Distributer Woes?
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Freshman User
Joined: Dec 2003
Posts: 39
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From: Midvale, Idaho
Distributer Woes?
Hi everyone and thanks for all the help I have received on my 79 351M. I got it in and running good, so I thought. It ran great for about a week and now is spitting, sputtering and coughing. I know I need to rebuild Carb and retime it as it is advanced to 18 degrees. I set it at the reccommended 12 degrees and it didn't like it at all. A few of the questions I have:
I live in Idaho, about 3400 ft. do I need to make any adjustments for that?
can anyone tell me how to test the distributer vacuum advance? When I pull it loose duing timing, once I plug the line, it makes no difference in the idle of the engine.
thanks again for the help. Uncle Jesse
I live in Idaho, about 3400 ft. do I need to make any adjustments for that?
can anyone tell me how to test the distributer vacuum advance? When I pull it loose duing timing, once I plug the line, it makes no difference in the idle of the engine.
thanks again for the help. Uncle Jesse
Elder User
Joined: Sep 2003
Posts: 908
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Yes, your carb is probably jetted too rich for the altitude, unless the vehicle was bought there. I live at exactly the same altitude, and mine all run rich.
Here's a down and dirty way to tell about the vac advance. Pull the hose off the carb, wipe it clean, and suck on it with your mouth. If the can is bad, you'll pull air. Otherwise, you won't.
You can also take the cap off and verify that the breaker plate is or is not moving.
You could also substitute a piece of new hose if you're really squeamish.
Here's a down and dirty way to tell about the vac advance. Pull the hose off the carb, wipe it clean, and suck on it with your mouth. If the can is bad, you'll pull air. Otherwise, you won't.
You can also take the cap off and verify that the breaker plate is or is not moving.
You could also substitute a piece of new hose if you're really squeamish.
Senior User
Joined: Jun 2002
Posts: 193
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From: Western Slope, Colorado
I had two distributors for my 400 that had the plate seized to the shaft housing, made a big difference once they were working freely. My truck runs well with 18 degrees initial advance at 4650 feet here in Colorado. I had initially tuned the advance by ear, no pinging then checked it with a timing light and saw that it was at 18, I was concerned that this was too much advance so I asked the guy that rebuilt my engine he said at this elevation the engine could use more advance than spec and that if there was no indication of detonation that it was ok.
Thread Starter
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Freshman User
Joined: Dec 2003
Posts: 39
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From: Midvale, Idaho
well I checked the distributer, got air both directions. I will pull the carb this afternoon if I make it home anyway. I should have left it were it was and disregarded what the book specs said.
Elder User
Joined: Sep 2003
Posts: 908
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Yeah, you can run more advance at altitude. When I go down to the valley, I have to run higher octane gas unless I want to mess with the timing both ways.
Uncle Jesse, signs of too rich are black sooty deposits on the plugs, and a "stinky" exhuast.
Uncle Jesse, signs of too rich are black sooty deposits on the plugs, and a "stinky" exhuast.
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Senior User
Joined: Jun 2002
Posts: 193
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From: Western Slope, Colorado
I don't know about UncleJesse but every where I take my truck from here is up, so no backing the timing off.
As scroob said make sure your breaker plate is operating freely.
As scroob said make sure your breaker plate is operating freely.
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Joined: Mar 2004
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From: temecula
my 400 was really advanced, when i just started auto school i knew almost nothing, and my ranchero had a hard time starting when it was warm, it would crank fast and slow with every fire or a plug, i ended up puting a timeing light on it one day and found it to be at 26 degrees adv. i was shocked. i retarted it and it started and ran better. i thing my dad did that back when the truck was his, he used to run the leaded fule back when it was avalible in cali.
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Joined: Aug 2000
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From: (near) Denver USA
If you have to deal with significant changes in altitude routinely, or you just want to fine tune your ignition timing for variations in fuel quality, you can use one of the "high altitude" Duraspark II modules to set up on-the-fly ignition timing adjustment.
You can identify a HA DS2 module by its yellow strain relief "grommet," and three harness sockets (instead of two sockets like the standard blue "grommet" DS2 modules).
In the OEM application, the third harness socket was connected to a barometric pressure sensor. The HA DS2 module reads the baro sensor (variable resistance) to adjust the base ignition timing over a 15-degree range.
There were two different HA DS2 modules, one with two wires on the third socket, and one with three wires on the third socket. The two-wire version is easier to use. The part number for that version is Ford #E1AZ-12A199-A or Motorcraft #DY-297.
You can wire the HA module's third socket to a 10K linear potentiometer on the dash of your truck for driver-controlled timing adjustment.
You can identify a HA DS2 module by its yellow strain relief "grommet," and three harness sockets (instead of two sockets like the standard blue "grommet" DS2 modules).
In the OEM application, the third harness socket was connected to a barometric pressure sensor. The HA DS2 module reads the baro sensor (variable resistance) to adjust the base ignition timing over a 15-degree range.
There were two different HA DS2 modules, one with two wires on the third socket, and one with three wires on the third socket. The two-wire version is easier to use. The part number for that version is Ford #E1AZ-12A199-A or Motorcraft #DY-297.
You can wire the HA module's third socket to a 10K linear potentiometer on the dash of your truck for driver-controlled timing adjustment.