Davis Unified Ignition HEI installation for noobs

[HawkGunner]

After studying the wiring diagrams and all the info I had available, and reading through threads, and asking the pro's around here, I went ahead and installed the DUI HEI dizzy. I'm writing a thread for anyone like me looking for all the info in one place.

I decided that running it through an "ignition" relay was the safest option, e ven though my OE system would theoretically allow it to be run off the existing wiring (I don't have a Yazaki Resistor wire), doing so might overload the already taxed ignition switch, and the distributor might not get enough constant juice to operate properly.

I had to move the heater pipe below the distributor. This sucker is big and needed some room. I also needed to grind one of the studs that held the heater pipe down slightly, and a portion of the top "lip" on the lifter cover to make room to allow the new dizzy to turn. But a quick glance wouldn't show this, especially as both modified components are hidden by the distributor, and they aren't major modifications.

Since I had the dizzy out, I changed the lifter cover gasket, and insulated my fuel line as well to help prevent hot starting and vapor lock.

With the engine mechanically timed, the HEI installed and checked to see if it was bottoming out, I positioned the cap and used the post that was over the button as my No. 1, then followed the original firing sequence.

I left the OE ignition system in place in case I need to or want to switch back to the OE style dizzy. I have a new FJ60 non-USA one laying around with a Mel's electronic ignition kit installed.... just in case.

Will post more entries.

 

[HawkGunner]

I used the large BY wire from Ignitor plug to Terminal 86 on relay(the small BY bypass wire can be used as well). Ground terminal 85 to body or take it to the negative battery terminal (I opted for the battery, as it was close and is the most efficient ground). Connect a 12ga wire to Terminal 30 on relay then to a 15 amp fuse, then to battery + post. Last, connect Relay terminal 87 to the DUI with the supplied connector. When you turn on the key the relay will energize providing the DUI with a good solid +12V.

I used 12ga wire throughout.

All that's left to do now is waterproof the OE plug with the new connection.

 

[HawkGunner]

I attached the ground wire to the battery terminal with a spade lug and clamped it down. Then added a coat liquid electrical tape to help prevent corrosion and moisture.

 

[HawkGunner]

I bought both the in-line fuse and the four post 30 amp generic relay from O'reillys for just a few dollars. The relay wasn't waterproof, so I used liquid electrical tape on the open seams on the bottom. It's waterproof now!

All connections were shrink-tubed after connecting to help resist water and to aid in durability.

The relay was bolted down to where the front "quarter panel" bolts down on the fender.

 

[HawkGunner]

This is the plug that goes to the OE ignitor/coil combo. Check your large BY wire to see if it's got the Yazaki resistor. Turn the key in the on position, and measure between the battery and the BY wire terminal for source voltage. If you have a full battery and only show 9 or 10 volts, you have the Yazaki resistor wire, as opposed to a ballast in the ignitor. Theoretically (and some people do), if you don't have a resisted wire, you can run the dizzy straight from this wire. I just don't think it's a good idea.

The ignition switch is already operating at a high capacity, and this distributor needs a constant 12+ volts to run properly. The best place to get that is straight off the battery.

 

[HawkGunner]

All connections were crimped, soldered, and coated with liquid electrical tape. Then shrink-tubed for water resistance and durability. Continuity was checked after all stages of assembly.

I also prefer as clean a look as I can get. Open solders and sealant look like doodoo IMO

 

[HawkGunner]

Not really related to the distributor, but since it wasn't obstructed with the alternator bracket, I insulated the fuel line with foam insulation tube and ducting insulation aluminum tape from the air conditioning section at Home Depot. It doesn't look that great, which annoys me. But, vapor lock and hot starts annoy me more. Hopefully it helps out this summer!

Time will tell.

 

[HawkGunner]

Finally, while I assembled all of this from scratch and didn't have time to wait, @Coolerman makes a waterproof relay kit for $24.

If you aren't a do-it-yourselfer, search him out.

 

[HawkGunner]

Additional info:

I gapped the plugs to .050. The manufacturer claims the dizzy can handle up to .055.

My initial timing is set at approximately 8° to 12° advanced... I don't have an adjustable timing light, so i eyeballed it (the timing BB is slightly forward of the needle). This was set without the vacuum advance connected, as per the manufacturers directions.

I'll probably adjust the timing slightly in the next few days. For now, I've driven it around the block at about 30mph. Highway speeds will likely prompt some tuning.

