My $25 stock appearing HEI conversion

[UKcuda]

Hey thanks Bullitt, I knew it had to be something simple.

I'm ging to try this:

http://www.camaros.net/techref/electrical/tachfilter/

I've got plenty of old radios and things lying around my workshop so I think I can find an appropriate resistor and capacitor without even going into town.

I think I wouldn't even need to remove it if I needed to swap back to standard ignition.

I'll let you know how it works.

[UKcuda]

OK, the filter didn't work but I've invented something else which does !!

By the way, the filter stopped the tach from working at all.

Thinking that the problem might be caused by the fact that the HEI has in effect a variable dwell, and the stock system has a fixed dwell, I wondered if the problem could be cured by losing half of the HEI signal.

So, I decided to try half wave rectifying the signal with a diode. 

Since all I could find was a tiny little diode off an old circuit board I put a 1k ohm resistor in series with it as a bit of protection for the poor little fella.

I have no idea if my theoretical reason for doing this was sound, but who cares - it works - the tach is now rock steady and appears to be reading correctly.

Let the good times roll.

[Bullitt-]

  Good Job UK! 

Googled "HEI tac diode" and came up with many hits.. Seems to be a common problem when using a MSD box as well .

[ragtopdodge]

Good job, but this setup is a bit cleaner looking:

http://www.designed2drive.com/

[Cooter]

Well now, this here thread has my attention...I'm liking the $25.oo for 50K volts...NICE Ukcuda, you got my vote.

[nqkjw]

Well now, this here thread has my attention...I'm liking the $25.oo for 50K volts...NICE Ukcuda, you got my vote.

Cooter - there's lots more info and wiring diagram in this thread

http://www.cuda-challenger.com/cc/index.php?topic=72835.0

[UKcuda]

Good job, but this setup is a bit cleaner looking:

http://www.designed2drive.com/

Not sure how that is "cleaner looking" when it involves bolting an external bracket and HEI to the outside of the distributor, as compared to mine where everything is hidden and 100% stock looking.

It also adds $40 to the project - I think the only thing "cleaner looking" will be your wallet 

[ragtopdodge]

Not sure how that is "cleaner looking" when it involves bolting an external bracket and HEI to the outside of the distributor, as compared to mine where everything is hidden and 100% stock looking.

It also adds $40 to the project - I think the only thing "cleaner looking" will be your wallet 

No external box.  I still don't understand why some people have pristine looking engine compartments, and then bolt on the darn orange box on the firewall when it didn't come like that from the factory (unless you have a 1972+ car).

[1970 RT Challenger 1970]

Interesting Conversion!

[UKcuda]

No external box.  I still don't understand why some people have pristine looking engine compartments, and then bolt on the darn orange box on the firewall when it didn't come like that from the factory (unless you have a 1972+ car).

I see what you mean.  You were thinking about pre-1972 cars and I have a 1972 car.  But if I had an earlier car I would not have mounted the HEI inside a Mopar ignition box "to keep it stock looking".  I partly did that so that all the wiring and connectors etc. stayed stock. 

If I had an earlier car I think I would have found somewhere else to hide the HEI, like even maybe on the other side of the firewall.  The wiring would then have been slightly different from stock, but that's inevitable when you change from a points distributor to an electronic one.

[ShelbyDogg]

Here is my HEI 8-Pin module conversion.  Used for my EFI computer controled timing.

Without the connector on the left plugged in, it works just like a regular Mopar ECU.

[Justins72]

Would this work? http://www.summitracing.com/parts/PNX-D2000/

IM liking the whole Idea and my car is just street driven so I wouldnt worry about high rpm's

[UKcuda]

Would this work? http://www.summitracing.com/parts/PNX-D2000/

IM liking the whole Idea and my car is just street driven so I wouldnt worry about high rpm's

Yes that will work.  It's just pertronix pretending they have done something original; they haven't, it's the same thing. 

Here's the one I used:  http://www.summitracing.com/parts/MAA-607/

It was a bit cheaper last year when I bought mine but it's still cheaper than the pertronix one and I think it's just as good.

If you want to go bargain basement then Rock Auto has some similar units for $17.  I tried one on my '72 Mustang and it seems just as good as the Mallory one I used on the 'cuda.  Both of them have been a big improvement over stock.

[Justins72]

Im going to be converting my challenger over to this and I read somewhere about using the modern ecore coil. What would be a good coil?

[UKcuda]

On my 'cuda I used the Accel coil that was already on there but when I did the same conversion on my '72 Mustang I bought an E-core listed for a '94 Mustang - I think it is an AC Delco part number F581

I have also seen Wells C839 coil or equivalent recommended. 

Almost any Ford TFI coil seems to be a good choice, and they are cheap as chips (I guess you would say "cheap as fries" but it doesn't sound the same)