How to install an old HEI on '72 GMC Pickup

[slowboy]

I've seen a lot of post on what it takes to replace points distributor with an HEI [non computer controlled]. Things like needing to be calibrated for advanced curve and other things. I know how important it is to know these things, but is there anyone that can tell me 'how' to do these things?
A friend of mine gave me an old HEI distributor several years ago. As mentioned in another post, I'm one of those that thought that I could just drop an HEI in and receive all the advantages and results from this swap.
Since putting HEI in, my old 350's performance and gas mileage has suffered tremendously. I put new weights and springs on HEI, but didn't seem to help much if any at all. I don't recall if I replaced coil or not. It seems that I would have though when I replaced weights and springs. I was told to change springs to lighter ones to allow better advance, so I did. I put the 2 lightest springs in kit. This did not help either.
I put E3 plugs in hoping for improvement, but did not help. After reading previous post, I saw where y'all were running a plug gap ranging anywhere from .035-.050...and the initial timing ranging anywhere from 8deg btdc-18deg btdc. I bought new set of plugs and gapped then at .045, and set initial timing [after trying 8-10-12-14-16 and 18 btdc] at 16deg btdc where it seemed to do the best.
I also would like to know how to set WOT advance. I've read where a 'dialback' timing light is used. Never heard of this before, but apparently necessary on getting best response from an HEI.
I know this is a lot of information requested, and all advice and explanations are appreciated.
Thanks ! !

'just wanting to learn since I can't afford shop prices'

[70cst]

Ok all you mini experts...suggestions for slowboy?

[Downtown]

Did you change the wire that supplies voltage to the HEI. The stock wire is a resistor wire and only supplies 9 volts. You only need to replace the section between the box on the firewall and the HEI. Don't know if that will help but the HEI is meant to have 12 volts.

Mark

[stich626]

Originally Posted by Downtown

Did you change the wire that supplies voltage to the HEI. The stock wire is a resistor wire and only supplies 9 volts. You only need to replace the section between the box on the firewall and the HEI. Don't know if that will help but the HEI is meant to have 12 volts.

Mark

x2 and if you still have your points dizzy you could match the weights you gonna use in the hei with the ones in the points same with the advance springs..
this will get you very very close..
also is the vacumn advance hooked up and working..test it by taking the cap off, and with a hand held vacuum pump see if the linkage moves when you apply vacuum, also does the advance can hold vacuum..

not knowing your engine specs it be hard to tell you start with x springs and y weights..

but matching the hei gear to what was under the points cap (weight and spring tention) you'll get quite close..

you can weigh the weights at any place that mixes paint home depot/ace/ect
to get a match or close..

after you get that all squared away.. gap the plugs 40-45,
set the timing save starting point is 12*btdc
disconnect the vacuum advance and plug the port on the engine, hook up a vacuum gauge to an nonported vacuum signal
start it up..
set the timing to 12btdc and then use the vacuum gauge the higher the vacuum the better,
go for a ride if it pings.. back off the timing a little at a time (2*) untill it's gone..

most mild to stock 350 v8s like 36-38* toatal timing (what you set at the crank turning the dizzy+the mechanical advance(springs and weights)+ the vacuum advance( the round can on the dizzy with the vacuum line going to it)this is where the dial back timing light comes in handy
if you've marked the balance with white paint so you can see the marks on it easier, you can roll the dial up ,starting at 36* and start the engine and run it up to 2500-3000rpm and adjust the dial on the timing light till you get a reading on the balancer of 0.., what ever you've dialed the light to is your total timing , most 350's drinking 87 swill will not like much more than 36-39*

now idle the engine zero the dial back light and turn the dial till you read 0 on the balancer, this will be your base timing and should be between 12-16* some set it at 18 and get away with it..

now you can play with when your advance come in or is all in..
the lighter springs bring the advance on earlier (to light and they can cause timing to bounce around at idle and just off idle)
most engines that are stock or mild like it all in by 2200-2500 some as high as 3000+rpm) every engines different
when you get the rpm that the engine likes it all in and the slope from the base timing to full timing. your engine will have part throttle crispness and power, great mpg..
good luck..

[truckster]

I dropped a stock HEI in mine - no internal mods. I ran 12v to the coil and used stock plugs for an HEI 350 - if I remember right, something like R44TS - gapped at .045, and timed it 10 degrees BTDC. It starts and runs great.

[stich626]

most will..