 

[chubot]

Where did you order your dizzy? I have a Trollhole dizzy and I haven’t had any luck with the little ignition modules. I would install a pertronix in my original dizzy but the old vacuum advance doesn’t move as freely as it should and I’ve already rebuilt it once.

 

[HawkGunner]

Where did you order your dizzy? I have a Trollhole dizzy and I haven’t had any luck with the little ignition modules. I would install a pertronix in my original dizzy but the old vacuum advance doesn’t move as freely as it should and I’ve already rebuilt it once.

I ordered it from Summit Racing, but I believe it shipped directly from the DUI factory.

I also ordered the wires from Summit too. Manufacturer says you have to use their wires. I needed new wires anyways and wasnt going to argue.

 

[leathamtj]

Hello! I was wondering if anyone knows what to do with the two vacuum lines that went on the old distributor cap since the hei does not use these. Thanks

 

[HawkGunner]

Hello! I was wondering if anyone knows what to do with the two vacuum lines that went on the old distributor cap since the hei does not use these. Thanks

The HEI distributor requires vacuum. So the vacuum line from the carb needs to be connected to the vacuum diaphragm on the distributor.

I dont know what kind of carb you have. But any unused vacuum ports need to be plugged.

 

[wngrog]

Get on Summit and get some black heat wrap. You gotta lose that shiny stuff. Engine area looks too good for that stuff.

 

[HawkGunner]

Get on Summit and get some black heat wrap. You gotta lose that shiny stuff. Engine area looks too good for that stuff.

I agree, but I need to remove my alternator and bracket to do it. It probably won't happen any time soon lol.

Thinking about doing a 3FE swap as soon as funds allow anyways, and rebuilding this 2F as a backup.

 

[wngrog]

I don’t think something is right in your carb if you are having the hot start issue like that though.

I’ve got 4 trucks with F and 2F Motors in the Deep South and ive never experienced that.

Thanks for the writup. Never knew about the Yazaki Resistor.

 

[HawkGunner]

I don’t think something is right in your carb if you are having the hot start issue like that though.

I’ve got 4 trucks with F and 2F Motors in the Deep South and ive never experienced that.

Thanks for the writup. Never knew about the Yazaki Resistor.

I wasn't experiencing a no-start hot start. But it was more difficult to start after I'd run down the interstate for an hour in 110 heat. I would shut it down at the gas station, gas up, grab a drink etc. And by the time it heat soaked for a few minutes, it would be difficult to start.

The insulation, as ugly as it is, has made a noticable difference. The truck fires up much more readily under the same conditions now.

 

[Solace in Solitude]

Great write up!!

To elaborate slightly:

My ‘78 had the big (8ga) pink Yazaki Resistor wire spliced into the 8ga BY wire. I disconnected the 8ga BY wire and taped it off.

I used the small BY wire to trigger a relay-86 and used 8ga red wire (because I had it available and because DUI requires full 12vdc... and I’ve gapped my plugs at .055”), from the battery+ To relay-31/50 and from relay-87 to DUI. Relay-85 goes to ground.

I’ve never experienced hot start issues with my DUI.

Regarding your hot start issue... potential slight differences between your setup and mine:

You described your initial timing at ~7-8*BTDC... where did your timing end up?

DUI recommends 12BTDC... 12BTDC works great for me.

12*BTDC is roughly with the BB at the top of the window.

What about spark plug gap?

DUI recommends .050-.055”... I run Denso W14EXR-U plugs, gapped at .055”... works great for me.

Hope that helps!

I hope you don’t mind me including the DUI literature in your thread:

Installation:

Troubleshooting:

 

[Solace in Solitude]

@leathamtj

What year 40?

If your DUI doesn’t have a vacuum advance module, you might want to exchange for the DUI with the vacuum advance.

Also, be sure it’s the Toyota DUI... the wrong (none-Toyota) gear will with damage your engine.

 

[HawkGunner]

@Solace in Solitude , no problem at all! I'm glad you included the literature too. I should have done that when I originally posted.

When I first installed it, I couldn't find many good answers on the subject, even though lots of people seemed to either have or want the DUI HEI. I hoped to put the minimum necessary info in one place, so I'm glad you added what you did.

I ended up with my timing at about 12°. I borrowed an adjustable timing from the shop and set it up.

As far as the hot-start issue, I can't say whether the insulation or the HEI dizzy fixed it. Either way, it fires up pretty good now. Well enough that I'm not worried about getting stranded somewhere.

Eventually I'm doing a 3FE swap, but for now I just need to get around to overhauling my transfer case and my 40 will be road-trip worthy! hahaha