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1973 DeVille, 1975 Hearse
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Discussion Starter #1 (Edited)
With the weather about to turn, I patched up the holes in the gas tank on my ol’ rusted out '73 DeVille and filled it back up to hit the streets. However, I’ve run into a problem that’s left the car holding down the driveway.

The car runs perfectly fine when I first start it, but as the engine approaches operating temperatures it starts to miss very badly. I put a test light on each plug wire, and when the engine is warm, only the rear spark plugs on either side and getting any spark (these wires are adjacent to each other at the top of the tilted distributor). To add to the weirdness, if I hold the engine at a higher RPM after it’s warmed up, all plugs start to spark again and it runs just fine. Let it drop back down to the normal idle and it starts to miss again.

All the spark plugs are new, and I just replaced the wires last year. I even shuffled the wires around to make sure six hadn’t failed all at once in some bizarre fluke. I replaced the cap and rotor and saw no improvement. I applied suction to the vacuum advance on the distributor at idle and saw no change. And I left the same vacuum line disconnected from the carburetor as I revved the engine to see if it would continue to miss at high idle; it ran fine even with that vacuum line off.

So at this point, the only thing I can see it being is either the ignition coil, or the distributor itself. But if it were the coil, I’d think the lack of spark would be more sporadic instead of the same six cylinders always missing and the same two always firing.

Before I throw anymore money or time at my guesses, I figured I’d consult the experts here and see if anyone had any ideas. This car does not have the HEI distributor; it has the separate cylindrical ignition coil. It’s has a 472 if that’s of any significance.
 

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95 FWB 81SDV 96 FWB 94 Fleetwood
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I have been around a long time and started out with these points systems. What I have found way in the past that this could be happening. The points are screwed down to the plate in the distributor. This plate moves back and forth with the vacuum advance. Well on the bottom side of that plate is a ground wire that goes from the points plate to the body of the distributor. This wire is broken, that would account for it working better when reved up .. The distributor has to come out and taken all apart to fix that wire.
 

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Discussion Starter #3
Thanks for the reply, drmenard. I took off the cap and located the ground wire you were referring to. I grabbed a flashlight, got a good angle on it, and gave it a visual inspection. It looked to be in good shape. I couldn’t quite see where it connected to the underside of the plate, so I got a little hook and tugged the wire around in a few directions to make sure that connection was solid. Everything felt good.

Still, for good measure, I added a new ground wire just to be sure. I mounted one end in the same spot as the original wire by the vacuum advance, and the other end on top of the plate where the points are screwed down. Fired the car up (cold start first time today) and it ran poorly even while cold. Not two-cylinder poorly, but very bad. Even revving up the engine didn’t make it smooth out. Shut the car off, took out my new ground wire and started it back up. Same problem.

I figured I had disturbed the position of the points when I added the new ground wire (even though I was very careful not to). I started checking spark on each wire to see if certain cylinders were failing or it was consistently bad across the board, but while I was doing this, the engine got warm enough to revert to the two-cylinder-only problem. But here’s a kicker, once the engine was in this state, I revved it up, all eight cylinders started firing, and everything smoothed out nicely…even though not ten minutes before revving the engine didn’t help at all.

Since the engine was back in “two-cylinder mode”, I added back my custom ground wire one more time just to see if it helped at it. No difference, so I took it back off again.

I did perform one more test today I hadn’t before. I took my test light, connected it to the coil, and then grounded it straight to the body instead of connecting it to the distributor. When I cranked the engine, it would consistently flash twice and then go dead for a bit, which matches the two-cylinder firing condition. So my question there is: Does the distributor control when the coil sparks even if the main wire running from the coil to the distributor is disconnected? If it doesn’t, I feel like this suggests the coil is bad.

I didn’t get a chance to run this same test on the coil in a cold start condition because it got dark out before the car cooled back down.
 

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Have you adjusted the points? It sounds like your problems are in the distributor. Each rotation of the rotor opens and closes the points 8 times to fire each cylinder . Is the adjustment way off?
 

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Discussion Starter #5
I'm starting to think it might be as simple as that.

I was hesitant to mess with the points because I've never done such a thing and I didn't want to make matters worse since it's such a precision adjustment, but I just looked up the process and it appears to be remarkably simple. I was surprised to find that most sources recommend replacing points about every 6,000 miles. That seems awfully frequent. I think I'm going to pick up a set of feeler gauges and try adjusting the points Thursday (next non-rainy day).

