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Folks, my 1990 Frankentruck has given a few good years of 20 mpg or better after it was resurrected a few years ago from Bubba in Mississippi who deleted nearly the entirety of factory efi parts for use with most of a JC Whitney chrome/speed part catalog.
I had spent months at local JYs to procure enough to complete the OE engine bay. And although a tick lean especially in winter, a rock solid reliable performer.
The day has come to morph the engine into an even more archaic form, with better intrinsic roadside repairability and high reliability. It is a manual trans so I have zero concerns of problems with other vehicle systems. I just completed a similar conversion on a 2001 Explorer 5.0 with some hurdles for technology retreat but fully successful.
The project is this- nobody has a solution for the 1989-91 dual plug head making carburetor easy. Solution is swap heads and regress. I want the DP late model head. There is no aftermarket intake avail not adaptors. There is not room for a distributor under the manifold as well.
I have a solution and it need not have any computer ignition control (albeit optional). It turns the 1990 platform into a carbd, distributed, mech and vac advanced vehicle, like its 1984 older sibling and the Ford Courier, while retaining the OE DP 90 head and nobody pulls the crank pulley either!!
As it turns out the lower intake manifold is ripe for adaptation. It is a dual two runner, equal length unit.
Intake mods: thread/tap all unused ports (injector, etc).
Cut off the ignition module heat sink block. Create a 4150 sized adaptor having the secondary half uncut. This produces a primary two barrel window. Fab a thin wall plenum/port location adaptor from 4150 base plate with a V partition to isolate the primary throats. Install a 600 cfm Edelbrock 1400 series NON AVS2 carb with secondary jets replaced with plugs, and linkage removed. This neuters the $50 donor carb into a two barrel, extremely easy “proper” cfm rated device with Jet and rod range appropriate, two corner idle. It’s a Weber 40 IDF with metering rods for $50 and bowls that will support any HP.
The ignition becomes interesting. I have in hand a NOS 77-82 Courier electronic mag pickup distributor. The distributor is well known to be too tall, any of them are too tall, to live under the manifold. That is——- still wearing a cap, rotor and spark plug wires.
The distributor body will fit, bare.
I will machine off some shaft height to allow the body to be as short as possible. I will lathe turn an aluminum trigger wheel with appropriate arbor to mount in place of the rotor. The wheel will be spindexed on the mill with 4x 1/8” neodymium magnets giving a resolution of 7.5 crank degrees full width and roughly half of that when triggering, spaced 90 degrees.
At two opposing magnets, the underside of the wheel will be milled receive a coil shaped thin magnet of 3/8 inch diameter.
This will give a “two” magnet pole at 180 offset and a “one” magnet pole for the other polar phase. This becomes the discrimination trigger or cylinder ID (CID) signal.
A pair of Littlefuse 55100 hall sensors will be arranged in 90 degree opposition, in an L shape pattern and molded into an epoxy/aliminum sheet form. A module that is NON critically aligned will be created that is user replaceable. This is the pickup device for the trigger wheel.
Interesting: by mounting both sensors/module on the existing gutted Ford/Mitsubishi/Mazda reluctor advance plate, the mechanical and vacuum advance systems operate as OE designed.
In essence, a distributor body based crank trigger with cam sensor is built with high precision, and is timed by hand as is typical with a dizzy. A cap will be machined from plastic that is low profile and flat topped to keep dirt out of the dizzy.
A circuit formed with an XOR and a NAND gate, both CMOS devices, will be fabricated, to interpret the trigger signals and route a current sink to a pair of HEI4 ignition modules. Each CMOS gate has quad devices so only one of each gate chip’s is required for both ignition banks.
The cast aluminum project box has a heat sink side and HEI will be mounted to this. A harness will be made with Deutsch connectors for ease of install and service. Will look a bit like a Duraspark box.
HEI handles dwell manipulation.
This low sophistication ignition box is field serviceable. HEI are roadside repairable. Likelihood of gate failure in 50 years of continuous service is about 1:1,000,000
This box then feeds coil triggers to the stock OE quad tower exhaust side coil. Yes it is a wasted spark system. Uses existing connectors from EFI system removal.
