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 Demon 750 calibration on a 428 Ford FE 
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Joined: Sun Oct 25, 2015 7:39 pm
Posts: 21
GNTKLLR wrote:
Since I need to limit my Duraspark's amount of vacuum advance as well, because it's travel is far too much and I've already adjusted it's diaphragm spring to limit it, (I've put it on the back burner, but am reminded each time upon very light acceleration approaching the top of each gear, some pinging) I'd appreciate it if you'd share your idea/s for doing that.



There is a slot in the arm where it leaves the diaphragm of the assembly. I drilled a 3/32" hole from the surface where the two retaining screws are through this slot near the diaphragm body and installed a 3/32" roll pin. This limited vacuum advance from 24° to 15°.


Wed May 24, 2017 11:35 pm
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Joined: Sun Oct 23, 2016 5:52 pm
Posts: 133
Location: Canada
Roadknee wrote:
GNTKLLR wrote:
Since I need to limit my Duraspark's amount of vacuum advance as well, because it's travel is far too much and I've already adjusted it's diaphragm spring to limit it, (I've put it on the back burner, but am reminded each time upon very light acceleration approaching the top of each gear, some pinging) I'd appreciate it if you'd share your idea/s for doing that.



There is a slot in the arm where it leaves the diaphragm of the assembly. I drilled a 3/32" hole from the surface where the two retaining screws are through this slot near the diaphragm body and installed a 3/32" roll pin. This limited vacuum advance from 24° to 15°.


Thank you for that. :thumbr: I'll get a better look and doing that or something like that with this one.

_________________
Mike

1986 Mustang convertible. Originally 3.8L V6 with EEC-IV CFI.
Now has a Holley List-4412-2, and averages 32 (27 US) MPG.
If you're ever bored - some narrow band O2 tuning video of this thing:
http://www.youtube.com/channel/UC9glRIa3jAAtNhaXfg_cZXQ


Fri May 26, 2017 12:54 am
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Joined: Sun Oct 25, 2015 7:39 pm
Posts: 21
A few mornings ago I turn the key on the Ford and it won't start. I check the resistance across the new magnetic pickup and it reads 27 ohms. Spec is 400 ohms minimum. I figure the early failure and the fact I had to reverse the wires into the MSD box must be related. I have another pickup to install so I remove the failed one from the distributor. With the two side by side I pull a magnet from the tool box and place it near the top of the failed pickup. The magnet is repulsed. I place the magnet next to the spare pickup and it is attracted. I install the spare pickup, reverse the wires to the correct orientation and assemble the distributor. I turn the key and it fired right up. The brand new Standard Motor Products magnetic pickup was defective (magnet installed upside down) right out of the box. I wonder how many of them were mass produced this way.

Good news is the motor runs better than ever. I even connected vacuum advance to manifold vacuum. There is only enough vacuum to pull about 10 degrees of 15 available (abut 33 degrees idle timing now) and it bounces around some with the lumpy cam but seems to idle better than when connected to ported vacuum. Definitely idles better than 15° with the original MSD distributor.


Fri May 26, 2017 7:46 am
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Joined: Mon Dec 01, 2014 7:38 pm
Posts: 125
GNTKLLR wrote:
Roadknee wrote:
GNTKLLR wrote:
Since I need to limit my Duraspark's amount of vacuum advance as well, because it's travel is far too much and I've already adjusted it's diaphragm spring to limit it, (I've put it on the back burner, but am reminded each time upon very light acceleration approaching the top of each gear, some pinging) I'd appreciate it if you'd share your idea/s for doing that.



There is a slot in the arm where it leaves the diaphragm of the assembly. I drilled a 3/32" hole from the surface where the two retaining screws are through this slot near the diaphragm body and installed a 3/32" roll pin. This limited vacuum advance from 24° to 15°.


Thank you for that. :thumbr: I'll get a better look and doing that or something like that with this one.