For what it's worth, I'll post my experiments from this evening. Hooked the test light up to the coil and grounded it again while cold cranking the engine. Got the same double flash and then dead gap pattern as yesterday when hot. Hooked the coil back up and started the car. Ran pretty much fine so I shut it off before anything warmed up at all. Did the grounded coil test again and found a consistent spark while cranking. Seemed odd that the condition changed just like that. Started the car, let it warm up until it started missing, then did the coil test again; back to the double flash and dead gap.

I'm also thinking the lack of spark isn't related to the engine temperature at all, just the engine speed. The idle just doesn't drop low enough when cold for the issue to occur. I'll test this theory later by starting the engine cold and shifting into gear to force the engine speed down.

Anywho, I'll report back how things go with the point adjustment in a couple days. But I'm pretty sure my lack of experience with points is the going to turn out to be the real root of my problem here.
 

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GET A DWELL METER!!! Use the 1/8 allen key insert to adjust while the car is running to 30 deg as per the meter. Then check your timing as per the manual.
 

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Discussion Starter #7
So...all fixed. It was the points gap. I feel kind of dumb that it was something that easy, but on the other hand, I've never dealt with points before, so I guess you don't know what you don't know.

I did end up using a dwell meter. The angle was about 38 degrees when cold and by the time it warmed up, it was about 40 degrees (so I'm assuming the as it warmed up, the points or the metal surfaces they were attached to were expanding ever so slightly and pushing the car over the edge where it wouldn't run).

I increased the gap while the car was running until the dwell angle was right at 30 degrees and now the car runs perfectly. Didn't have to mess with the timing at all. I went to check the gap just to see what it was, but the points seem oddly placed on this distributor; I couldn't find a way to get my feeler gauges at them.

I've had the car running out in the driveway for about twenty-five minutes with no issue, so I think the only test left is to make sure it still runs when cold.

Honestly, this is the exact opposite of what I expected. I figured the gap was too wide. Since the car ran fine a year and a half ago, it seems odd to me that the gap would get smaller over time.


Oh, and not that it matters now, but I did test to see if the failure was related to engine speed or temperature. When cold, if I dropped the RPMs down the the normal warm idle speed, the car still ran fine, so it was the heat that was making the distributor fail.


Thanks to both of you for your help.
 

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Your distributor cap should have a window in it with a small tin door. Pull that up and you an use a 1/8 Allen key wrench to adjust the dwell while the car is running. If you don't have the window, please get a proper AC Delco cap. It will make your life easier.
 

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Most people swapped out the points for HEI distributors.
Less maintence, better performance & more reliable.
Points get burnt from normal use.
It's nothing more than a primitive DC switch.
Switching DC is very hard on contacts.
Figure it makes & breaks the coil connection 4 times per revolution.
At 3,000 RPM that's 12,000 make & breaks of the circuit.

Points get burt, corroded, & out of adjustment. They bounce at high RPM causing a miss.
Points coils are rated around 20kv where HEI is around 40kv with performance coils were around 65kv.
Can't put a higher kv coil without burning the points up faster.

Back in the day they had duel points & electronic point conversions for performance & extended service.
Delcos HEI was the best stock electronic ignition to come out in the 70's.
Only to be out done by later electronic spark control (with knock sensor) HEI's in the 80's.
The full cumputer controlled ignitions of the 90's.
Finely current time when GM used distributerless ignitions finely on the V8's with 1 coil per cylinder.

If I could drop an HEI in the LT1 I'd do it tomorrow. But no such luck without changing the engine block.
You can buy the entire kit new for around $150 with coil, cap, rotor, plug, Ign wires, & distributor for around $150.
More for performance brand names. Or a used core for around $70.

I remember back in the 70's people would carry an extra set of points in the glove box or tool box.
They were that bad.
It's from the same era where a car with 100k miles was considered finished.
Where the front & rear drum brakes were adjusted with each oil change.
And a tune-up was way more involved then just throwing in plugs.
 

