New Duraspark install, working but needs perfection.
 

Hello ford gurus! I have a 1985 Ford F150 300 6 and just performed a Duraspark Conversion which seems to be working. The truck is running anyways. I got rid of all the emissions junk and have an older carb and a vacuum advance distributor working with the blue grommet ignition module. New wires for the distriubutor. I need to thank everyone here for all the amazing info I have absorbed. This would not have been possible without you guys.

Everything sounds and feels smooth although so far I have only set the distributor by ear. I do seem to be getting extremely low milage, like 1-3 mpg, so I know that I need to get in there and time the distributor. Are there other adjustments that I need to do? Do I need to switch out the old spark plugs as well, and if so what should the gap be?

Here is an article I found. At the bottom of the page they talk about switching the springs in distributors to adjust the curve the which I would like to try (using mr gasket #925D spring kit). I am not sure if this applies to the 300 6 engine or only the smaller 200/250 engines.

Classic Inlines - Duraspark II Swap

I was also wondering if there is a chance I have a bad ignition module. The one I got says "switches" on it (it does have the blue grommet) and was new in the box off of ebay. I have a back up that came from the junkyard and says duraspark on it. If the module was not working, would the engine still start?

So yeah, trying to optimize my install now and on my knees for your help.

The duraspark is your module, if there was a problem with that you wont run.
sounds like the timing is way off. quick way to set it is to advance it till she starts to ping than back her off a few degree's with the vacuum disconnected, the advance spring kit is allways a good idea to dial in the distributor to perfection, but your fuel millage is worrying me abit it should be doing better than that unless your way off on your timing. Give it a shot and let us know how its working David7.3

The Ford dist is very difficult to change the springs inside(at least the v8's are). If you can get on a site where someone has already experimented and has a recommended setup go for it. But if you are going to come up with your own curve it takes a lot of experimentation and tearing the dist down many times to get it just right.

I can't believe it's running good and only getting 1-3mpg. Something is wrong with your figuring on the mileage, or it's not running very good.

As Dave said it requires a lot of disassembly and would need to be done multiple times to get it right.

The Rein'car'nation website has illustrated instructions for recurving your DSII distributor.
Duraspark_distributor_recurve_instructions_index
There are instructions on how to test your spring/slot combinations in the Crane Cams adjustable vacuum advance pdf.
http://www.cranecams.com/uploads/ins...2e_%281%29.pdf

This is a low revving truck, not a lightweight drag car.
I could understand 13mpg, but 1-3 mpg seems like all your plugs would be wet and black smoke would be pouring out the exhaust.

I don't even see that kind of mileage with a blown powervalve in my 460 truck and it is so rich it burns your eyes.

When I bought my 1986 F150 with 4.9L engine, there were many vacuum leaks, and the computer was in the "safe" mode, where the ignition timing is locked as well as the carburetor being in its richest mode. The truck bucked like a bronco! Even at that point, the mileage was 8-11 mpg.

After DS conversion, 6 years of recorded mileage reveals 17-22 mpg. Keep looking... something is wrong!

The 3 step scenario of a failing DuraSpark ignition module:

1) Module overheats, engine dies. Module cools down, engine restarts almost as once.

2) Module overheats, engine dies. Module cools down, engine restarts in an hour...or so.

3) Sooner or later, usually sooner, the module overheats, BURNS OUT. Now the engine will not restart.

Engine heat, especially radiating from the V8's red hot left exhaust manifold, is the mortal enemy of these modules.

Thru 1986, module located on left fender inner apron, just in front of firewall. If replacing, use some washers to space it further away from the apron. The more airflow around the little charmer .. the better.

And, since these modules usually fail when they overheat, taking it to an autoparts store to be tested: Will test OK unless the little charmer has burned out.

In the 1970's, DuraSpark modules were soooo unreliable...that Ford techs referred to them as NeverSpark!

Genuine Ford blue module will be marked MOTORCRAFT and/or DuraSpark and have ID numbers marked on it.

