HEI distrib problem under load

[Gene King]

Hey guys,
I've got a carb'd 305, was running good for years but I've got a stumbling/hesitating/dying problem only when the engine is under load starting today. Narrowed it down all afternoon to something inside my hei distributor.
Do you guys know of something inside there that would cause that problem I should look at first tomorrow? I've never delved into them.
Specifically it's an Accel 140005 distributor.
Thanks a lot

e: 1 more thing my last test run of the day my tach stopped working too

 

[Bextreme04]

The later 305's have an ESC system that is notorious for causing issues under load. It uses a knock sensor to pull timing when it senses detonation. When this system has issues, this is often the behavior that is seen.

 

[Gene King]

My distributor would have more than 2 connections if it had ESC aye? I've just got power and tach plug-ins. I ran a wire direct from the battery to the distributor today also to test that, it's getting good power.
It's kind of a Frankenstein engine, 1977 block covered in bolt-ons.

 

[Gene King]

I've kind of got a hunch that vacuum advanced is involved since that's the only way my distributor cares about load as far as I can see.

 

[AuroraGirl]

I've kind of got a hunch that vacuum advanced is involved since that's the only way my distributor cares about load as far as I can see.

Your distributor also has advance weights, although, they probably wouldnt distinguish between load, but if they are misbehaving in a consistent way, maybe under load the falling on face/issues are way more evident, but here let me show you something

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here is a 78 sbc 400 ci distributor, no ESC, for reference,

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heres various SBC distributors, all HEI, can you confirm they are 1) clean on the inside, not rusted like these, 2) your coil is not like the 2nd or 4th on the second photo, 3) the components on the distribuor dont have bad wiring or connectors on the inside? this is with the top plastic shell off the cap over the coil and the rotor taken off the distributors with the cap off. while cap is off, check your rotor screws. do they look burnt or arced to? they make plastic screws that can help with that issue where it may happen

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See how I cleaned up one of those? If you play with them(centrifrugal weights) the ones rusted dont move very much or they dont kick out when the distributor is turned quickly(a quick twist with the hand should be able to kick them out usually), and they dont return to center if they do kick out or you push them out. The one I cleaned up it will nicely and smoothly do all the aforementioned. My truck, personally, had an issue where the weights would kick out but occassionally stick and cause my truck to high idle and it took a lot of jabbing to unstick and it made starting the truck, if they were kicked out, damn near impossible because my distributor was advanced.

for funsies, here is my buick (350 buick, 1977)

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i show this one because its easy to access the distributor on the buick because its right up front. its a reach to get to my trucks which i need a ladder for and stretching over the engine bay

 

[AuroraGirl]

nvm i found a pic of my trucks

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[Octane]

My bro had a car with esc and this sounds like the problem and solution to it with the bypass.But we never found a shop that could fix it.They all seemed to think in those days that there was a bad ground somewhere.

 

[AuroraGirl]

I found this online:

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I had a problem with my 86 C20 305-H engine. It could start and run fine and just suddenly die out, sometimes start right back up or take a couple hours to get restarted. After several weeks of this nonsense (and getting very good at getting those half turn dist. cap latches off), I did some checking. There is a power feed to the spark control unit under the dash that comes off of the pink (hot) wire to the distributor. The pink wire clips into the connector for the feed, which in turn clips into the dist. cap. What had happened was the feed for the Spark Control was shorting out somewhere, killing the spark. I talked to some Chevy mechanics at my dealer about this and they told me how to bypass the spark control computer and keep the original distributor, something they claim is done quite often.

