Mattia-SS

Does anyone know what´s the correct breaker point gap for my 70 Cutlass 455? I searched and found dwell angle and .019?? I have no clue at all what this means so keep the answer simple

Highwayman

.019 would be the point gap.

oldcutlass

It would be more accurate with a tach and dwell meter. Set it to 30. If you change your dwell or point gap you need to set your timing after.

Highwayman

You're right but the request was for point gap and to keep it simple. I kept it simple.

MDchanic

And, since Mattia is in Europe, to keep it even more simple, 0.019" = 0.48mm .

Setting the gap using the dwell angle is still better, though, especially if the points are not new, as used points cannot be set accurately using a feeler gauge.

- Eric

ah64pilot

I'll make it even simpler:

http://www.summitracing.com/parts/MSD-8529/

Take it to a shop and have them install it...Done, forever.

AZ455

Or these!

http://www.pertronix.com/prod/ig/ignitor2/default.aspx

&

http://www.pertronix.com/prod/ig/fla...5000_volt.aspx

Mattia-SS

That´s the kind of answer I like What´s a dwell angle??

rustyroger

Dwell angle (measured in degrees) is the period the points are closed while the the distributor is turning.

The coil needs time to build up sufficient charge to fire the plugs, this happens when the points are closed, when the points open is when the plugs spark.

Making the points gap smaller increases the time they are closed, but too small a gap makes them more likely to not open properly, too wide and the coil can't build up enough charge to make a good spark. That is one reason points ignition can't handle high rpms, the coil simply can't cope with the short time the points are closed, also at high speeds you get the phenomenon of points bounce (not closing properly during the dwell period).

Set the points gap to what the shop manual states then adjust them to get the correct dwell angle, then set the timing. Do it in that order, unless the distributor is worn or faulty in some way when the dwell angle is correct the points gap will be pretty close to the recommended gap.
Getting the dwell right is the first step to getting your engine tuned properly, if you don't get it right you won't get the rest right.

Electronic systems have different requirements, but that isn't relevant to this thread.

Roger.

MDchanic

... And, as points are used, they develop slight "hills" on one side, and a corresponding "pits" on the opposite side, so that if you insert a feeler gauge between the contacts of a used set of points, you are actually measuring between the tops of the "hill" and not the flat parts, which creates a reading that looks right, but is actually too wide.



Also, just to keep it "simple," here is a picture of what "dwell angle" means (this is on a six cylinder engine - an eight cylinder engine (in most cases) has an ideal dwell angle of 30° out of 45° of rotation, with points open for 15°).



- Eric

droldsmorland

A quick scan of all the posts no one mentioned it so I will. Clean the feeler gauge with brake or carb cleaner. And do the same with the points. Dirty points will pit quickly. Use a lint free disposable shop towel. Clean the breaker plate and the cam. Lube the cam with breaker cam grease. Clean and lube the weights and springs too. Make sure all the wire ends on the coil and condenser wire are clean and bright.
Do yourself and the car a favor and buy the highest quality point sent you can find. Ask the parts house if they can get premium points & condenser sets such as Blue Streak.

oldcutlass

I use a point file to clean up dirty points. I buy the points designated for a Corvette as the spring tension is much higher which makes for less point bounce at higher RPM's.

Highwayman

And more tension so the rubbing blocks will wear faster.

Do the Covette points have harder blocks?

brown7373

I used to use the high spring tension on my 69 Corvette, and they did work better at first, but would wear out in 3 to 4000 miles. As Highwayman said, the rubbing block wears out faster. My Vette had a factory 6000 redline, and with lighter points, I did get bounce as I approached 6000. But most Olds engines aren't designed to go that high. If you modify it to rev higher, chances are you would also modify the distributor to some electronic for best results.

Another problem that the high tension spring can cause is wearing out the rubbing block cam on the distributor. Once that loosens up, the distributor needs a total rebuild and replacement of that cam. Plus, many of today's points are Chinese or Mexican junk.

Mattia-SS

Left the car today at a friend to my dad, we´ll see how it goes. Btw the points are new. I though the brand was Streak something. Costed me 150SEK - 20$. I bet you pay 5$ for the same

oldcutlass

They are about $15 for a good set. The only points I ever had trouble with were the Mallory hi perf, those I would have to reset every 3 mos and replace every year. The vette points I would have to reset twice a year and get a few years out of those. It only takes about 5 mins to reset the dwell and timing, so it was never an issue.

I have a Mallory HEI on it now, my first venture into modern electronics on GM cars. I really don't see any real difference in performance over a dual point.

ah64pilot

On an engine that'll turn 6,000 RPM or more you'll notice. On the top end there is no comparison. And welcome to the modern electronics world I have MSD pro-billet distributors on both of my cars...set it and forget it. Cap and rotor change every...whenever I feel like it lol!

redoldsman

Nobody mentioned the simple method of using a matchbook cover. I never tried it but heard about it for years. Of course the problem now would be finding a matchbook. This was supposed to be an emergency measure.

Intragration

You can generally eyeball it and then adjust by feel in a pinch, matchbook or no. You need a tach/dwell meter to set dwell while the motor is running, this is the easiest way to get it just right. Can probably pick one up on E-bay for under $20. I love knowing that there are other anti-social guys such as myself who still run points. (not in my Olds, but my '70 Cadillac) Discounting the fact that they've never left me stranded, the amount of almost palpable hatred that some people have for them ensures that I will run them until I die.

rustyroger

I read in an old edition of car craft a discussion of the merits of points vs electronic ignition;
Points, cheap, simple as an anvil, cheap, no problem carrying a spare set and cheap.
Electronic, set and forget, good for high rpms, powerful spark for high performance engines.

I haven't come across any points haters, do passions about ignition systems really run that high?, better keep quiet about your carburretor or risk a lynch mobs fury!.

Roger.

droldsmorland

FYI Caution. Points have a thin film of tungsten plating or similar high end metals on the contacts for longevity. By using a "point file" you basically remove that protective arc coating. Filing is a short term fix and will get you by but the gap will go south very quickly. Thats why it’s important to start out with everything clean. The contamination will accelerate the tungsten degradation leading to pitting. In layman’s terms you get another 5-10K out of properly cleaned & gapped points. There’s even the argument that the feeler gauge will scratch the contact surface. Thats where the match book thing comes from. By using the match book which in the day was about .020" you could get the car started then use the Dwell meter thus not pre-damaging the points leading to premature failure...old racers trick. I try to not touch the contacts at all. Ill spray them with contact cleaner and blow em off with dry, oil free compresed air. I work on a lot of gensets that still run point ignitions in critical facilities that cant be down on utility power so I still see a lot of points.
This is why I now run with breakerless ignition when possible. Set it up and forget it.

oldcutlass

Points, by nature wear do to the arcing. They also wear on the guide strip. So you have to forces or nature working against you. The reason for the filing on pts is because as they wear with the arcing process the contacts tend not to close fully do to the mismatch in contact surfaces. The filing corrects that mismatch to a certail extent and eliminates misfires.

The matchbook was used mainly when stranded on the side of the road as a means to get the engine running well enough to get the car home due to not having the proper tools to fix it correctly there. Also the matchbook was used to insulate 1 set of points while adjusting the other on a dual point dist. It is a very usefull tool!

I still refresh my tune when the seasons change, and regap plugs once a year.

Intragration

There really are points haters out there, but in fairness, I don't know if I've run across any specifically on this site. It does seem pretty ridiculous to me too. I think it has to do more with lack of familiarity. They seem to think that points need to be adjusted every time you start the car up.