ID numbers depend on which module it is, as the original 1976 part number has been replaced multiple times.

1U2Z-12A199-AA (replaced D6AZ-12A199-B ~ D7AZ-12A199-B ~ D9VZ-12A199-A) .. Ignition Module-Blue (Motorcraft DY-893).

12A199: See the two parts catalog applications below for the various ID numbers marked on the above modules.

That is very good to know the various ways a module will fail. I don't think I have a problem with that. It starts fine and runs until it is out of gas. Still haven't had the time to time the bugger with a light. I will report back when I do. The exhaust is clean though, no gassy white or blue smoke, which there was lots of before the duraspark conversion. I think my calculations were right, I put 5 gallons of gas in and drove no more than 8 miles for sure before it was out:'(.

That link in my first post has a very detailed instructional for altering a curve for an inline 6 I just can't tell if applies to the 300 6 I have. here is the Instructional:

Re-curve the Duraspark II for Improved Mileage

If you have a DuraSpark II distributor, you also have smog-control spark advance curves inside. All of the DuraSpark units came this way, to reduce hydrocarbons. Unfortunately, it also reduces MPG. However... today's gasoline reduces the hydrocarbons for you, even more than the slow spark curve did. So, get a set of the Mr. Gasket #925D distributor springs and modify your distributor as follows:

First, remove the lighter of the 2 springs in the DII and replace it with one of the #925D springs. DO NOT replace both springs with the #925D springs (more on that in a moment). Next, there is a support arm that holds the larger spring, on it's non-slotted end. Bend this arm in toward the center of the distributor, just 3/32 of an inch.

This combination replicates the "police interceptor" distributor spark curve for the 200 I-6, according to a local "guru" who helped build these for Ford in the early 1980s. It causes earlier spark advance up to 1200 RPM, which then remains steady until 1800 RPM, when the secondary spring starts its advance. This "plateau" of early advance, limited by the 3/32" inward adjustment of the heavier spring, provides more torque at around-town speeds. This improves your MPG because you don't have to open the throttle as far to get the same speeds you were running before. You'll also notice better off-the-line pep and cold-running performance. Mine also starts a little better when hot, and the plugs stay cleaner. My in-town MPG rose from 16.5 average to 18.1 average over 2 tanks of gas, winter driving to and from work. I haven't tested the highway MPG yet, but I don't think it will improve from the 23+ I've been getting. I'll re-post if it does.

If you make the mistake of replacing BOTH springs in your DII with the #925D springs, you will get a SLOWER spark curve unless you extensively modify one of them to provide a "slot", like the heavier spring already has. But I found, even after that exercise, that the engine "hit the wall" at about 2200 RPM and would not accelerate well up hills. Adding in the heavier spring, but delaying its effect until 2000 RPM, did the trick: now it loves to rev, even on regular gas (my compression is about 9.4:1). The maximum advance is reached at 2600 RPM on my engine with this mod: before, the max advance was at 3200 RPM.

Written by FordSix member: Mark P.

All DSII distributors are built the same, except for the number of poles.
6 or 8

"police interceptor" and 200 I-6 in the same sentence ???
Come on now!

Do what you want, but a truck is heavy and needs a pretty slow curve IMO.

And there is NO WAY your truck engine is close to 9.4:1
It's lucky if it is 8:1

More important is total advance and what rpm's it comes in at.
You will notice two slots in the baseplate. (XXL)

Double this number and you will know how much centrifugal advance the slot will allow.
Springs just determine how fast the engine has to be spinning in order for it to reach that point.

I usually go with one heavy and one light, but this depends on the power to weight ratio of the vehicle.
Too much -OR- too soon and the knocking is going to kill your engine.

Check the Crane instructions.

That's not a reliable way to test your mileage, so I would not worry about that for now.

Sorry, that might have been confusing, That big long deal was the instructional. I am just starting to learn about this stuff and make no claims on my truck except that it is not optimized yet. Thank you everybody for your input.