[slowboy]

hey guys...I didn't change stock wire...didn't know that...not exactly sure what to do...are you talking about replacing stock wire with a thicker wire
"truckster" - when you say you ran 12v to coil, exactly what/how did you do it...does this mean running a 12v wire from 'ignition' on fuse block to HEI coil...if so, does this mean the bigger wire allow more voltage

[oldblue1968chevy]

what guage wire do you use to power the HEI?

[slowboy]

don't know what gauge wire it is...all I know is it is the stock wire that powered the 'points' distributor

[Classic Heartbeat]

Run a 10 gauge wire from your ignition unfused plug in your fuse panel to the Dizzy. You must have 12 volts going into it. Like others have said the wire you are using now has between 7 and 9 volts. WES

[68 TT]

Originally Posted by Classic Heartbeat

Run a 10 gauge wire from your ignition unfused plug in your fuse panel to the Dizzy. You must have 12 volts going into it. Like others have said the wire you are using now has between 7 and 9 volts. WES

Also make sure it is an ignition on power source that is hot in start and run positions. If it is a constant hot source the HEI will over heat and fail when the engine is not running.

The HEI likes as much voltage as you can give it. I have used the stock resistor wire to activate a solenoid that gave the HEI full battery voltage when energized and it worked well.

[fastwillie 696969]

i would keep the points disributor and just add a msd 6 box and be done with it

[FLDBRED]

Year One and Summit both sell the wire you need! It has the proper fitting on both ends.Just follow your current wire to your firewall and remove it.Then use the new wire and proper hook ups!

[GASoline71]

The 12v wire to the HEI needs to be a "dedicated" 12v source wire. Not spliced in from a heater motor or electric choke or anything.

Also... ditch the E3 snake oil plugs. Get some NGK's or AC Delco plugs.

Gary

[Katrina/10]

The original wire between the firewall block and the coil is a resistor wire which drops the voltage. Cut it off and replace it with a 12 guage wire.

[68 TT]

I grab the HEI power wire off of older front wheel drive cars at the wrecking yard when ever I can. You can get a six foot long piece of heavy gauge wire with the right connector on it to snap onto the HEI this way. There is enough wire length to get it to the fuse block or pretty much anywhere else yo could want to connect it. Sometimes they have the tach connector too.

It also is nice because you can connect it directly to the battery to trouble shoot the system if you are having problems.

[LONGHAIR]

stich626, you seem to be making a lot of assumptions about "stock" HEIs. They are NOT all the same. There are/were dozens of different advance curves (and limits) to each of the different types of advance.
Some units had less centrifugal advance and used more initial, others were just the opposite, having a lot of centrifugal advance built into them.
The vacuum canisters had their differences too. Not only did the amount of vacuum required to make them work vary,so did the actual amount of advance that they could pull.
Most of these issues were because of "ported vacuum" emissions tuning....which means that most of the stock HEIs out there are in this group.
Just dropping in any old junkyard unit and connecting it to full vacuum will likely result in a pining/rattling mess. Leaving it connected to the ported source is leaving drive-ability and fuel economy on the table.....besides the fact that it would be 25 years old.
An up-dated new unit with known specifications is a far better bet.

What it comes down to is that you have to know what your distributor is doing, but testing is not the easiest thing to get accomplished. Since there are so few of those old Sun machines left, it pretty much has to be done in a running engine, which is going to mean several R&R sessions with the distributor and a good timing light (after first verifying and marking TDC)

[GASoline71]

The old HEI's with a "4 pin" module are the best for these old trucks.

Gary

[68 TT]

Originally Posted by LONGHAIR

...Just dropping in any old junkyard unit and connecting it to full vacuum will likely result in a pining/rattling mess. Leaving it connected to the ported source is leaving drive-ability and fuel economy on the table.....besides the fact that it would be 25 years old.
An up-dated new unit with known specifications is a far better bet.

What it comes down to is that you have to know what your distributor is doing, but testing is not the easiest thing to get accomplished. Since there are so few of those old Sun machines left, it pretty much has to be done in a running engine, which is going to mean several R&R sessions with the distributor and a good timing light (after first verifying and marking TDC)

I completely agree. The new one I have also has an adjustable vacuum advance so it can be easily altered when needed.

If you can't afford a new higher quality HEI then getting one out of a mid 70's non-catalytic converter truck will give you the best chance that it will work fairly well in your older truck without the need for changing the vacuum advance mechanism. Just testing different springs for the mechanical advance may be all that you need to do to make it work for you.