cokerintennessee

Car is 1970, 454 with Mallory Dual Point with Mech Tach drive. Having an issue with my Mallory Dual Point Mech Tach distributor. Only can get one of the points to spark. Switched contact wires thinking it might be a broken wire, but when those wire were switched the same point sparked. Replace points thinking had a bad point but same results. Have not changed out condenser. I hate to go to an electronic distributor especially with the mech tach. What suggestions does anyone have?

69427

Despite my complete disdain for anything Mallory or dual point, I'll bite. When you say one set of points "sparks", what do you mean? I'm familiar with how dual points work, but I want to make sure I'm following your vernacular.

7t9l82

call Mallory and get a unilite conversion. Mallory makes an excelllent product and the unilite will make maintenance easy. the condenser is likely bad.

cokerintennessee

There are two points in the distributor. When you crank the motor you can see only one of the points have a spark across the open point. Hope that explains it. Can't figure out why only one of the points sparks.

cokerintennessee

Thank you for your post. I will certainly check into that. Merry Christmas!

69427

For most of the dwell the points are in parallel. One set (closes and) starts the dwell, then the other set closes. Primary current is then flowing through both. At roughly 80-90% dwell time the first points set opens (while the second set is still closed). Because the first set doesn't interrupt the primary current there's no flyback voltage trying to cause a spark across the points. The second set of points interrupts the primary current (initiating the ignition at the plug). It's the second set that has the hard job. It has to carry more current than the first set, and it has to deal with the coil flyback voltage.

So, may I ask, is it the second set that's arcing?

cokerintennessee

Yes that is correct.

69427

Okay, now that we're on the same page, I would agree with 79L82 that you should check the condenser. It's the condenser's job to temporarily absorb the primary current when the second points set opens to prevent the flyback voltage from causing arcing of those points.

cokerintennessee

Perfect! Runs great.......now.

But I think I will do more research on the electronic conversion. I've only put 102 miles on the car in the last 3 years and this is the second issue I've had with the points.

Thanks again for all your help.