Thread: SBF stumbles. Ignition problem?

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My 67 mustang with 302 was running fine. I took it out today for a ride, and every now and then it would stumble a little at speed. It got progressively worse, and eventually started breaking up pretty bad, even stalling at a stop sign and hard to start again. Made it home, but didn't even want to idle in the garage.

Wires, plugs, cap, and rotor are all less than a year old.

The points did look pretty burnt up, so I replaced both sets (Mallory dual point). Checked dwell and timing. Started up and it's idleing good again. I think I've got it, so I take it for a spin. Not going hard on it, it seems to be running like a champ on my street. I pull out onto the main road no problem, but after I get going it starts to stumble again, not as bad as before, though. By the time I turn around and get home it barely idles again (but not stalling out like before). By now I'm so POed I parked it back in the garage and went back inside. I have to work tommorow so I won't have a chance to fool with it until tuesday, but I'd sure like to fix it on tuesday.

Any other ideas? My poor car

If the points burn quickly again check your coil as a original ford coil I think has a built in resistor and if you are using a aftermarket coil you might have to use a resistor like for a mopar to cut down the voltage to the coil. Jeff

The car is garage kept, and I had the air filter off when changing the points, even had it running without the filter in the garage, so that's not a problem. The carb was rebuilt about a year or two ago. I don't think it's a fuel problem. I had a similar problem last year but it was cured with wires. The points were just old and due for a change. I do have a mallory coil on there. Unless the HO coil is burning up plug wires, but they are good quality belden wires, with maybe 1,000 miles on them, so I doubt they are bad.

I'll check them out, maybe I'll have to upgrade to performance wires. All connections are tight.

Partially plugged fuel filter? At low speeds, especially after you've been sitting a while, the bowls fill fine. When you have higher demand for fuel, the filter won't let enough fuel through to fill the bowls fast enough. How old is the fuel in the tank?

Is your Mallory Dual Point an old unit? If so, you may want to get rid of it. You can update to a transistorized ignition if you so choose. MSD makes a "ready to run" distributor for the 302 ford that works great. All you have to do is install it, time the engine and never look at it again unless you pull the unit. I have a friend who bought one for his 302 in his 34 ford. Works great for him. Cost is moderate, about $300.00 but you will not have to change coils (it uses the stock coil) and you'll never have to set points again.

I like the points over electronic ignition. The mallory wasn't new when I got it, but it dosn't seem that old and it isn't worn out. (there is some up and down play in the shaft, but none left to right.) I also have a new mallory coil. The fuel filter is only 6 months old, and it was breaking up just cruising along at 50, not even hot rodding around.

Well, it seems that for every answer, I get 3 more questions.

I was out of ideas this morning and the car was still running poorly, so I swapped out the Mallory dual point for the stock unit. I dropped it in, set the timing, and went with it. It had fairly new points, condenser, cap, and rotor, so I didn’t even mess with it. I DID leave the Mallory coil on there.

I went out for lunch and the car is now running fine, although when I got home I had to bump the idle speed up, which was strange but seems to be the only side effect.

I guess I can’t complain, but I did several bench tests and I can’t figure out what’s actually wrong with the Mallory that was in there. I also see that the points are already showing wear, even though I put them in Sunday and ran the car for maybe 5 or 10 minutes and about 4 miles and the car was still running bad. I don’t really know if it’s normal to see slight wear on points after such short running, but I would think they would still look like new. Maybe the coil should have a resistor? I heard when I put it on the factory resistor wire would be good enough. Maybe I should use Mallory’s performance points, rather then their standard ones. But now I’m a little worried that the coil will burn up the single points in the stock distributor. Then I was thinking maybe the coil isn’t the problem, but maybe Mallory’s condenser (year old) is bad? But that is unlikely. Or maybe it’s just normal for the points to wear a little and I never noticed. They are obviously not worn enough to cause the poor running condition. So the actual problem hasn’t been isolated yet. I can’t find any short in it or anything.

Whew, I’m done for the day!

Your condensor is designed to absord the current when the points first open and prevent arcing (or burning of points). If you are experimenting with different distributors and coils, then perhaps you should contact Mallory (a tech line if they have one), tell them what you are running (coil/distributor combo) and see what they have to say.

If the condensor is a year old, then I'd definately swap that out. And run it for a while and see if the points still burn. Some metal transfer on the points is probably going to happen regardless.

Bob's point about fuel is good. Some of the fuel today is very crappy and if a station's tanks are dirty you can certainly get that in your car. Check out your fuel pressure and get a clear fuel filter up in the engine compartment. You can also get some fuel additive to run through your system.

The stumbling and point burning may or may not be related. Its possible that you have two different things going on at the same time.

Well, the condenser is almost a year old, but there's only maybe 1500 miles on the car sense then. I guess I'll change it anyway, but it seems strange that it would need a condenser already. It was a brand new mallory condenser too, not just some auto parts store replacement. Ofcorse, it wouldn't be the first time I've gotten a new part that was bad, didn't work, or didn't last.

Good tips on fuel, but I know this problem isn't fuel related.

I don't know if I'd consider that point burning, just seemed odd that I saw wear in one of the sets already.

Today I got all new stainless steel screws and washers, and I took the mallory all apart. I can't find anything wrong with it, and I'm pretty good with these things. I can only think that maybe the nylon insulator going into the housing isn't insulating properly, but I looked at both halves with a magnifying glass and only found a small line in one, which is probably from the way it was made, not a crack. I replaced it anyway with one from an extra dist. but I didn't put it back in the car yet.

Well, I put new points and condenser along with new stainelss screws in the mallory and put it back in the car. It's running fine now, but I never actually found the problem.

Is there any way to test a condenser so I can see if the old one was bad, perhaps explaining the problem. I had a simmilar problem last year and I cleaned the points and put in a new condenser. I hate to have to redo my distributor yearly with how little I drive the car. Thanks.

I think what junkyardjeff was refering to was a resistor on the primary portion of the ignition system also commonly refered to as the balast resistor. If the current running through your primary system is to hot (not spark plug or coil wires), then you could be burning points.

I don't remember exactly how Ford did their resistor, if it was built into the original wiring harness, the coil (as jeff has suggested) or if its a stand alone resistor. I can try to look it up. If the newer distributor does not have a resistor after the coil, then the current running through the points might be hotter than originally designed and thus burning the points.

The car has a resistor wire built into the dash. I havn't touched this. I hooked up the mallory coil the same way the stock one hooked in, same with the distributor, the wire just goes to the coil negative. I did have to put a tach filter on so I'd get good readings.

Supposidly the factory resistor wire is enough.

I think that there are many different options that are upgrades to having point(s) in your distributor. A Pertonix upgrade, MSD, later model Ford systems and even a Chevy distributor will hook up in a 289.

Check out this link for several different opinions on the subject:

http://www.corral.net/forums/showthr...ight=Pertronix

I don't really want electronic.

ok i know you wont like to hear this, but mallory is a company you should steer clear of, I've tried 5 different mallory's and they always end up having problems quickly and have even left me stranded in the middle of nowhere a few times. These problems have also happened to many of my friends.... besides burning up really quick, they also tend to have a problem with the gear not always connecting into the cam gear all the time, which would definately cause this stumbling problem you speak of. If i were you, i would try and get my money back or at least a few bucks... and upgrade your stock distributor with a protronics ignitor... they cost about $120, replaces the plate and turns your standard distributor into an electronic. i know you dont want electronic, but its really the only way to go without having problems with points and timing