Blue tab ignition module and TFI coil..

[DynoDan]

I have been running this setup for years 69 302 but recently I have needed to replace the control module 2 times in the last 1500 miles,
Has something changed or is the quality of these boxes gone away?

Setup is using a 1977 version , blue tab module with a TFI coil (no ballast resistor) I have direct 12 volts going to the control unit .

Am considering converting to the GM unit, has anyone had good luck with that setup?

 

[DirtDonk]

Back to the top for you Dan.
I don’t have a specific answer for you, but yes parts have turned to crap in recent years.
Unfortunately it’s not limited to just recent years and a lot of cheaper Ford modules have been crap for close to 40 years.
Sometimes you get lucky, sometimes you don’t.

Lots of people have had good luck converting to the GM module and even used them inside the Ford housing.
Or were you speaking of going to the complete GM HEI style distributor?

 

[bmc69]

I've only bought NOS Motorcraft or Standard Blue Streak electrical components for the past couple decades. The crap they sell in a typical auto parts store is junk. I look up the part number and start searching on eBay..

 

[Broncobowsher]

The TFI coil is a good one. Pretty wicked hot spark. It might just be too much for the module.
Have you done a resistance measurement and compared to what is acceptable to a Duraspark? Even so it might still be too much with the ballast resistor delete you have done. The module is expecting the resistance of the ballast and what is internal to the coil.

I have done a TFI swap on my boat. Module and coil triggered off points. While testing it I was cycling the rotor (winding up the centrifugal advance and releasing) to open and close the points. Lovely spark. But I could watch the amp meter on the dash taking a healthy twitch each time as well. That TFI coil pulls a lot of amps. In TFI controlled conditions the dwell at idle is insanely low. Just a degree or two. Almost can't measure it. But the Duraspark is old school, weak little can coil that is pretty much 50% duty cycle. That is what the module is trying to do. I like the TFI coil, not sure about the Duraspark controlling it.

 

[DynoDan]

Back to the top for you Dan.
I don’t have a specific answer for you, but yes parts have turned to crap in recent years.
Unfortunately it’s not limited to just recent years and a lot of cheaper Ford modules have been crap for close to 40 years.
Sometimes you get lucky, sometimes you don’t.

Lots of people have had good luck converting to the GM module and even used them inside the Ford housing.
Or were you speaking of going to the complete GM HEI style distributor?

I think I will try a GM module. I have cleaned out a ford module and will use it as a heat sink. as you referenced

 

[DynoDan]

Oh, and have these failures occurred since going to the TFI coil by any chance?

Yes but they have occurred with the standard can coil as well. I went to the TFI 8 years ago with no problems

 

[DynoDan]

The TFI coil is a good one. Pretty wicked hot spark. It might just be too much for the module.
Have you done a resistance measurement and compared to what is acceptable to a Duraspark? Even so it might still be too much with the ballast resistor delete you have done. The module is expecting the resistance of the ballast and what is internal to the coil.

I have done a TFI swap on my boat. Module and coil triggered off points. While testing it I was cycling the rotor (winding up the centrifugal advance and releasing) to open and close the points. Lovely spark. But I could watch the amp meter on the dash taking a healthy twitch each time as well. That TFI coil pulls a lot of amps. In TFI controlled conditions the dwell at idle is insanely low. Just a degree or two. Almost can't measure it. But the Duraspark is old school, weak little can coil that is pretty much 50% duty cycle. That is what the module is trying to do. I like the TFI coil, not sure about the Duraspark controlling it.

I was under the impression that the TFI coil does nor want a ballast resistor.? What resistance measurement is acceptable to a Duraspark? Open to all ideas at this point!

 

[DirtDonk]

Well it’s probably true that the TFI style does not normally use a ballast resistor. But it’s also true that they were never to my knowledge used with a Duraspark external module.
TFI coils only came around with the advent of the TFI module and full computer controls.
No more need for a resistor…
TFI modules were mounted to the distributor, or when that proved to be problematic (due to heat oddly enough) mounted remotely in a heat sink.

But don’t think that was just a Ford issue. Early GM HEI setups also suffered from HREDS (heat related early death syndrome) and it becomes critically important to use the thermal transfer compound/paste that usually comes with a new module.
Don’t forget to use it even when using a Ford housing to dissipate heat.