Basis of operation:
Large diameter magnet and associated trigger offers a trigger window of large duration. There are two and these magnets identify a pair of wasted spark cylinders. When the large mags are rising edge triggered far in advance of the spark event, the CMOS will be primed for the second precision event, the precise and narrow pulse from the small magnet and pickup. CMOS routes a pulse to the appropriate HEI. In the event NO BIG MAG is present and the small mag triggers, CMOS routes the pulse to opposite HEI. Dwell for the pulse from mag/trig/cmos is approx 1ms at idle speeds and much smaller at rpm.
This allows HEI full control from 5ms to 30ms dwell with a very short dwell trigger, Ala a reluctor wheel event in a real HEI.
Ignition is a low voltage wasted spark driver. CMOS operation allows for 12v logic level operation and seamless integration into auto electrical.
Back to carb- why a four barrel??? Edelbrock pre-AVS2 carbs are almost free. They are easier to tune than a Motorcraft or Autolite or even a Weber 32/36. Physically large, half of the device goes to sleep and never wakes. I have read many stories of drag racers dropping the secondaries in certain conditions to make runs. The secondary circuit is simple. Throttle blades, Venturi, jets in bowl. Plug the jets, disco the linkage and the primary is now autonomous.
The front crank seal is never violated. Radiator not pulled.
If someone decided they wanted a squirt or other ignition control computer- The trigger wheel gets an additional 12 small magnets evenly spindedexed into the edge of the wheel. The large mag is replaced with a small mag at both locations. This gives sufficient resolution for crank events as a gear down trigger mimicking a 720 degree cycle. The wheel would be a 16-2. Depending on needs, it is easy to go to 24-2 on trigger count. 24 teeth with 2 resets.
I have procured a donor manifold to be the fixture off-car during fabrication. Sensors, magnets, distributor in hand. Gates, HEIs and breadboard in hand. Gates simulated and scoped. Preparing to fab wheel and introduce the dizzy to it for real spin tests in the lathe as varying speeds.
No the system is not as accurate for timing as a real 36-1 crank trigger or similar. But it is far more accurate than the Point based dizzy it is mimicking, vastly easier to install than a crank trigger and for a bone stock 100hp beater truck engine- bullet proof, reliable and field serviceable.
The balance of conversion(efi subsystems) I’ll leave up to the imagination.
I will update with progress. A kit may come from this. Necessity is the mother of invention. I have needs.
I had spent months at local JYs to procure enough to complete the OE engine bay. And although a tick lean especially in winter, a rock solid reliable performer.
The day has come to morph the engine into an even more archaic form, with better intrinsic roadside repairability and high reliability. It is a manual trans so I have zero concerns of problems with other vehicle systems. I just completed a similar conversion on a 2001 Explorer 5.0 with some hurdles for technology retreat but fully successful.
The project is this- nobody has a solution for the 1989-91 dual plug head making carburetor easy. Solution is swap heads and regress. I want the DP late model head. There is no aftermarket intake avail not adaptors. There is not room for a distributor under the manifold as well.
I have a solution and it need not have any computer ignition control (albeit optional). It turns the 1990 platform into a carbd, distributed, mech and vac advanced vehicle, like its 1984 older sibling and the Ford Courier, while retaining the OE DP 90 head and nobody pulls the crank pulley either!!
As it turns out the lower intake manifold is ripe for adaptation. It is a dual two runner, equal length unit.
Intake mods: thread/tap all unused ports (injector, etc).
Cut off the ignition module heat sink block. Create a 4150 sized adaptor having the secondary half uncut. This produces a primary two barrel window. Fab a thin wall plenum/port location adaptor from 4150 base plate with a V partition to isolate the primary throats. Install a 600 cfm Edelbrock 1400 series NON AVS2 carb with secondary jets replaced with plugs, and linkage removed. This neuters the $50 donor carb into a two barrel, extremely easy “proper” cfm rated device with Jet and rod range appropriate, two corner idle. It’s a Weber 40 IDF with metering rods for $50 and bowls that will support any HP.
The ignition becomes interesting. I have in hand a NOS 77-82 Courier electronic mag pickup distributor. The distributor is well known to be too tall, any of them are too tall, to live under the manifold. That is——- still wearing a cap, rotor and spark plug wires.
The distributor body will fit, bare.
