It's been a while since I set my point gap, but in need of a tune-up.
Running a stock C5AE-12127-E distributor on my 67 GT500.
My points were at .012" and dual dwell was at 34 degrees. For the 67 428, the manual says .019-.021 gap with a combined dwell of 22-24. If I gap them both to .019 my dwell is too low, but then a dwell of 22-24 seems low from other cars I've worked on.
I assume I set the primary to .019 and adjust the secondary, thought I think last time I set both equal by trial and error until the dwell was in range, but hoping someone can refresh my memory.
Quote from: Brandon on July 20, 2025, 10:45:55 PMIt's been a while since I set my point gap, but in need of a tune-up.
Running a stock C5AE-12127-E distributor on my 67 GT500.
My points were at .012" and dual dwell was at 34 degrees. For the 67 428, the manual says .019-.021 gap with a combined dwell of 22-24. If I gap them both to .019 my dwell is too low, but then a dwell of 22-24 seems low from other cars I've worked on.
I assume I set the primary to .019 and adjust the secondary, thought I think last time I set both equal by trial and error until the dwell was in range, but hoping someone can refresh my memory.
You can screw with the points forever in attempts to get those dwells. That is up to you?
I would tell you to set the points with a feeler gauge and leave them alone.
Some of these distributors I've seen are showing signs of wear that will throw off the point setting.
The points cam must ride very accurately on the distributor shaft to maintain a accurate points setting. If it is off .001" then the points will be off .002".
It may need to be knurled and reamed?
I just had a Boss 302 distributor here that had ,004" play which made it impossible to set the points accurately.
If the distributor shaft top bearing is worn it is not that hard to replace it yourself or send it out for rebuilding.
Also, often enough you have to fiddle with the gaps to get the swell right on.
I'm actually getting very consistent results for both gaps and dwell. My question is whether 22-24 combined is what others set (seems low), and others are setting both points at .019"-.021" and ending up with 22-24 dwell, as mine require the gaps to be less than .019" to end up in that range.
Or are you both suggesting I'm needing to go less than .019" to get to the 22-24 dwell range because my distributor shaft top bearing is worn?
Is the dwell number with both points active? I don't recall and I am away this week and don't have the manual. I know when I run a dual point on the Sun machine I have to isolate one set of points (piece of cardboard across the contacts works). And I agree to just set the gap as accurately as possible and don't worry too much about it. I would also say if you can push on the side of the shaft and see the point gap change, it needs a new bushing. If it is only a tiny bit, you might be okay but I would not close up the gap to get a better dwell reading. Or run a Pertronix which doesn't much care about a little shaft movement or dwell numbers.
Here's the 67 manual I have which specifically shows .019-.021" breaker gap for all models and 22-24 degrees combined for the 428.
(http://blackboxcentral.com/images/Shelby-Ignition-Crop.jpg)
22-24 is for transistorized dual point. conventional should be 30-33
Interesting. Any idea why it refers to 22-24 rather than 30-33 in the manual? The original was obviously not transistorized, and it doesn't make any reference to it. Where did you get 30-33 from?
Quote from: rockhouse66 on July 21, 2025, 07:42:00 PMI would also say if you can push on the side of the shaft and see the point gap change, it needs a new bushing.
If I push on the side of the shaft, I can see it move, and I can
feel a point gap change with .001" feelers, but can't
measure a change with them. Meaning the play at the points is less than .001".
I doubt that small movement would result in anything noticeable in the engine performance.
Quote from: Brandon on July 22, 2025, 06:25:13 PMInteresting. Any idea why it refers to 22-24 rather than 30-33 in the manual? The original was obviously not transistorized, and it doesn't make any reference to it. Where did you get 30-33 from?
The transistorized refers to the R code Galaxies which used same distributor
Where did I get 30-33 from? Working on Ford dual points since I was 13 ;D
Quote from: TLea on July 23, 2025, 08:23:12 AMQuote from: Brandon on July 22, 2025, 06:25:13 PMInteresting. Any idea why it refers to 22-24 rather than 30-33 in the manual? The original was obviously not transistorized, and it doesn't make any reference to it. Where did you get 30-33 from?
