# Mallory Dual Point Distributor - Disassembly



## PontiacJim (Dec 29, 2012)

Pic #1 & #2 - I went to the Ames Tri-Power Nationals at the Summit Raceway in Norwalk, OH. On my trip up from NC, I stopped at an antique store. I could not pass up the "man-cave" vacuum gauge for $2.00. Have not tried it yet, but guess it works. I was not looking to buy anything at Norwalk, but when I spotted this Mallory Dual Point distributor, it was one of those things that was the "hot ticket" to have on your car when I was younger. I simply mentioned to the vendor I was talking with "Is that a Mallory Dual Point?" He said "What'll you give me for it?" I jokingly said $5.00 as I did not need it. He said give me $10.00 and its yours. Well for $10.00, how could I refuse - it was another man-cave item, but I could also see it being used if it worked.

The Mallory "YC Double Life" unit (no vacuum advance) I got has the 4-lobe point cam versus the 8-lobe cam found on most points distributors. Each set of points has its own condensor and by design, each set of points fires 4 of the spark plugs. This distributor is supposed to use a specific Mallory coil which is essentially a dual coil set-up with each condensor connected to one side of the coil and 1 coil wire coming from it that goes into the distributor cap. The purpose of this is to produce more energy/spark from each firing of the points. The 4-lobe cam also allows higher RPM's - where an 8-lobe cam may be limited to opening & closing the points at 7,000 RPM's before bouncing, the 4-lobe cam allows the points to reach 10,000 RPM's or more. And, because each set of points only fires 4 of the plugs, you get twice the life out of the points versus the 8-lobe cam. To use the Mallory like an 8-lobe cam, you simply join the 2 sets of points together with a common wire, eliminate one of the condensors, and then use a standard coil.

Pic #3 & #4 - Shows the condensor hanging on the outside of the housing. Most distributors have the condensor attached inside the housing. There is a provision for oiling the distributor bushing that the distributor shaft sits in.

Pic #5 - #8 - The distributor cap is a 3-piece deal. 2 screws hold the assembly together if you need to pull it apart. In pic #8 you can see how the spark plug wires are fitted. The lower section of the cap has "spikes" and the ends of the spark plug wires are cut and then pushed onto these spikes. So the wires are fed through the top section of the cap, through the rubber seal in the middle, and then down onto the spikes. The rubber seal actually holds the wires in place when the 2 screws are tightened down to hold the 3-pieces together and compresses the rubber to grip the wires.


----------



## PontiacJim (Dec 29, 2012)

Pic #9 - Looking down at the top of the distributor with the cap removed. You can see each set of points and how each is wired to its own condensor. It takes a bit of pressure to push the points open as they have a strong spring to keep them closed so the points don't bounce off the cam at high RPM's. This can cause accelerated wear of the point's rubbing block that rides on the cam.

Pic #10 - With the rotor removed, this is what you see.

Pic #11 - A better view of the 4-lobe points cam. The top set of points is on the "flat" side of the cam causing the points to be closed. The lower set is on the "high" side of the cam lobe and would normally cause the points to open (.018" gap). You can see the longer and larger cam arc that keeps the points open as being much greater and less "peaky" than an 8-lobe cam. The longer flat section of the cam lobe (points closed) provides more dwell time (17 degrees per point or 34 derees of dwell total) for more coil saturation and provides a much "hotter" spark when the points open. A typical Pontiac single points distributor is .019" point gap and 30 degrees of dwell.

Pic #12 - #14 - This is how you adjust the point opening once the points have been screwed snuggly down into place - but not cinched tight. Get the rubbing block found on the points on the highest part of the cam lobe. