Ignition system decisions...
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From: Muskegon, MI (home)
Ignition system decisions...
Hey guys, I am well underway on my frame off resto/mod of my 84 F150 4x4. The frame has been sandblasted, primed, and painted. All new brake and fuel lines have been run, 6" of suspension lift installed, rear disc brake conversion complete, engine and trans freshened up, all chassis, axle, and suspension components have been thoroughly cleaned and painted, and now the cab has been set back on the frame. Yep she's startin to look like a truck again. Now I am going through the wiring harness making needed repairs and uncobbling messes made by the previous owner. This truck was equipped with the TFI ignition system from the factory. I am trying to decide if I should leave the TFI, convert to the DS2 set up, or go HEI. Now is the time to do it, the entire cab is gutted... dash and all. I would like some tips and opinions from you fellers. What should I do: TFI, DS2, or HEI? Thanx in advance!
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TFI good enough
The TFI ignition is a pretty tough system. Its good for more R's than HEI; and less expensive than DS2. There is not much better than what you already have wiring for...
Last edited by mary-kate; Mar 25, 2008 at 11:25 PM. Reason: Clarity
Hotshot
Joined: Oct 2002
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From: The Big, Oregon
If you are going to use that *******ized electronic carb, then go with TFI.
If you are using a real carburetor, then go with DSII, you can't use TFI.
I have a Performance Distributors HEI distributor on the 300-6 in my truck, and unless the engine is really built the system really isn't worth the price difference from DSII.
In my 84 F250, the engine needed that much spark to get lit off, and would still occasionally drop a cylinder on WOT acceleration, but that thing was pushing way too much compression.
It's only on my 69's 300-6 because I had it and needed something better than points.
If you are using a real carburetor, then go with DSII, you can't use TFI.
I have a Performance Distributors HEI distributor on the 300-6 in my truck, and unless the engine is really built the system really isn't worth the price difference from DSII.
In my 84 F250, the engine needed that much spark to get lit off, and would still occasionally drop a cylinder on WOT acceleration, but that thing was pushing way too much compression.
It's only on my 69's 300-6 because I had it and needed something better than points.
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From: Nashville
Most aftermarket ignition boxes will adapt to work with whatever stock ignition system you have, and $$ spent there will net you better results than changing stock system "A" for stock system "B". I added a Mallory hyfire 6 [about $100] plus a new MSD coil to my stock DS2 and it made a world of difference. Though in perfect working order the DS2 just didn't have enough spark to properly ignite the mix after I added a new intake and carb.
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From: Muskegon, MI (home)
Sorry I guess I should have been a little more specific on my engine set up. It's punched .040 over, mild RV type cam, stock crank, rods, and pistons, Offy DP intake, Hedman header, and an Edelbrock 500 cfm 4bbl. This motor has seen it's fair share of WOT, especially running up in the sand dunes. It actually did run and ran very nicely with the TFI system on it, but I didn't have any of the extra wiring hooked up in the truck. I want to eliminate all the excess clutter in the engine compartment by deleting all the unused wiring. If I were to go with the DS2 set up and warm it up with an MSD box and coil, what other wiring would I need to obtain from the junkyard to get everything hooked up properly? I was pricing the MSD boxes and coils, I am almost wondering if the HEI set up would be easier and less expensive than trying to coordinate all the components of the DS2.
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Sorry to stop the conversation with a dumb question but i don't know what a HEI or TFI system is. Are they similar to the DUI system?
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Hotshot
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From: The Big, Oregon
The DUI is a reworked GM HEI distributor. You can see one in my gallery. HEI stands for High Energy Ignition, and generally uses a cap-mounted coil.
TFI stands for Thick Film Integrated. It's a computer controlled system that still uses a distributor, but there is no mechanical or vacuum advance. That is all handled by the computer.
TFI stands for Thick Film Integrated. It's a computer controlled system that still uses a distributor, but there is no mechanical or vacuum advance. That is all handled by the computer.
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Originally Posted by scrapyardking
I like points myself, nice and simple.
I always thought HEI stood for Hall Effect Ignition but I guess I was wrong. Hall Effect is what's behind breakerless ignition, Duraspark or HEI. My Chevy friends are always giving me garbage that HEI is so much reliable than Duraspark but it's the same thing. Same technology. There is NO difference in how the technology works (Note I did not say anything about performance differences between the two, I don't have that data). You've got a magnetic armature that turns and when a vein lines up with the Hall effect sensor (the pickup) you get a signal sent to the ignition module which uses that to open-circuit the coil ground which fires the plugs. The only thing HEI really has going for it is that everything is located on the distributor cap itself so there is less stuff running around. But those crazy Chevy people have their distributors all the way in the back of the motor for no reason so what does it matter.
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I've heard that if you run a DUI or HEI, i guess, that you don't have to worry about timing from the distributor. That the electronic module takes care of it? I don't see how this is possible, since you may need to advance or retard the timing for other reasons.
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Don't think that is correct as the early HEI and Duraspark systems had vacuum advances on the distributor. Once they came to throttle body the computors took over the advance function.
There were some problems with Duraspark boxes and the distributor module in the HEI, other then that they just worked. If point systems were installed properly(cam not over lubricated, and properly aligned, spring tension correct and the driver didn't leave the key on with the engine off) could be just as reliable at engine speed under 5000 rpm. Above that you might run in to some point bounce issues. I used to like to run a distributor tester up to about 3000 RPM (6000 engine) and see the degree wheel light pointers at twice as many spots as the distributor had lobes. You knew they were bouncing. kotzy
There were some problems with Duraspark boxes and the distributor module in the HEI, other then that they just worked. If point systems were installed properly(cam not over lubricated, and properly aligned, spring tension correct and the driver didn't leave the key on with the engine off) could be just as reliable at engine speed under 5000 rpm. Above that you might run in to some point bounce issues. I used to like to run a distributor tester up to about 3000 RPM (6000 engine) and see the degree wheel light pointers at twice as many spots as the distributor had lobes. You knew they were bouncing. kotzy
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Originally Posted by Duke78
I've heard that if you run a DUI or HEI, i guess, that you don't have to worry about timing from the distributor. That the electronic module takes care of it? I don't see how this is possible, since you may need to advance or retard the timing for other reasons.
What you probably heard was the fact that we custom curve our DUI distributors on a machine, so that you don't have to worry about going through trial and error trying to achieve the right advance curve.
As far as junkyard Durasparks are concerned, beware of their worn out upper bushing-they only have one. We utilize a full length oil impreganted bronze bushing in our Durasparks. This improves timing accuracy and it will be more durable for you. Junkyard Durasparks also can have worn out advance mechanisms.
http://www.performancedistributors.c...stributors.htm
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From: Muskegon, MI (home)
I am starting to lean more towards going with the HEI conversion due to the simplicity and clutter free installation. I was at a few junkyards today looking at the Duraspark wiring harnesses. From what I can see I will have to change out the entire underdash wiring harness to complete the swap. Is this correct or am I seeing things? Exactly how far into the main harness do I need to go, in order to switch to the Duraspark system?
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From: The Big, Oregon
Not at all. Use the original coil power wire to switch a relay, take the power for that straight off the battery, on branch to the box, the other to the positive side of the coil. Connect the distributor and spark box, orange to orange, purple to purple, black to black, green to the negative side of the coil, add an extra ground to the frame of the truck, and you're done. You can use just the red lead to give the box power, if you use the relay instead of resistor wire.
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