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Most people swapped out the points for HEI distributors.
Less maintence, better performance & more reliable.
Points get burnt from normal use.
It's nothing more than a primitive DC switch.
Switching DC is very hard on contacts.
Figure it makes & breaks the coil connection 4 times per revolution.
At 3,000 RPM that's 12,000 make & breaks of the circuit.

Points get burt, corroded, & out of adjustment. They bounce at high RPM causing a miss.
Points coils are rated around 20kv where HEI is around 40kv with performance coils were around 65kv.
Can't put a higher kv coil without burning the points up faster.

Back in the day they had duel points & electronic point conversions for performance & extended service.
Delcos HEI was the best stock electronic ignition to come out in the 70's.
Only to be out done by later electronic spark control (with knock sensor) HEI's in the 80's.
The full cumputer controlled ignitions of the 90's.
Finely current time when GM used distributerless ignitions finely on the V8's with 1 coil per cylinder.

If I could drop an HEI in the LT1 I'd do it tomorrow. But no such luck without changing the engine block.
You can buy the entire kit new for around $150 with coil, cap, rotor, plug, Ign wires, & distributor for around $150.
More for performance brand names. Or a used core for around $70.

I remember back in the 70's people would carry an extra set of points in the glove box or tool box.
They were that bad.
It's from the same era where a car with 100k miles was considered finished.
Where the front & rear drum brakes were adjusted with each oil change.
And a tune-up was way more involved then just throwing in plugs.

So what?

My 1968 DeVille Convertible with points & condenser starts in 1/10 of a second when cold and runs quite smoothly. I don't race with it and I change the points every year or so. I keep a spare ignition kit in the trunk. It all fits in a small box.

A GM HEI won't fit because of the dual AC pulleys and a pertronix is no more reliable than P&C and when (not if) the pertronix goes bad, you're done unless you have the replacement parts in the car with you. The points will let you know when they are getting worn, and you can even file them clean once or twice.

Cadillac rear brakes have auto adjusters and 68 came with front discs (as an option, standard in 1969).

I have about 181,000 on the 68. All Original cast iron (overhauled), except the water pump.

Yes the HEI was great and the later distributorless ignition was even better. the mid 90s LT1 opti spark could have been great if it wasn't for its placement directly under the water pump, It is a good performing system as long as you don't get it wet.

But a good set of Delco points is still fine in the 1973 and older cars.
 

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Discussion Starter #11 (Edited)
Went out and cold started the car. No issues, so it looks like I'm good to go. Drove down to the gas station and filled it up...my patches leak. But that's a problem for another day. At least they're better than the two-inch gaping holes that were there last year!

Your distributor cap should have a window in it with a small tin door. Pull that up and you an use a 1/8 Allen key wrench to adjust the dwell while the car is running.
Yep, that was how I did it. That little door was a great idea on GM's part.


Points vs electronic ignition seems kind of like carburetors vs fuel injection.

I stopped buying fuel injected cars because (from my experience) the fuel delivery systems fail instantly without warning, leaving you stranded. When carburetors start to go, you have plenty of warning to get things fixed. I've never had a carburetor fail in such a way that I couldn't get it running well enough again to at least get myself back home. I believe the first post I ever made on this forum was when I was trying to fix something fuel-related on my fuel injected '79 Eldorado. Never did fix that car. Sold it to a guy who had to spend close to $1,000 to get the fuel injection working again.

Given that this DeVille is the only car I drive with points, I don't have much of an opinion on points vs electronic ignition yet. Though I'm sure I'll develop an opinion in time. I will say I've never had a GM HEI distributor fail on me. But the "brain box" mounted on the fender in my '77 LTD failed on me once (I'm assuming that'd be considered part of the electronic ignition system). The car would die at random and then start again a few minutes later. It did this a few times before it eventually quit altogether. Luckily I was home when it completely failed. Cheap and easy fix, but the potential to be left stranded by it is a bit annoying. My uncle said he always kept a spare brain box with him in his Lincolns just in case.
 

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So what?

My 1968 DeVille Convertible with points & condenser starts in 1/10 of a second when cold and runs quite smoothly. I don't race with it and I change the points every year or so. I keep a spare ignition kit in the trunk. It all fits in a small box.

A GM HEI won't fit because of the dual AC pulleys and a pertronix is no more reliable than P&C and when (not if) the pertronix goes bad, you're done unless you have the replacement parts in the car with you. The points will let you know when they are getting worn, and you can even file them clean once or twice.

