Drift Castaway Posted March 7, 2022 Share Posted March 7, 2022 So funds are a little tight right now, and I had an idea born of sleep deprivation and caffeine and I wanted to get some advice from some of the mad scientists in this group. I've got an 84 with the 4.9 and TFI ignition system, I have a dura spark ii coil, a duraspark blue module, and a non feedback carb (which is currently installed on the vehicle resulting in absolute shite performance) My question is, is there any way to wire the dura spark module to the TFI distributor as a short-term way to get it out of limp mode until I can afford a new distributor? 100% fully understand that it is not a practical, easy, or long-term solution. I'm more curious just to see if it can be done as the distributor is only about 6 months old and I really don't have the funds to throw at a new distributor at the moment. And before I get asked "why did you buy the wrong distributor?" I'm not the one that replaced it LOL Link to comment Share on other sites More sharing options...
mat in tn Posted March 7, 2022 Share Posted March 7, 2022 I don't believe that you can "mix" the systems. Link to comment Share on other sites More sharing options...
StraightSix Posted March 7, 2022 Share Posted March 7, 2022 I don't believe that you can "mix" the systems. Yeah :( I may be mistaken, but I dont think the TFI dizzy has any provisions for mechanical advance and it certainly doesn't allow for vacuum advance. IF you got it to work I suspect it would only be good enough to get the thing around in the yard without having to push it. This is al because your timing would be static at whatever value you set for base timing. It probably wouldn't be drivable at all. I know you said buying a distributor was off the table right now, but you might be surprised how inexpensive a JY distributor could be. I dont know how junk yards are in your area but around here I assume that would be $30-50. you might even walk out with the module and coil from the same truck for the same price. this is by far the easiest and cheapest route to having a road worth engine again that I can see. edit - yep, I checked on the TFI dizzy sitting in my parts pile. no mechanical advance. come to think of it, Im pretty sure the limp mode on these things involves locking timing at base timing. This means that even if you did manage to get it all to work you would end up with the exact same thing you have now, timing locked at base. Sorry :( here is one on ebay for $40. you dont even have to go to the pick N pull. https://www.ebay.com/itm/281718597323?hash=item4197bca6cb:g:dowAAOSwpDdVeE5t Link to comment Share on other sites More sharing options...
Drift Castaway Posted March 7, 2022 Author Share Posted March 7, 2022 I really appreciate the input guys. Right now I'm running with the non feedback carb, have been for about 6 months now and gas prices locally just hiked up $0.65 overnight (now it's 4.70) and it's finally motivating me to start putting some thought into this LOL. Somebody on another forum said something about removing a locking pin and installing a vacuum advance on this distributor? That seemed like it's a little far out there, and it certainly not anything I've ever heard of, is that a thing you can do? That's a good idea on the junkyard, I just don't have one with a dii truck within about an hour of me so I'll have to see what I can't wrestle up. Link to comment Share on other sites More sharing options...
StraightSix Posted March 7, 2022 Share Posted March 7, 2022 I really appreciate the input guys. Right now I'm running with the non feedback carb, have been for about 6 months now and gas prices locally just hiked up $0.65 overnight (now it's 4.70) and it's finally motivating me to start putting some thought into this LOL. Somebody on another forum said something about removing a locking pin and installing a vacuum advance on this distributor? That seemed like it's a little far out there, and it certainly not anything I've ever heard of, is that a thing you can do? That's a good idea on the junkyard, I just don't have one with a dii truck within about an hour of me so I'll have to see what I can't wrestle up. I feel ya on gas prices :( mechanical advance and vacuum advance both serve their purpose. many vehicles with aftermarket distributors dont have a vacuum advance at all and our trucks drive just fine with the vacuum advance disconnected in many cases. Basically, when the throttle plates are partially closed the engine is less able to fill the cylinder with intake charge. this results in more exhaust gasses relative to intake gasses in the cylinder on the compression stroke. This mixture burns more slowly than a more pure intake charge would, so you need more timing advance to get the best out of that cycle. The vacuum advance accomplishes this by using vacuum from the manifold (which is higher when the throttle plates are more closed) to advance timing. you can run without vacuum advance. I did it for a few weeks because I had a faulty vac advance canister. I went