The transistorized refers to the R code Galaxies which used same distributor
Where did I get 30-33 from? Working on Ford dual points since I was 13 ;D
But this is a 1967 Shelby GT350/GT500 Owners Manual, which wasn't transistorized. I'm not challenging your assertion because 22-24 seemed low to me, but surprised they'd have this big of a misprint.
Hope this helps, page 60 of a 1967 Shelby GT350/500 Owners Manual...
I've "fixed" cars with badly worn upper distributor bushings by installing a Pertronix electronic ignition. They use a magnet to fire the sensor and are not very sensitive to the air gap moving around.
https://pertronixbrands.com/products/pertronix-1281-ignitor-ford-8-cyl
The answer to ALL your issues is called petronix.
It's all underneath the cap, no one will ever know.
Set it and forget it.
Make sure you get ALL matched components
Best of luck
How many people still run dual points on their shelbys? How many run petronix? #689 still runs points.
Quote from: hertzz350 on July 23, 2025, 12:09:20 PMHow many people still run dual points on their shelbys? How many run petronix? #689 still runs points.
Neither, I ran MSD with the small black distributor cap and black wires, painted the MSD coil black and the top of the coil off-yellow. Painted the box black and mounted it under the battery tray.
I have always set Ford dual point dwell as, 27 deg each, with 34 deg combined.
For an OEM "look" with much improvement, now use an All-In-One vacuum advance distributor. Summit, Jegs, and MSD all sell the same product.
Quote from: JD on July 23, 2025, 11:15:01 AMHope this helps, page 60 of a 1967 Shelby GT350/500 Owners Manual...
That's exactly why I started this thread. It says 22-24 degrees (428) (combined @ idle)(both).
Quote from: Brandon on July 23, 2025, 09:50:50 AMQuote from: TLea on July 23, 2025, 08:23:12 AMQuote from: Brandon on July 22, 2025, 06:25:13 PMInteresting. Any idea why it refers to 22-24 rather than 30-33 in the manual? The original was obviously not transistorized, and it doesn't make any reference to it. Where did you get 30-33 from?
The transistorized refers to the R code Galaxies which used same distributor
Where did I get 30-33 from? Working on Ford dual points since I was 13 ;D
But this is a 1967 Shelby GT350/GT500 Owners Manual, which wasn't transistorized. I'm not challenging your assertion because 22-24 seemed low to me, but surprised they'd have this big of a misprint.
Only thing I can think of other than being a misprint is thats individual point dwell not combined but then why don't they do the same for the 289 version? I'm not great at posting pics so I sent pic of 65 Ford shop manual specs to another member to post. It shows both the transistorized and conventional
Tim asked me to post this image and his comment...
"I'm not very good at posting pictures, but this should answer his questions. Since there's no factory service manual for a 67 GT500, you can refer to the 65 Ford, which uses the same distributor in the 427.
I don't know why it says 20 to 24 in the Shelby owners manual, maybe it's talking individual Point dwell and not combined"
Quote from: FL SAAC on July 23, 2025, 11:59:49 AMThe answer to ALL your issues is called petronix.
It's all underneath the cap, no one will ever know.
Set it and forget it.
Make sure you get ALL matched components
Forgot the AAA card for the tow truck :D
Quote from: J_Speegle on July 23, 2025, 02:53:07 PMQuote from: FL SAAC on July 23, 2025, 11:59:49 AMThe answer to ALL your issues is called petronix.
It's all underneath the cap, no one will ever know.
Set it and forget it.
Make sure you get ALL matched components
Forgot the AAA card for the tow truck :D
Why in heavens name would you say that?
We have run petronix in the same car, same unit for 25 years.
No issues what so ever.
It's a great product
Quote from: FL SAAC on July 23, 2025, 04:13:02 PMWhy in heavens name would you say that?
Just opposite experience on multiple cars. Its often suggested, if your mechanically incline, to have a set of points and parts with the car just in case you do run them. Will leave it at that since this thread has a different purpose and focus ::)
Quote from: J_Speegle on July 23, 2025, 04:26:36 PMWill leave it at that since this thread has a different purpose and focus ::)
Well on that note, since you're one of the concours experts Jeff, any idea why the original owners manual seems to have incorrect dwell values? :P
Quote from: J_Speegle on July 23, 2025, 04:26:36 PMQuote from: FL SAAC on July 23, 2025, 04:13:02 PMWhy in heavens name would you say that?