Cadillac rear brakes have auto adjusters and 68 came with front discs (as an option, standard in 1969).

I have about 181,000 on the 68. All Original cast iron (overhauled), except the water pump.

Yes the HEI was great and the later distributorless ignition was even better. the mid 90s LT1 opti spark could have been great if it wasn't for its placement directly under the water pump, It is a good performing system as long as you don't get it wet.

But a good set of Delco points is still fine in the 1973 and older cars.
Where did I say Cadi Mikes 68 didn't have self adjusting brakes or 4 wheel drums?
Go back in time cars didn't always have self adjusting drums.
I can think of 1 even in late 1970's.
Many cars had 4 wheel drums into the early 1970's.
Even to this day many drum self adjusters don't work that great for the average driver.

But not long after cars had batteries they used points.
After WW2 Delco was already looing for a better replacement.
1963 GM began to offer electronic ignitions.

Didn't say the cars couldn't last 100's of thousands of miles.
Just that it was not the norm to keep them that long as it is today.
For engines they didn't last as long as more current designes.

Optispark could have been great. That sums it up.
GM dumped that idea years ago.
 

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Where did I say Cadi Mikes 68 didn't have self adjusting brakes or 4 wheel drums?
Go back in time cars didn't always have self adjusting drums.
I can think of 1 even in late 1970's.
Many cars had 4 wheel drums into the early 1970's.
Even to this day many drum self adjusters don't work that great for the average driver.

But not long after cars had batteries they used points.
After WW2 Delco was already looing for a better replacement.
1963 GM began to offer electronic ignitions.

Didn't say the cars couldn't last 100's of thousands of miles.
Just that it was not the norm to keep them that long as it is today.
For engines they didn't last as long as more current designes.

Optispark could have been great. That sums it up.
GM dumped that idea years ago.

I think you mean mechanical fuel injection in 1963, not electronic ignition which made its first appearance in some 1972 Chrysler models.

Yes, many cars used 4 wheel drums late into the 1970s and the auto adjusters were not all that great, but this is a Cadillac forum, whish (a least back then) had far greater materials and workmanship than most other makes.
 

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I think you mean mechanical fuel injection in 1963, not electronic ignition which made its first appearance in some 1972 Chrysler models.
For GM production vehicles the first electronic ignition was 1963 full sized Pontiacs with option code K66.
1964 Chevy added the K66 option to intermediate, full size, and Corvette with L88 or ZL1 engines.


1963 Lucas Transister Ignition Article
GM 1963 Production Electronic Ignition
1964-1965 Corvette Transister Ignition Wiring Diagram
1967 Delco Electronic Ignition NOS for sale
12/1963 Delco Bulletin - Electronic Ignition Conversion Kit

One problem was early units were subseptable to water damage.
Perhaps the transister quality wasn't as good as years later.
Or maybe the early componants ran hotter & were more prone to overheating.
Starting out as only an option on performance engine models that seem rare.
There may have been a time when replacement parts were hard to be found or too costly vs some aftermarket or newer factory option. Many of these got junked. They say the same of the early Corvette mechanical fuel injections.
Remeber even around 1990 a turbo Buick about 10-12 years old. The module was special to that year model was not available from GM or aftermarket. It was an extra box on the fan shroud that had a knock sensor. Had to trash it.
Point is not much of this stuff survived.


Wiki:
The first electronic ignition (a cold cathode type) was tested in 1948 by Delco-Remy,[3] while Lucas introduced a transistorized ignition in 1955, which was used on BRM and Coventry Climax Formula Oneengines in 1962.[3] The aftermarket began offering EI that year, with both the AutoLite Electric Transistor 201 and Tung-Sol EI-4 (thyratron capacitive discharge) being available.[4] Pontiac became the first automaker to offer an optional EI, the breakerless magnetic pulse-triggered Delcotronic, on some 1963 models; it was also available on some Corvettes.[4] The first commercially available all solid-state (SCR) capacitive discharge ignition was manufactured by Hyland Electronics in Canada also in 1963. Ford fitted a Lucas system on the Lotus 25s entered at Indianapolis the next year, ran a fleet test in 1964, and began offering optional EI on some models in 1965.[4] Beginning in 1958, Earl W. Meyer at Chrysler worked on EI, continuing until 1961 and resulting in use of EI on the company's NASCAR hemis in 1963 and 1964.[4]