X2 on the roll pin, I did the same on my vacuum advance canister. If you look on the (VAC)vacuum advance canister's arm you may/will see a number stamped into it, this number is 1/2 the maximum total ignition vacuum advance the VAC will produce(this really depends on what total vacuum the engine makes, but over 20 in will usually give the maximum vacuum advance). If the roll pin method does not work out, you can purchase a VAC for a '74 F100 w/390, this canister gives a max vacuum advance of 12 degrees(#6 stamped on the arm). I looked and researched for any info regarding Duraspark vacuum advance canisters, high and low, really not much out there compared to the COMPLETE VAC listings of a GM product that are floating around the internet. I really liked the older Ford VAC's that had the removable front port that allowed shims/washers to be installed to limit the amount of advance. Hope this helps.


Fri May 26, 2017 8:23 am
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Joined: Sun Oct 23, 2016 5:52 pm
Posts: 133
Location: Canada
Roadknee wrote:
A few mornings ago I turn the key on the Ford and it won't start. I check the resistance across the new magnetic pickup and it reads 27 ohms. Spec is 400 ohms minimum. I figure the early failure and the fact I had to reverse the wires into the MSD box must be related. I have another pickup to install so I remove the failed one from the distributor. With the two side by side I pull a magnet from the tool box and place it near the top of the failed pickup. The magnet is repulsed. I place the magnet next to the spare pickup and it is attracted. I install the spare pickup, reverse the wires to the correct orientation and assemble the distributor. I turn the key and it fired right up. The brand new Standard Motor Products magnetic pickup was defective (magnet installed upside down) right out of the box. I wonder how many of them were mass produced this way.

Good news is the motor runs better than ever. I even connected vacuum advance to manifold vacuum. There is only enough vacuum to pull about 10 degrees of 15 available (abut 33 degrees idle timing now) and it bounces around some with the lumpy cam but seems to idle better than when connected to ported vacuum. Definitely idles better than 15° with the original MSD distributor.


Good grief! We really cannot assume anything is manufactured correctly anymore.

:thumbr:

_________________
Mike

1986 Mustang convertible. Originally 3.8L V6 with EEC-IV CFI.
Now has a Holley List-4412-2, and averages 32 (27 US) MPG.
If you're ever bored - some narrow band O2 tuning video of this thing:
http://www.youtube.com/channel/UC9glRIa3jAAtNhaXfg_cZXQ


Fri May 26, 2017 10:04 pm
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Joined: Sun Oct 23, 2016 5:52 pm
Posts: 133
Location: Canada
aquartlow wrote:
X2 on the roll pin, I did the same on my vacuum advance canister. If you look on the (VAC)vacuum advance canister's arm you may/will see a number stamped into it, this number is 1/2 the maximum total ignition vacuum advance the VAC will produce(this really depends on what total vacuum the engine makes, but over 20 in will usually give the maximum vacuum advance). If the roll pin method does not work out, you can purchase a VAC for a '74 F100 w/390, this canister gives a max vacuum advance of 12 degrees(#6 stamped on the arm). I looked and researched for any info regarding Duraspark vacuum advance canisters, high and low, really not much out there compared to the COMPLETE VAC listings of a GM product that are floating around the internet. I really liked the older Ford VAC's that had the removable front port that allowed shims/washers to be installed to limit the amount of advance. Hope this helps.


Great tip on the '74 F100 390 unit, thank you :thumbr:

_________________
Mike

1986 Mustang convertible. Originally 3.8L V6 with EEC-IV CFI.
Now has a Holley List-4412-2, and averages 32 (27 US) MPG.
If you're ever bored - some narrow band O2 tuning video of this thing:
http://www.youtube.com/channel/UC9glRIa3jAAtNhaXfg_cZXQ


Fri May 26, 2017 10:17 pm
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Joined: Mon Apr 17, 2017 6:57 pm
Posts: 4
In the future if you are using a Duraspark distributor and an MSD ignition box, just get the MSD connector 8869, it connects everything with no cutting. Well worth the $18 to not have to cut/resplice all of that.


Mon May 29, 2017 9:00 am
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