I will machine off some shaft height to allow the body to be as short as possible. I will lathe turn an aluminum trigger wheel with appropriate arbor to mount in place of the rotor. The wheel will be spindexed on the mill with 4x 1/8” neodymium magnets giving a resolution of 7.5 crank degrees full width and roughly half of that when triggering, spaced 90 degrees.
At two opposing magnets, the underside of the wheel will be milled receive a coil shaped thin magnet of 3/8 inch diameter.
This will give a “two” magnet pole at 180 offset and a “one” magnet pole for the other polar phase. This becomes the discrimination trigger or cylinder ID (CID) signal.
A pair of Littlefuse 55100 hall sensors will be arranged in 90 degree opposition, in an L shape pattern and molded into an epoxy/aliminum sheet form. A module that is NON critically aligned will be created that is user replaceable. This is the pickup device for the trigger wheel.
Interesting: by mounting both sensors/module on the existing gutted Ford/Mitsubishi/Mazda reluctor advance plate, the mechanical and vacuum advance systems operate as OE designed.
In essence, a distributor body based crank trigger with cam sensor is built with high precision, and is timed by hand as is typical with a dizzy. A cap will be machined from plastic that is low profile and flat topped to keep dirt out of the dizzy.
A circuit formed with an XOR and a NAND gate, both CMOS devices, will be fabricated, to interpret the trigger signals and route a current sink to a pair of HEI4 ignition modules. Each CMOS gate has quad devices so only one of each gate chip’s is required for both ignition banks.
The cast aluminum project box has a heat sink side and HEI will be mounted to this. A harness will be made with Deutsch connectors for ease of install and service. Will look a bit like a Duraspark box.
HEI handles dwell manipulation.
This low sophistication ignition box is field serviceable. HEI are roadside repairable. Likelihood of gate failure in 50 years of continuous service is about 1:1,000,000
This box then feeds coil triggers to the stock OE quad tower exhaust side coil. Yes it is a wasted spark system. Uses existing connectors from EFI system removal.
Basis of operation:
Large diameter magnet and associated trigger offers a trigger window of large duration. There are two and these magnets identify a pair of wasted spark cylinders. When the large mags are rising edge triggered far in advance of the spark event, the CMOS will be primed for the second precision event, the precise and narrow pulse from the small magnet and pickup. CMOS routes a pulse to the appropriate HEI. In the event NO BIG MAG is present and the small mag triggers, CMOS routes the pulse to opposite HEI. Dwell for the pulse from mag/trig/cmos is approx 1ms at idle speeds and much smaller at rpm.
This allows HEI full control from 5ms to 30ms dwell with a very short dwell trigger, Ala a reluctor wheel event in a real HEI.
Ignition is a low voltage wasted spark driver. CMOS operation allows for 12v logic level operation and seamless integration into auto electrical.
Back to carb- why a four barrel??? Edelbrock pre-AVS2 carbs are almost free. They are easier to tune than a Motorcraft or Autolite or even a Weber 32/36. Physically large, half of the device goes to sleep and never wakes. I have read many stories of drag racers dropping the secondaries in certain conditions to make runs. The secondary circuit is simple. Throttle blades, Venturi, jets in bowl. Plug the jets, disco the linkage and the primary is now autonomous.
The front crank seal is never violated. Radiator not pulled.
If someone decided they wanted a squirt or other ignition control computer- The trigger wheel gets an additional 12 small magnets evenly spindedexed into the edge of the wheel. The large mag is replaced with a small mag at both locations. This gives sufficient resolution for crank events as a gear down trigger mimicking a 720 degree cycle. The wheel would be a 16-2. Depending on needs, it is easy to go to 24-2 on trigger count. 24 teeth with 2 resets.
I have procured a donor manifold to be the fixture off-car during fabrication. Sensors, magnets, distributor in hand. Gates, HEIs and breadboard in hand. Gates simulated and scoped. Preparing to fab wheel and introduce the dizzy to it for real spin tests in the lathe as varying speeds.
No the system is not as accurate for timing as a real 36-1 crank trigger or similar. But it is far more accurate than the Point based dizzy it is mimicking, vastly easier to install than a crank trigger and for a bone stock 100hp beater truck engine- bullet proof, reliable and field serviceable.
The balance of conversion(efi subsystems) I’ll leave up to the imagination.
I will update with progress. A kit may come from this. Necessity is the mother of invention. I have needs.