Prest-O-Lite's CD-65, which relied on capacitance discharge (CD), appeared in 1965, and had "an unprecedented 50,000 mile warranty."[4] (This differs from the non-CD Prest-O-Lite system introduced on AMC products in 1972, and made standard equipment for the 1975 model year.)[4] A similar CD unit was available from Delco in 1966,[3] which was optional on Oldsmobile, Pontiac, and GMC vehicles in the 1967 model year.[4] Also in 1967, Motorola debuted their breakerless CD system. The most famous aftermarket electronic ignition which debuted in 1965, was the Delta Mark 10 capacitive discharge ignition, which was sold assembled or as a kit.

The Fiat Dino was the first production car to come standard with EI in 1968, followed by the Jaguar XJ Series 1 in 1971, Chrysler (after a 1971 trial) in 1973 and by Ford and GM in 1975.

Chrysler introduced breakerless ignition in mid-1971 as an option for its 340 V8 and the 426 Street Hemi. For the 1972 model year, the system became standard on its high-performance engines.
 

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The K66 is still a mechanically controlled system. It and the Lucas and are not true Electronic Ignitions. They are certainly not HEI systems, and were only used for a few years in high engine RPM configurations to eliminate point bouncing. The Lucas system still used contacts. The others were very low volume special applications.

If any of this was really useful, it would have been installed on Cadillacs. Cadillac engines of the 60 and 70s did not operate at high enough RPMs to need the K66.

GM's HEI was the first truly electronic ignition, supprasing both Frod's and Chrysler's in fatures and performance. It was the definitive Electronic ignition, (copied by everyone) until the advent of distributorless multiple coil ignitions.
 

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Below is a link from a former 1960 - 1970's Delco Remy Labs worker site dedicated to the transition to electronic & performance ignitions. They post pics of many of the orignal prototypes, engering drawings, ads, & some applications where they systems were used.

They also felt the Delco Remy Capacitor Discharge Ignition System always was the ultimate ignition system for any special high performance engine (high compression, high RPM, solid lifter, big cam), because it eliminated the “loading up” of the engine from slow speed, around town driving.

"I had a 1969 Z/28 Camaro back in the day that had this type of engine in it. After driving around town for awhile, when you tried to rev it up it would misfire until you took it out on the highway and “blew it out” by going thru the gears aggressively. The CD ignition virtually eliminated the need for this because even with build up on the spark plugs, the ignition system blasted right thru it due to the fast rise and discharge time of the capacitor. Along with the specially designed ignition coil for this system, the discharge across the spark plug was so quick there was no time for ignition energy to be bled off thru spark plug deposits, causing a misfire."

The autoher goes on to say the demise of the early systems were due to lean emissions
"This is the system I ran on my 69 Z/28 Camaro with the high winding, solid lifter 302 engine, and just loved it! No points to deal with, and maximum ignition output whether you were trying to start at 10 below zero or running at 7000 RPM! The performance was unsurpassed by any other ignition system around at the time. These systems never really caught on in popularity, probably due to initial cost and a short life span due to the coming emissions laws that forced lean carburetor mixtures. Due to the fast rise time and short spark duration, these systems needed the normally richer fuel mixtures of the 60s to operate properly. I think by 1970 these systems were done. However they would make a resurgence in about 15 years as the ignition system used on several Indy cars in the mid-80s!"


Acording to the auther the Delco Remy CD Ignition System was manufactured for both contact controlled and magnetic pulse applications.
"I have only seen the contact controlled version as an add-on kit. I have never seen or heard of it as an option on a new vehicle."

History of Delcos Ignition Systems


Here's Pontiacs Unitized Ignition which is a shift in the direction twords the 1974 HEI with the ignition module on the distributor. Not the plug wires are molded into the cap. K65 option interduced late 1971 & replaced with HEI by mid 1974. The cap & plug wires are all 1 piece molded together. Replacement parts including cap only made by Delco were discontinued after warrentys ended. Forcing owners to toss the system for HEIs.
Pontiac K65 Ignition
 

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None of this crap is going to help the OP. He fixed his points and now he needs a gas tank. I'll bet an 80's Fleetwood tank could be made to fit.
 
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