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HEI Distributor replacement

  
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HEI Distributor replacement

 
1robert1 1robert1
New User | Posts: 7 | Joined: 07/12
Posted: 02/10/13
11:10 AM

Hello: I have two questions regarding Distributor replacement.
I was given a GM HEI Distributor from a neighbor who is a retired parts desk man for a local Chevy delearship. He says the unit is like new
My 74 C20 has a points distributor.
I have looked in the service manual but do not see anything specific on testing the unit to make sure it works. Any suggestions on this , other than just droping it in and trying it out?
Also once installed, is there anything special needed:certain wires, plugs, etc? If anyone can suggest an one line source for research, it would be helpful. When I access the net I usually only get Ads to sell parts?
Any suggestions are appriciated.  

waynep71222 waynep71222
User | Posts: 221 | Joined: 05/12
Posted: 02/10/13
05:11 PM

i can help you thru Bench  testing the HEI...

does it have a cap and rotor on it??????

do you have a set of jumper cables...  and some kind of wire to plug into the BAT terminal on the side of the cap that you can hook to a positive battery...

please follow this order so you don't get shocked...  

completely assembled HEI minus the spark plug wires..    

take a 12 volt car battery..     hook both clamps on one end to the NEGATIVE post...

find a flat piece of metal..  big enough to  allow you to turn the HEI upside down on and have all 8 wire terminals near the metal..

one clamp goes on the  housing .. usually down where it sticks into the engine.. NOT ON THE SHAFT that spins..

the other clamp goes on the piece of metal you are going to turn the HEI upside down on.. so the sparks will JUMP TO THIS GROUNDED steel or aluminum plate... not to you...

with the HEI upside down... and  positioned on the grounded plate..    hook up the HEI bat terminal to the positive on the same battery...     now.. as long as you don't pull the hei away from the steel plate.. you can spin the shaft and create sparks to see if the HEI actually works..


ask if you have problems..   parts are available at almost any parts store...

two things...  when you convert a 74 to HEI..   you will probably want to convert /replace the ignition switch on the column..  if it has not been replaced in the last 3 decades..

i usually use the factory coil positive wiring to control a RELAY that is supplied with switching power from the terminal block on the firewall...  or i replace the resistance fiber insulated wire from the bulk head connector with a donor wire from an HEI equipped GM car or truck starting in 75 though around 80 or 81.. should have the proper bulk head connector terminal to allow you to extract the terminal and install the thicker wire ..


i have a few more tips for installing hel in that model as i have done a bunch of them..  

1robert1 1robert1
New User | Posts: 7 | Joined: 07/12
Posted: 02/11/13
07:34 PM

Waynep71222;
I want to thank you for a remarkably detailed outline for bench testing the HEI distributor. I can honestly say I have never done such a test but am anxious to give it a go. I have a weeks vacation in March. Was planning to play with the truck then so this will be added to the mix.

I have some Brass Shim Stock that should work: also battery, jumper cables,  various guage wires and aligator clips. Should be able to determine if the unit works
Not following completly your suggestion for replacement of the insulated wire on the firewall with a donor wire from an 75/newer application. But before I begin to ask questions ( I'll probably have one or two) I want to examine what I have.  It will Help me to look at what I have and compare to your advise.
Pretty sure the ignition switch has quite a few years on it.
This is a project, not a daily driver, so it will probably be the weekend before I can have some free time with it.
I appriciate your advice.  

waynep71222 waynep71222
User | Posts: 221 | Joined: 05/12
Posted: 02/11/13
10:40 PM

for a base... one could use an air cleaner lid...  just as long as its grounded... so the sparks can jump to it.. and go back to ground in the distributer housing... to make a complete high voltage circuit..



the wire from the bulk head connector next to the power brake booster is a fiberglass coated 18 gauge resistance wire...

most HEI power wires are 12 gauge with a plastic insulation...

in point type ignition systems...    when you turn the key to the RUN position.. the power comes from the ignition switch IGN1 terminal to several items and the bulk head connector as a PINK wire usually...   from the bulk head connector on the engine compartment side it becomes a 18 gauge resistance wire to reduce voltage to the ignition coil and prevent point burn out...

during cranking on a chevy or GMC..  the voltage to the positive side of the ignition coil is supplied by the R terminal on the starter solenoid... this boosts the voltage up to cranking voltage levels usually around 12.2 or 12.4 volts. if the battery is fully charged.. verses 9.6 to 10 volts during the RUN...

the issue is the HEI to be fully effective needs as much current as possible .. having TINY wires supplying it just limits the HEIs ability to fully saturate the primary coil winding ..

reduced voltage also increases current needs...   this can effect the life span of the ignition module..

thats why i posted several different ways...   swap the ignition switch to the replacement..  i have a replacement for dash mounted switches also...  

swap on a wire from almost any mid to late 70s GM with HEI.. if you take a 3/8 as i recall socket and unscrew the middle nut in the bulk head connector .. you can take the connector off.. squeeze the terminals and extract the wires you need...  not always easy... not always available depending on junk yards in your area..

i was just given a nice 8 or 12MP camera.. i will take some pictures this week.. post them..


you may also want to hot rod your starting circuit..  with a 70 dodge dart starter relay..