Just opposite experience on multiple cars. Its often suggested, if your mechanically incline, to have a set of points and parts with the car just in case you do run them. Will leave it at that since this thread has a different purpose and focus ::)
Gotcha you have had bad luck.
We have carried a spare petronix in our trunk for years because of these rumors.
Never ever have had to use it on our multiple cars.
On another note we also carry a spare tire, again have never had to use it either.
Quote from: FL SAAC on July 23, 2025, 04:13:02 PMQuote from: J_Speegle on July 23, 2025, 02:53:07 PMQuote from: FL SAAC on July 23, 2025, 11:59:49 AMThe answer to ALL your issues is called petronix.
It's all underneath the cap, no one will ever know.
Set it and forget it.
Make sure you get ALL matched components
Forgot the AAA card for the tow truck :D
Why in heavens name would you say that?
We have run petronix in the same car, same unit for 25 years.
No issues what so ever.
It's a great product
Maybe because you are running a "petronix" and Jeff is talking about "Pertronix" 😄
Roy
[quote ]
Maybe because you are running a "petronix" and Jeff is talking about "Pertronix" 😄
Roy
[/quote]
Roy you "Rhodes Scholar" you....
I ask you..."Tomatoes or Tomatos"
Let's get back on topic on this dwelling question, does anyone really know the dual point dwell?
Alright, with my primary point gap at .017" and secondary at .015", I get a dwell of 31-32, which I'll call good. With them both at .017", I was just below 30. Not sure why the gap is so small to hit that dwell since Tim/JD confirmed the gaps should be .019" to .021".
6S1766 is running points.
Joe
Out of my continued curiosity, I ran across this thread:
https://www.saac.com/forum/index.php?topic=28836.0
So is the correct part C5AE (traditional) or C5AF (transistorized)? The thread I referenced above seems to indicate C5AF, and if it were that, the manual would be correct vis a vis Tim's comments on 22-24.
Just to circle back I just broke in 67 engine in run stand. Set each set of points @ .020 and dwell was right at 33
Interesting, I wonder why my gap is so much smaller to get to 33.
Hi to all,
As mentioned dwell is affected by a few factors, the first is distributor bushing clearance.If wear is excessive points are very erratic as engine speed changes.Second is rubbing block condition,which I suspect is what explains the numbers you are seeing.
Easy way to prove this would be try a different brand or compare with a set of OEM points.This is a great example of how engine management has progressed over the years
Now the crank triggered/camshaft monitored style is very precise regardless of miles
Or hours of use. Best way to see if your parts are still good is test with a syncrograph machine....something few people see anymore. Hope this helps R.R.
Yall still "dwelling" on this subject
One word
Pertronix
It was a simple question and the simple answer is that it just isn't that important that you have the maximum dwell.
All that is doing is giving the coil the maximum amount of time to build a charge at very high engine rpm.
The thing that you feel immediately with the Petronix is that the engine seems more powerful but that is simply more built in dwell at idle and seriously is difficult to measure on a dyno.
It might amount to a few ft-lbs of torque on the street.
The major benefit would be that the plugs, particularly the 32 series would run cleaner, longer but the negative is that you will be replacing them because you are burning through the tips faster, rather then replacing them because they are fouling.
The bottom line is that you are still replacing them, so with points the simplest, which often is the best for a different reason, is to just set the new points by gap and forget them.
Also consider that later CJ 428'x would probably run BF32's whereas the 67 GT500 runs BF42's. So speculating why you might consider the interaction of the dual points with more dwell and the tendency of the 67 with the automatic transmissions to foul spark plugs prematurely?
You should remember though that the points for the duel points run higher tension and wear out the rubbing blocks faster so the points are closing down sooner then the single point distributors are. That means servicing the points sooner then the 25,000 to 30,000 mile servicing of the single point distributor.
So if all of this is no doubt spinning your head? Well, "Mr.Andersen, welcome to the Matrix", the program is running and be aware of where the phone is located? ::)