from 16 MPG highway to 13 MGP highway, and lost a notable amount of mid throttle performance. but it will run and drive fine. unfortunately, the mechanical advance is really important, you just have to have it. As the engine runs at higher and higher rpm, there is less time for the combustion process to occur. the period of time required for the charge to combust does speed up slightly, but not nearly enough to keep up with the decrease in time available to burn. mechanical advance compensates for this by advancing ignition as the engine rpm increases. the faster the engine spins (up to a point) the more timing advance you get. the mechanical advance is the part you TFI distributor wont do, and its the part that you really have to have. I dont think you can make your TFI work any better with a ds2 box than it does right now, and I dont think there is anything you can do for $40 that will work as well as putting in a ds2 distributor. here is a link for a cool article about how spring/weight mechanical advance works, understanding base timing, mechanical advance and vacuum advance, etc. I think if you give this a read it will all make more sense. http://vb.foureyedpride.com/showthread.php?22229-The-Ultimate-Duraspark-Distributor-Timing-Guide Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 7, 2022 Share Posted March 7, 2022 I really appreciate the input guys. Right now I'm running with the non feedback carb, have been for about 6 months now and gas prices locally just hiked up $0.65 overnight (now it's 4.70) and it's finally motivating me to start putting some thought into this LOL. Somebody on another forum said something about removing a locking pin and installing a vacuum advance on this distributor? That seemed like it's a little far out there, and it certainly not anything I've ever heard of, is that a thing you can do? That's a good idea on the junkyard, I just don't have one with a dii truck within about an hour of me so I'll have to see what I can't wrestle up. The TFI distributor is all computer-controlled. It has no centrifugal nor vacuum advance. So even if you could pull a pin and add a vacuum advance, which I seriously doubt, you'd be wasting your time as there aren't any weights or advance mechanism for centrifugal. Basically, if you could do it you'd be right back where you are - with the computer having locked the timing to initial. You are in limp-home mode and until you put the complete feedback system back on to make the computer happy, or change out to a DS-II system you will have poor power and MPG. Link to comment Share on other sites More sharing options...
Drift Castaway Posted April 5, 2022 Author Share Posted April 5, 2022 The TFI distributor is all computer-controlled. It has no centrifugal nor vacuum advance. So even if you could pull a pin and add a vacuum advance, which I seriously doubt, you'd be wasting your time as there aren't any weights or advance mechanism for centrifugal. Basically, if you could do it you'd be right back where you are - with the computer having locked the timing to initial. You are in limp-home mode and until you put the complete feedback system back on to make the computer happy, or change out to a DS-II system you will have poor power and MPG. Awesome advice guys! Thanks for the answers! I've sourced a distributor, coil, and ignition module, but so far I've been unable to find a correct wiring harness so I bought a ballast resistor and I'm going to attempt to make one so wish me luck! Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 5, 2022 Share Posted April 5, 2022 Awesome advice guys! Thanks for the answers! I've sourced a distributor, coil, and ignition module, but so far I've been unable to find a correct wiring harness so I bought a ballast resistor and I'm going to attempt to make one so wish me luck! The difficult connector to find is the orange/purple/black one for the DSII distributor. AFAIK Painless has them made special for their wiring kits. Link to comment Share on other sites More sharing options...
Drift Castaway Posted April 12, 2022 Author Share Posted April 12, 2022 Just a follow up, I've completed the dii conversion on my truck! It made absolutely all the difference in the world! Ended up getting the painless wiring harness, a new job at O'Reilly's and the employee discount that entails made getting parts a heck of a lot easier. 😂😂😂 Thank you guys for weighing in Link to comment Share on other sites More sharing options...
Gary Lewis Posted April 12, 2022 Share Posted April 12, 2022 Just a follow up, I've completed the dii conversion on my truck! It made absolutely all the difference in the world! Ended up getting the painless wiring harness, a new job at O'Reilly's and the employee discount that entails made getting parts a heck of a lot easier. 😂😂😂 Thank you guys for weighing in Congratulations!!! Seems like you are making really good progress, both on the truck as well as the job. Link to comment Share on other sites More sharing options...
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