Starter Load Dropping Relay  

waynep71222 waynep71222
User | Posts: 221 | Joined: 05/12
Posted: 02/11/13
10:46 PM

one last thing... spark plug wires...  

are your manifolds all below the spark plugs... hopefully...

some sets have angled boots at the spark plugs..

some sets are all straight boots at the spark plugs

some are some of each...  

1robert1 1robert1
New User | Posts: 7 | Joined: 07/12
Posted: 04/03/13
08:08 PM

Waynep71222:
Finally had time to check out he HEI distributor. was quite a project but determined the HEI unit does work. Again thanks for your bench tech advice.
Understand the need to swap out for bigger guage wire to support voltage load for HEI. If I follow you: I can either swap out the entire starter switch from a Mid+ 70's; or up grade the guage wire from the balast resistor on the Firewall? Is that correct? what about the R wire from the starter? Plan a trip to the junk yard soon to see what they have. Plug wires: all striaght boot; manifold below heat shield equiped. was told by the old fellow who gave me the HEI I should up grade wires and plugs too for the HEI install.any advise on that. I appriciate your input Thanks  

waynep712222 waynep712222
User | Posts: 209 | Joined: 03/13
Posted: 04/04/13
07:49 AM

74 GMC PU Wiringdiagram Zpsf2f1be84

follow the wire that comes out of the left side of the coil on this diagram... it goes into cavity #4 on the diagram...   you can pick up a HEI power wire from almost any mid 70s gm car or truck in the junk yard..  at some point in the early 80s.. i think they changed the shape of the bulk head wiring terminals...

just replace  depin the connector.. install the new wire to the HEI...

you can also cut the resistor wire fairly short.. and crimp the new larger wire to it.. length is the resistance with the resistor wire .. so a few inches or less is not going to reduce voltage very much..

swapping to the replacement switch will fix the breaks contact while cranking..  straight and tilt use different ignition switches..

Tiltcolumnignitionswitch

this is a diagram i highlighted for the fusible links for a 77 to 80 chevy truck..

follow circuit 3... its not colored in this diagram...

77 80 Chevytruck Fusible Links

note that 3 also supplies power  to the wiper motor...  

waynep712222 waynep712222
User | Posts: 209 | Joined: 03/13
Posted: 04/04/13
07:54 AM

what happens to the BROWN wire to the R terminal on the starter solenoid...

test the NEW HEI power circuit with a circuit test light...

do you have power when the key is on.. and while cranking..  and back to the ON.. then you can just disconnect it...  tape it back to the harness or cut the terminal off... so it cannot short..

do you see on the 77 to 80 wiring diagram .. the terminal block shown above the wiper switch..

that is a good place to grab power from if you wanted to use a relay to power the HEI...  

1robert1 1robert1
New User | Posts: 7 | Joined: 07/12
Posted: 04/05/13
09:18 PM

Waynep712222:
This is great information: the diagrams, with the aid or your advice, are fairly easy to understand: Clearly you have done this swap out a few times as you had mentioned. Going to try and get to the junkyard tomorrow if I can make it before they close. With any luck will find what I need. Then the next free weekend I get it will be time to give it a go. Getting anxious to see if this thing will fly. Thanks again for your help and advice on this: much appriciated.
I'll let you know what develops.  

1robert1 1robert1
New User | Posts: 7 | Joined: 07/12
Posted: 05/28/13
08:06 PM

Waynep712222:
Got to the HEI distributor this weekend. Long and short of it is: 'got er done':  your advice was right on. Set her up on TDC and the unit dropped in too easy; thought something was wrong... even reconfigured the wiring without to much head scratching. After triple checking everything, gave her a go and she fired right up. Haven't gone any distance yet, only around a few blocks; seems fine. Sure idles smoother but that might be the new plugs and wires: who knows. In any case on to the next project. thanks again for the help on this.
1Robert1  

waynep712222 waynep712222
User | Posts: 209 | Joined: 03/13
Posted: 05/28/13
10:16 PM

great.... glad to have been able to help....