That's the factory-specified connection on Ford engines. Should be little or no vacuum at all at idle.
764476
 

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I always set my timing by the WOT method. I always carry a 1/2" wrench with me. Adjust timing so you are set just before getting pinging at WOT. To this day I could not tell you were my initial timing is. (Flame suit on.)
 

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I always set my timing by the WOT method. I always carry a 1/2" wrench with me. Adjust timing so you are set just before getting pinging at WOT. To this day I could not tell you were my initial timing is. (Flame suit on.)
No suit required. I always start at factory spec, then hit the road (or a big parking lot) and open the the throttle too far at low rpm. If it doesn't ping, I advance 2° (using a timing light) until it does. Then I back off 2°. This gives best power, and best fuel economy. I do, however, know what the setting is, because after you have done this once, on a particular engine, it doesn't change. I know, for example, that my 289HP sets at 14°BTDC at idle. No need to repeat the ping test, because that's where it will end up.

Adjusting the points will always change the timing, so I know that if I set the points for exactly 33° dwell, the timing will go right to 14°BTDC.
 

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Good call, should have prefaced. Manifold vacuum port at the base of the Holley on the front passenger side. Tried the ported vacuum location at the passenger side metering block without much of an audible change. It needs the full vacuum port, right?

As an aside, did a neighborhood test drive. It’s idling high but it’s not trying to pull away at a stop sign. Surely I’m missing something elementary.
Even with the vacuum advance connected to a full manifold vacuum source you should be able to control the idle speed by closing the throttle plates to limit the amount of air and fuel being fed to the engine. If you can not reduce the idle speed by way of the curb idle screw then you have a vacuum leak somewhere... either externally at a hose, gasket or connection or "internally" past the primary or secondary throttle plates.
 

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No suit required. I always start at factory spec, then hit the road (or a big parking lot) and open the the throttle too far at low rpm. If it doesn't ping, I advance 2° (using a timing light) until it does. Then I back off 2°. This gives best power, and best fuel economy. I do, however, know what the setting is, because after you have done this once, on a particular engine, it doesn't change. I know, for example, that my 289HP sets at 14°BTDC at idle. No need to repeat the ping test, because that's where it will end up.

Adjusting the points will always change the timing, so I know that if I set the points for exactly 33° dwell, the timing will go right to 14°BTDC.
I have Pertronix on the one, so the timing never changes. When my timing light quit working years and years ago, I was a poor student. I just learned to live without it.
 

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I have Pertronix on the one, so the timing never changes. When my timing light quit working years and years ago, I was a poor student. I just learned to live without it.
If the initial timing was set right then, it is still set.
 

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Good call, should have prefaced. Manifold vacuum port at the base of the Holley on the front passenger side. Tried the ported vacuum location at the passenger side metering block without much of an audible change. It needs the full vacuum port, right?

As an aside, did a neighborhood test drive. It’s idling high but it’s not trying to pull away at a stop sign. Surely I’m missing something elementary.
Well, he hasn't got back to us. By this description, he has the vacuum advance connected incorrectly.
 

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Well, he hasn't got back to us. By this description, he has the vacuum advance connected incorrectly.
"Incorrect" only as it applies to how it left the factory. The use of ported spark was really just a method of using the increased exhaust gas temperature at closed throttle to reduce hydrocarbon emissions. Connecting the vacuum advance to a manifold vacuum source will do a couple things:

1. Provide a much smoother idle.
2. Reduce exhaust gas temperature leading to lower under-hood and engine coolant temperatures.

Yes, some minor tuning may be needed after this change as would be required after any modification.
 

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Discussion Starter #19
Thanks for all the feedback team, usually have my hands full with the rug rays so I have to make deals with the devil to sneak out to the garage during naps. Tracking on most of the pros v cons for ported vs full vac based on other threads. Swapped it over to ported vacuum, verified it has a zero vac reading at idle then that it increased when the throttle opened so I can confirm the port is clear and the vacuum canister is operating as advertised. So I’m satisfied with timing and vacuum measurements between 9 and 12 degrees without the advance. Vacuum is between 17 and 19 during this litany of tests both at the back of the manifold and at the bottom front port of the carb without fluctuations so I don’t suspect much of a leak but that’s not to say there isn’t one. I’m new to the engine so I’m still calibrating my ear. Going to play with the choke setting, fast idle screw, and finally curb idle screw to hopefully change the setting of the throttle plates a bit (curb idle screw is effectively all the way out so I think the plates might be open too much at its baseline setting of the choke is off).
Wouldn’t be able to narrow this down without all the great cajoling and spitballing from the pros here. Thanks for helping me breathe new life into the 65 and I’ll keep y’all updated. Moving front to back systematically so I’m sure there will be a host of to-dos once I get on the other side of the firewall.
 
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