First thing to do is unhook the spark control computer lead from the pink wire and hook the pink wire directly to the dist. cap. Make sure you plug it into the cap at the BAT terminal. The second thing is to locate the 4 wire connector that feeds into the ignition module. There's a brown (D), green (C), white (B), and black (A) wire there. The letters in () are on the black clip that the wires come out of. You cut the green (C) and black (A) wires between this clip and where they go into the distributor. Then all you need to do is solder the 2 cut leads from the dist/ignition module together, i.e. the green and black ones, (make sure to tape the exposed wires) and now your HEI distributor will function just as a pre ESC model does. I did this and it has been running fine for well over a year now.

credit to a Dan from http://www.73-87.com/7387garage/drivetrain/escrepl.htm that was his write up and image it seems. if you need to do that to yours, hopefully that makes sense. I have no vehicle with this system nor ever done it myself, so I cannot offer any personal help on the matter.

 

[RoryH19]

I found this online:

You must be registered for see images attach

I had a problem with my 86 C20 305-H engine. It could start and run fine and just suddenly die out, sometimes start right back up or take a couple hours to get restarted. After several weeks of this nonsense (and getting very good at getting those half turn dist. cap latches off), I did some checking. There is a power feed to the spark control unit under the dash that comes off of the pink (hot) wire to the distributor. The pink wire clips into the connector for the feed, which in turn clips into the dist. cap. What had happened was the feed for the Spark Control was shorting out somewhere, killing the spark. I talked to some Chevy mechanics at my dealer about this and they told me how to bypass the spark control computer and keep the original distributor, something they claim is done quite often.

First thing to do is unhook the spark control computer lead from the pink wire and hook the pink wire directly to the dist. cap. Make sure you plug it into the cap at the BAT terminal. The second thing is to locate the 4 wire connector that feeds into the ignition module. There's a brown (D), green (C), white (B), and black (A) wire there. The letters in () are on the black clip that the wires come out of. You cut the green (C) and black (A) wires between this clip and where they go into the distributor. Then all you need to do is solder the 2 cut leads from the dist/ignition module together, i.e. the green and black ones, (make sure to tape the exposed wires) and now your HEI distributor will function just as a pre ESC model does. I did this and it has been running fine for well over a year now.

credit to a Dan from http://www.73-87.com/7387garage/drivetrain/escrepl.htm that was his write up and image it seems. if you need to do that to yours, hopefully that makes sense. I have no vehicle with this system nor ever done it myself, so I cannot offer any personal help on the matter.

I've done this exact same thing and it does work.
However just make sure the esc is still in place. By now most of them have been removed or at least bypassed.

 

[RoryH19]

Your distributor also has advance weights, although, they probably wouldnt distinguish between load, but if they are misbehaving in a consistent way, maybe under load the falling on face/issues are way more evident, but here let me show you something

You must be registered for see images attach

here is a 78 sbc 400 ci distributor, no ESC, for reference,

You must be registered for see images attach

You must be registered for see images attach

heres various SBC distributors, all HEI, can you confirm they are 1) clean on the inside, not rusted like these, 2) your coil is not like the 2nd or 4th on the second photo, 3) the components on the distribuor dont have bad wiring or connectors on the inside? this is with the top plastic shell off the cap over the coil and the rotor taken off the distributors with the cap off. while cap is off, check your rotor screws. do they look burnt or arced to? they make plastic screws that can help with that issue where it may happen

You must be registered for see images attach

See how I cleaned up one of those? If you play with them(centrifrugal weights) the ones rusted dont move very much or they dont kick out when the distributor is turned quickly(a quick twist with the hand should be able to kick them out usually), and they dont return to center if they do kick out or you push them out. The one I cleaned up it will nicely and smoothly do all the aforementioned. My truck, personally, had an issue where the weights would kick out but occassionally stick and cause my truck to high idle and it took a lot of jabbing to unstick and it made starting the truck, if they were kicked out, damn near impossible because my distributor was advanced.

for funsies, here is my buick (350 buick, 1977)

You must be registered for see images attach

i show this one because its easy to access the distributor on the buick because its right up front. its a reach to get to my trucks which i need a ladder for and stretching over the engine bay

Hey, since you have an entire salvage yard, do you have any diesel squares? I need the radiator hold downs at the top.

