tips on setting points / dwell

Before everyone goes blasting me for keeping the cars original point style distributor, I will be changing it out for a more modern electronic ignition, however, I do not have the funds for that yet. This was my grand pops car who gave it me to keep in the family since I am into old cars. Its a 69 Roadrunner that he bought new. I got a new set of points from the auto parts store and I think its called a "uni-set" ? Its a points and condenser together. I got the car running and idling good, but is there a way to easily set the dwell for the car? At least I think its something to do with the dwell because when I floor the gas pedal, it starts to stumble a little at times. If you gradually floor the pedal, its fine till it gets higher in RPM's. Then it starts stumbling again. It did not do this before changing out the points. Can anyone give this young gun some pointers till I can afford an electronic style distributor?

Thanks in advance guys / gals.

We don't blast people here bro (at least not like it used to be!). Points are fine (I grew up with em). get the points open all the way up on the cam & set em to .017" with a clean feeler gauge then check timing. You might also clean the contact faces with a touch of brake kleen on a thin piece of rag. put a very light touch of grease on the fiber (its non metallic) block that contacts the cam to keep it from wearing excessively.

Nothing wrong with points, look how good it ran from 1969 till you changed something.

Do you have a dwell meter and a .017 feeler gauge?

You will need a dwell meter to set the dwell. It sounds like you don't have one so just remove the distributor cap, bump the starter until you see the points open up with the point rubbing block on the tip of one of the eight lobes. Use a feeler gauge and set the point gap to .017 -.018. Make sure the gap stays the same after you tighten the point lock screw.

I drove Mopars for 30 years and always set the points with a feeler gage. Bought a dwell meter when I bough my Pontiac. Never used a dwell meter on a Mopar. On the electronic ignition, I changed out a dual point distributor for a MSD distributor and a 6AL box, didn't see any difference in 1/4 mile time. So, if your point distributor is in good shape, no bushing ware, and the point are set correctly, save your money. To check for bushing ware you can check it with a dwell meter . If the dwell goes crazy when you rev the engine the shaft bushing is worn out.

I always set points a little looser than the book called for so that when the rubbing block wore a little the dwell would be right in the middle of the acceptable range. My first race car used a Mallory dual point in the 440 and it never failed me.

Ok, thanks for the tips. I do have a digital timing light made by Actron that my parents got me for my birthday and I can't wait to really start using it.

Just to clarify, I need to set the point gap first and THEN check the timing?

I know my fathers good friend has a Chevelle that the distributor has a little window that you can use an Allen wrench in there and adjust the points. I guess Mopars don't have that on the cap? Or do I just have a cheap distributor cap that doesn't have that little window thingy?

If you have an original RoadRunner it would have the distributor in the front of the engine on the passenger side. And no, the distributor does not have a window where you insert an allen key and adjust the points. That is common to GM distributors. Still it should be an easy job especially if you ask an old guy how it is done.

install the points. set the gap to .017". clean the contact faces. Lube the fiber piece. set the timing. all done. don't even need to borrow a dwell meter as it is just a way to confirm the gap is in the ballpark electronically on the scope and actually you have alot of leeway on what gap you can run but not to muddy the waters. .017 is perfectly fine. Holler if it runs OK as before. EDIT note what the timing is before you twist the housing as it did run OK at that timeing before if I'm reading this right

Yes. All I did was change out the points. I did not change the timing at all. It runs good idling and giving it slow throttle but when you stomp on it, its strong but then starts breaking up. Its almost like the points are bouncing causing the engine to "stutter".

Could be point bounce as you note. I'd recheck your gap measurement and if you have a dwell meter check it as well just to see where it is sitting. You might check the timing and dwell in park, run the rpm up and see what the timing does and the dwell at higher rpms. That should tell you something about dwell and timing stability - as it relates to bounce.

When checking timing , you must disconnect the vacuum hose from the distributor and plug it. Then check and set the timing to spec.

IF the point gap is set correctly, the dwell will be within specification. IF the dwell is set within specification, the point gap will be right. They are looking at the same thing, just describing it differently.

The GM setup was nice because most of their distributors were on the rear of the engine, so you hooked up a dwell meter and with the little flex hex tool you turned the screw until the dwell was correct.

Dwell is the number of degrees the points are closed, per cylinder. The only way it isn't connected to the point gap is if the distributor cam is worn quite a bit.
Unless you use a high tension set of points, the distributor cam is good for the life of the engine. So setting the points different than spec in case something might happen is IMHO wasted effort.

You can check the point gap after a year or so by using a dwell meter, then you don't have to fool around in the distributor.

You can see if you are getting spark by using your timing light's inductive pickup on every plug wire and seeing if the spark gets erratic as rpm increases. It's a quick and easy way to get a handle on whatever is causing the breakup.

I doubt very much that you are revving the engine high enough to get point bounce, that would generally start around 5000rpm. It's most likely something else, like a partially plugged fuel filter or improperly set float, or a power circuit in the carb which is activating when it shouldn't. Or a piece of dirt in a jet. Etc, Etc, Etc.

Just remember the first rule of auto mechanics: DO THE EASY STUFF FIRST! If you don't you will replicate my feat of having to buy a new carburetor main body to replace one I trashed, trying to fix a miss that was caused by a bad distributor ground!

R.

Ok, thanks. All good info that I will use tomorrow since I have off from my job.

Yes set the point gap (dwell) first then set the timing. Setting the points or replacing them and setting them will change the timing so you should always set the timing after changing or adjusting the points. The carb adjustment should always be the last thing you do after the timing. Ron

Awesome, thanks Ron. I did that and took the car for a spin today since I ran out of time yesterday. The car seems to pull better from a dead stop and I did not notice any of the stumbling, at least as bad. Maybe its cause the choke wasn't fully opened up yet?

did you increase or decrease the gap?

Keep in mind...
For setting the points, the factory specs are 0.016" to 0.021". But note that the rubbing block wears over time, decreasing the point gap. So I would recommend setting the points to 0.019" to 0.02" giving U some margin as the rubbing block wears.

Just my $0.02...

I increased the gap just a little bit. The little bit that I adjusted it I honestly did not think it would make a difference but it seems that these things need to be dead on otherwise you can get some performance issues.

That is exactly what I used to do, too But since all of our vehicles use electronic ignition in one form or another, my dwell meter has been collecting dust for at least 29 years.

FWIW I use the original points dist and an Old MSD 6A. The load IE current to the points is reduced and they are only used to trigger the box. They last along time and dont burn or pit. I also keep a harness and the ballast resistor in the trunk if the MSD fails. Never ever had a problem and was a swapmeet find. Did I say I am Cheep?

Take dist out and set in the box the electronic dist came in. Many hours wasted on that pos.

You need to remember that changing the point gap changes the ignition timing.