Gm hei

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harvenator

harvenator

A fish called Wanda
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My old TP70 ignition CPU seems to have finally given up. It was installed by the PO when the car had a /6. Since doing a V-8 conversion I've had nothing but trouble from the ignition system. I finally got a new Proform electronic distributor and wired up a GM HEI unit with a NO Ballast required coil.
The car starts but won't run below 1500 RPM. There are no vacuum leaks, the carb is new as is the fuel pump and filter. These are all items I've replaced trying to get this thing right.
I had too crank a little more advance in the dist. to start the engine and when it's running shows 30 deg at 1500 with no vacuum advance hooked up.
Alternator is putting out about 14.5 volts. Regulator is mechanical and only shows 7 volts but now I realized when I checked it I had the probes on IGN and FLD. I think I should have checked each to ground? I'll try that tomorrow.
In the mean time, I'm looking for suggestions as to what the culprit could be.
 
Whats the pn of the proform dist?
Is the Hei unit the mid 70s 4 pin? Is it secured to a heat sink with thermal paste? Is it grounded thoroughly? Check voltage at coil +, and at hei +. Is the hei wired correctly?
How old is the timing chain and gears?
 
Try swapping the distributor wires and rechecking timing. Oddly, one works and the other doesn't. In the HEI conversion on my Duster, the correct connection never let the ignition rev more than 1300 or so, and by switching the connection, allowed free revving and starting.
 
Heat sinked with paste, grounded, 4 pin HEI, newly rebuilt motor (runs good with friends pertronix ignition)
 
Big D said:
Try swapping the distributor wires and rechecking timing. Oddly, one works and the other doesn't. In the HEI conversion on my Duster, the correct connection never let the ignition rev more than 1300 or so, and by switching the connection, allowed free revving and starting.
Click to expand...


the reason for this is that it changes relative rotor timing, called "rotor phasing." The change in the pickup pulse moves the timing and the spark now longer fires when the rotor/ plug towers are aligned.
 
Switching the wires did nothing. I'm getting about 13.5 to 14 v to + side of the coil. I've even tried switching coil wires around. Took the module back to AutoZone and watched as he checked it about 8 times with no faults noted.
 
Sorry -- every time it dies............
I'm also using graphite wires. No copper.
 
Does it actually run backwards or diesels when turned off? The later would more be either too much retard (closer to TDC) or overly rich mixture and possibly preignition. Make sure timing is corrected before working on anything else. If your friend's Petronix ignition worked, would that be the pickup or the whole distributor? There could be a potential fix if the Petronix ignition worked while yours doesn't. That would be my focus anyway.
 
67Dart273 said:
the reason for this is that it changes relative rotor timing, called "rotor phasing." The change in the pickup pulse moves the timing and the spark now longer fires when the rotor/ plug towers are aligned.
Click to expand...
Wouldn't this just require a reset of the timing after the plug wire were reversed? I have noticed that the HEI get's quite warm when operating and I'm always looking for the cooler range of operation. One write-up of the HEI conversion says that the wires need to be correctly placed: "Make sure you don't get the magnetic pickup wires confused. If they are wired backward, it will result in your timing being off by over 10 degrees. I took great pains to include the proper polarity in the GM HEI CONVERSION schematic above. On my 85 Dodge Ramcharger w/ the 318 engine, the positive magnetic pickup lead is the ORANGE wire that leads to the exposed pin on the distributor side of the connector. The negative lead is the shielded pin. On the HEI, the pinout is as follows:

B = Battery (this pin goes to a KEY SWITCHED 12v supply lead ONLY, not directly to the battery)
C = Coil (this is the coil negative wire, ground is supplied through the HEI module)
G = Negative Magnetic Pickup lead (on the GM engine, G stands for green wire)
W= Positive Magnetic Pickup lead (on the GM engine, W stands for white wire)"

This comment forced me into believing that the correctly connected wires would just mean an adjustment to the timing and all would be better. But I had not found success using this methodology. I had shrugged it off as someone's vehicle working using this connection and mine being different enough for it to not work. But the engine runs quite well with the current, and backwards, wiring connection so I'm staying with it for now.
 
The thing is you MAY be able to get the engine to run by changing the timing but the fact is that the spark (when pickup is connected wrong) is producing the spark when the rotor/ towers are not correctly lined up.

If you Google "rotor phasing" this has taken on a life of it's own. You never used to hear about it until computer controlled advance came along on older engines still using a distributor WITH NO advance mechanism.

Some guys take an old cap and cut holes in it so you can check rotor phasing:

An MSD pdf on the subject:

http://www.msdignition.com/uploaded...port/frm28392_tech_bulletin_rotor_phasing.pdf

Much of this has also cropped up because of crank triggered ignition. If you have a race car with a locked crank trigger, you must get the distributor "sync" correct (phased) with the crank trigger.

If your cap shows signs of damage to one side of the plug towers (carbon tracking) this would be an indicator of a problem. It can also cause crossfire, as well as reduced spark to the plug where it belongs.
 
I'm fixed!!!!!!!
The other day I went to a salvage yard and picked up an actual GM module out of a distributor that was laying around. I installed it and started the car, idled it down to 800 RPM reset my timing and carb settings and took a drive. It starts faster than before, idles smooth and runs out just fine. Still have to pull the dizzy to find out why I'm not getting mechanical advance but at least it's driveable.
Thanks for all the input guys.
Lesson learned? Just becase the tester at the parts store says something is good doesn't necessarily make it so!!
 
harvenator said:
I'm fixed!!!!!!!
The other day I went to a salvage yard and picked up an actual GM module out of a distributor that was laying around. I installed it and started the car, idled it down to 800 RPM reset my timing and carb settings and took a drive. It starts faster than before, idles smooth and runs out just fine. Still have to pull the dizzy to find out why I'm not getting mechanical advance but at least it's driveable.
Thanks for all the input guys.
Lesson learned? Just becase the tester at the parts store says something is good doesn't necessarily make it so!!
Click to expand...

Very good. Glad to hear it was a small dollar item.
 
What the heck. Was your existing hei module all old and shot or something?
Man, one time I used two hei modules to get a 4 cyl kawasaki running. The factory elec module was 475.. heheheh. 27 bucks fixed my bike.
 
Nope, it was brand new. Bought it at Autozone. I'm becoming increasingly frustrated with the quality of their parts and am almost ready to use them strictly for mechanical parts only. Their electrical stuff sucks. I also went through 2 rebuilt dizzys before giving up and ordering a Proform from someone else.
I've heard that their electrical parts have about a 25% failure rate and they feel that's acceptable.
 
Autozone sucks - my view. It is just bottom of the barrel reman stuff in general. Surprisingly I got a basic clutch, pressureplate and clutch slave throwout bearing for my 96 ranger (4 years ago) and it is holding strong for 25k thus far. These days I will not buy anything from autozone other than armorall and shop towels. I like Napa and second Oreilys. Napa had my 4wd front hub mechanisms for my ranger in stock, the good brand ones!
 
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