 

[Rusty Nail]

Lmfao

 

[AuroraGirl]

Hey, since you have an entire salvage yard, do you have any diesel squares? I need the radiator hold downs at the top.

no sadly no diesels seem to have run through my grandpas life it seems. Like, the closest thing is a oliver 6 cylinder that has the same block and a bunch of internals if it was diesel, kerosene, distillate, gas, etc just depended on how it was setup. unfortunately it was gas, so boring. I learned from my uncle that he got really frustrated with a diesel towed generator that he had once and kinda swore off em so everything pretty much was gas around here.

If it helps understand, he was very much the kind of person to take a joke the wrong way and completely change his line of work, routes he drove to places, avoid events, paint his **** a different color(as to not have anything the same as the person), and quit smoking and pick up chewing to disassociate because of it.

So diesel was like the guy who said the wrong thing on the wrong day


But I do have the top plate hold for a 400 sbc with HD cooling which had the radiator Almost the size of the diesel. no dice tho

 

[RoryH19]

no sadly no diesels seem to have run through my grandpas life it seems. Like, the closest thing is a oliver 6 cylinder that has the same block and a bunch of internals if it was diesel, kerosene, distillate, gas, etc just depended on how it was setup. unfortunately it was gas, so boring. I learned from my uncle that he got really frustrated with a diesel towed generator that he had once and kinda swore off em so everything pretty much was gas around here.

If it helps understand, he was very much the kind of person to take a joke the wrong way and completely change his line of work, routes he drove to places, avoid events, paint his **** a different color(as to not have anything the same as the person), and quit smoking and pick up chewing to disassociate because of it.

So diesel was like the guy who said the wrong thing on the wrong day


But I do have the top plate hold for a 400 sbc with HD cooling which had the radiator Almost the size of the diesel. no dice tho

No problem

 

[AuroraGirl]

also this is a dumb seeming comment, but KISS is always watching and present..

how are your plugs and wires?

Ive had a bad wire that i presume was internally too resistive from factory and when i Put it on, I had a cutout, miss, but more from the lack of participation of a cylinder rather than improper timing of the combustion, and found my wire , which was new, worked fine at idle but if i gave the throttle some go, it would arc out of the middle of the wire onto my engine hoist hook

ignore the random paint doodles on the engine
earlier this year i was marking fasteners that I suspected were loosening from vibration and the markers and the atmospheric conditions made a perfect scenario in which i think the paint fumes made me a little high because i ended up doing that for an hour and eventually I was like "what the **** am i doing" and got some air. It was a weird day.

ANyway, see the hook, my wire was closer to it and defective, it like melted the wire sleeve at the spot too, weird. See the coil end? You have a cap of course, but the idea is the same. The nub the wire is on needs to be air tight, secured tightly to the nub on the tower, and also clean of corrosion. any corrosion is resistance, any arcing or carbon tracking(ionization from high voltage spark jumping the gap in the closed space, etching carbon into the metal or just slowly zapping away metal) is resistance, any gap is energy spent to cross the small air space instead of conducting through the wire and cap, and that energy is less vroom vroom from engine and it can be a situation where load/rpm it gets worse, but handles idle ok. improperly pulling wires(recommend the pliers) is great at separating the end on the wire so it becomes loose fitting. Use some dieletric grease to seal out 1) moisture 2) air. you want there to be no place for air since its displaced by the grease. which also keeps it easier to remove especially on plugs that are smooth on the porcelain. the ribs are common on our trucks, which btoh can be a bitch to pull off. Also then finally, the plug.

A bad plug doesnt let the zap zap make the vroom vroom.

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[Gene King]

Thanks a lot AuroraGirl I'm about to go out and monkey with it, will reference those photos.
The problem is definitely more severe than just running on 7 cylinders from a bad plug or wire.
It's erratic but sometimes it loses ignition completely for a second, then gas will build up in the exhaust and make a hell of an explosion sound when it does fire again.
I can't get it to do it in the driveway though.
Anyway I'm about to take the top off that distrib and see what I can see