Distributer help needed
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Freshman User
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Distributer help needed
I have a 1970 crewcab w/390 auto. I had a new distributer installed by a shop. They didn't hook up the vaccume advance saying that it advanced plenty without it and it advanced to far with it. I guess that leaves me to recurve it or have it recurved. It runs great but I keep thinking that it should have more low end, I pull a horse trailer with it. Is this a fix I should do or leave it to the big boys or leave it alone? I recently did a road trip and got over 11 miles to the gallon, I was tickled with that. can I get more?
Elder User
Joined: Jul 2002
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From: Charlotte
Was the shop not able to recurve it? I am amazed that they would give it to you with the vacuum advance disconnected.
Was the 11 mpg pulling the trailer? If so, that really isn't too bad. I get 14/16 with a stepside no trailer.
Was the 11 mpg pulling the trailer? If so, that really isn't too bad. I get 14/16 with a stepside no trailer.
Senior User
Joined: Sep 2006
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From: Newbury Park Ca.
"It advanced too far with it" tells the story. Apparently this "shop" is un aware of how to modify the mechanical advance on these old distributors. I'm betting if you hook it up it will ping under a load and they couldn't correct that so they disconected the vac instead of fixing the mechanical curve. I've seen everything from this "fix" to expensive water vapor injection systems installed in an effort to eliminate the pinging, when all it needs is proper initial setting, and a little tweeking of the mechanical spring anchors to limit the max advance. But then again, I don't know anything about curving a distributor, or the effects a carb port has on the vacuum advance..........aMP
Logistics Pro
Joined: Oct 2005
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From: Mddl A MexCans
LOL, ahhh shiattt I sense some therapy in the future LMAO... Come to think of it I myself would like to get a better understanding of this vac advance mistery. Anyone care to add a link or write up a procedure. Soon I will have the beast back together and would love a step by step for he initial checkup after breakin.
Senior User
Joined: Sep 2006
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From: Newbury Park Ca.
You didn't mention if this "new" dist. was a stocker or a hotsy totsy aftermarket deal. If it is an aftermarket unit it is possible the mechanical portion WAS curved to your application by the "shop". Possible, but un likely. Did they supply you with a curve sheet? Or just slap in a replacement dist from a local parts store? GM distributors are easy and obvious, the old Fords are quite different when it comes to modifications and dialing in to the vehicle. Again, it is not un common to block off the vac adv on the aftermarket units, as they have a very adjustable mechanical adv mechanism. If you feel the bottom end could be better, try kicking the initial a couple of degrees and see if it improves without pinging under load. A ballpark setting is to advance it until it pings on the gas (octane) you will be running, then back it off until it quits pinging. This isn't scientific, but just a place to start. .......aMP
PS: Remember these vehicles, (older) were designed to run on leaded fuel and tuning them to run on un leaded can be tricky........
PS: Remember these vehicles, (older) were designed to run on leaded fuel and tuning them to run on un leaded can be tricky........
Post Fiend
Joined: Mar 2004
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From: Union, Washington
Vacuum advance, when connectted to the "Ported Vacuum" source only adds advance when the engine is under light load. This condition, light load and moderate RPMs, allows the engine to tolerate additional ignition timing above the 34° to 38° normally assumed to be max. This aditional timing improves fuel economy. I have seen engines tolerate as much as 50+ degrees of timing under these conitions. Using manifold vacuum as your vacuum source will not do the same as using the ported vacuum source. The "Ported Vacuum" source is located in the carburator above the throttle plates and does not see total manifold vacuum at low throttle settings and none at idle (if the carb is set up properly).
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Freshman User
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I figure on doing some tweaking to the Dist. I'm not sure what I'll run into under the plate . Sounds like I can bend something or maybe heavier springs are in order. I'm getting no ping now ( can't remeber where it is set) but when I plug in the v/a she pings on a pull.
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Freshman User
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The "new" Dist. is a stocker I'm sure. Something from NAPA. I don't know what "initial" is.
Should I set it to ping at idle then back it off (without the v/a plugged in)? I can't remember the procedure but I believe I set it to facory specs w/o the v/a plugged in. Plugged in the v/a and hit the road, all was fine til I started up a hill. I pulled over and retarded it some and it pingged on the next hill. I unplugged the v/a and no more ping. I advanced it some after I unplugged the v/a just for giggles, still no ping. I have no idea where it is set now.
Should I set it to ping at idle then back it off (without the v/a plugged in)? I can't remember the procedure but I believe I set it to facory specs w/o the v/a plugged in. Plugged in the v/a and hit the road, all was fine til I started up a hill. I pulled over and retarded it some and it pingged on the next hill. I unplugged the v/a and no more ping. I advanced it some after I unplugged the v/a just for giggles, still no ping. I have no idea where it is set now.
Elder User
Joined: Apr 2004
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Find a shop that has a distributor machine and an old guy who runs it, have it calibratered to Fords specs and set the timing on install to the specs called for.
This will let the engine live a lot longer than guessing at the advance curve. I hate
to say this but some of the younger guys don't have much of a clue about distributors. My 2 cents.
This will let the engine live a lot longer than guessing at the advance curve. I hate
to say this but some of the younger guys don't have much of a clue about distributors. My 2 cents.
Senior User
Joined: Sep 2006
Posts: 162
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From: Newbury Park Ca.
Yes you can "bend" the spring anchors to limit, or control the amount of mechanical advance, but, you should put a light on it to see where initial is set, and how much advance you get as the Rs come up, with and without the VA hooked up. I would HIGHLY recomend that you limit your's well below the 50* mentioned above, unless you own stock in a piston company. But then again, I have no idea what I'm talking about..............aMP
Elder User
Joined: Jun 2001
Posts: 508
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From: Corpus Christi, Texas
It sounds like you have a stock duraspark distributor. I am running one with the vacuum advance not hooked up. But I have recurved mine with changing some pieces in it to keep it from advancing any more than a total of 16 degrees. I also changed the springs in mine to get total advance at 2000 rpms. Most ot the over the shelf Fe Duraspark distributors come with strong springs and the "T" looking piece that allows the engine to advance to much on the mechanical side, which inturn lets you vacuum advacne vadvance your engine to much. you cancan change out the vaccuum advance to an adjustable one or just recurve your mechanical with different springs. than i would hook the vacuum advance up to manifold vacuum because you will have vacuum all the time. But here is a website that might help you.
http://www.bob2000.com/dist.htm
http://www.bob2000.com/dist.htm
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
This is for the Dura-spark electronics dist., but the plate screws down the same and everything underneath is the same.
http://www.reincarnation-automotive....ons_index.html
http://www.reincarnation-automotive....ons_index.html
