any gm H.E.I. gurus out there?

[Deaf Bob]

Here is a WILD idea...
Try a points dist? You oughta have one laying about?

[fatguyzinc]

Here is a WILD idea...
Try a points dist? You oughta have one laying about?

i just may have to do that next...although the roundy round guys run step-up boxes
to get 16-18v into an HEI and they love it, and i would think points would fry WAY
before that. but then again i aint getting nowhere like this !

i may just "de-evolutionize" it and try that. i will keep you posted, and thanks to all
who have come up with suggestions.....

[Runner1972]

Posted the issue on another forum for you, could it be a possible short with the Accessory on the lock cylinder?:



to completely agree with hot rod jackson.. a few images
http://i.imgur.com/XQr8zFI.jpg the ground strap.. the corner of the ignition coil laminations must be cleaned of paint for this to conduct properly.
http://i.imgur.com/M02Z7cs.jpg the RFI wiring harness.. new numbers listed to make it easier to find.. see the hold down screw.. that grounds the black wire that plugs into the ground strap above. if that ground screw is loose.. there will be blown modules and blown coils.. i have found broken wires from things rubbing the RFI harness on the outside of the distributor..
http://i.imgur.com/niLSrHq.jpg blown coil. these sometimes sound like shot guns going off under the hood..
WHY.. when the spark jumps the gap into the cylinder head.. where does it go? thru to the intake or block.. up thru the distributor housing , thru the RFI harness.. the folded metal ground strap. the coil laminations and then to the black wire to the coil..
with an open ground connection to the coil laminations.. crazy high voltages can build up in the laminations until it flashes over to the yellow or white wire when the module power transistor is turned on and grounding the coil... this is why it blows the module. perhaps 100,000 volts comes flying thru the power transistor that is rated for probably 20 or 30 volts max.
two more things.. HEI modules have 2 hold down screws.. you will notice that that one of the module hold down areas has a solder joint .. that is where the power transistor is hooked to ground.. right thru the screw..
there are a few applications where GM actually put a steel plate over the ignition module to prevent high voltage strikes from the tip of the rotor from blowing out the module.. i usually find those on 4.5 and 4.9 caddy motors from the late 80s and early 90s and they are a good idea to install.
heat sink grease is as hotrodjackson posted it critical.. it transfers the massive amount of heat generated by the power transistor turning on and off to the distributor housing..
running tests 1 thru 4 and 6 is a good idea on that corvette .. http://i.imgur.com/Mo57rdb.jpg test 5 is to a positive power stud but i don't recall where or if they were installed in a 77 C3. i usually end up working on crossfire C4 models ..

[fatguyzinc]

[COLOR=#4D5763][FONT=verdana]Posted the issue on another forum for you, could it be a possible short with the Accessory on the lock cylinder?:

thank you, i will get a multi meter and try these tests next....

[fatguyzinc]

Here is a WILD idea...
Try a points dist? You oughta have one laying about?

did it. car started and ran fine....
several times even !

and then i went for a test drive around block.
came home 2 hours later on a tow truck.
dead distributor. AGAIN. new set of points &
condenser got it fired again--for maybe 30 seconds.

then it killed those too.

anyone need C3 vette parts?
i really think im going to strip it shortly.

[STINEY]

Did you read SBG's post on his FJ40 thread where he had an alternator with enough front bearing movement that it was taking out HEI modules due to incorrect AC/DC rectification?

Not sure how that would translate to points failure, but I'm sure condensers and points don't appreciate AC voltage, even in minor quantities.

Might be something to check?

Sure is a bizarre problem you are chasing, good luck!

[fatguyzinc]

Did you read SBG's post on his FJ40 thread where he had an alternator with enough front bearing movement that it was taking out HEI modules due to incorrect AC/DC rectification?

Not sure how that would translate to points failure, but I'm sure condensers and points don't appreciate AC voltage, even in minor quantities.

Might be something to check?

Sure is a bizarre problem you are chasing, good luck!

yep, changed the alternator to a known good one AND
another reman just in case. same-u/same-u....
thanks for the luck, i really need it with this one !!!

[fatguyzinc]

as much as i HATE to do it, i think im going to start stripping the 77 vette
this coming weekend. i just cant find whats killing distributors and i refuse
to "pass it on" to the next poor b@st@rd...

sucks, this is the first time ever i havent been able to figure out a problem.
but i cant pay $300 registration and $259/year insurance on a car i cant
drive. and since its left me stranded EVERY single time i drove it in the
last 3 months---strip it is. anyone need anything? clean title too....

[malc]

One last try......have you traced all the relevant wires to check for shorts or other suspicious splices ?

[Dan Barlow]

I know it sounds crazy but what about a Painless full or just a under hood wire harness ?

[Deaf Bob]

It's gotta be simple..

[fatguyzinc]

One last try......have you traced all the relevant wires to check for shorts or other suspicious splices ?

yep. numorous times. too many to count. been over every inch more than once.
to say i am frustrated is a gross understatement...

[fatguyzinc]

I know it sounds crazy but what about a Painless full or just a under hood wire harness ?

i just cant put any more $$$ into this car.
we have 3 vettes counting this one so no
big loss. i just hate to do it.

[fatguyzinc]

It's gotta be simple..

yep. i agree. but whtever it is i just havent been able to find it.
and once the wife brings up the "no sense throwing good money
after bad" quote, you know youre in trouble.....

[SuperBuickGuy]

Heat has been killing my HEI modules.... yeah, Heat. GM put a vent in later ones, and I wonder if you drill a hole in the base of the distributor (to allow it to breath) whether that would solve the issue? Alternatively, (and i'm not looking back to see if this was suggested) you can eliminate the module by using a MSD box...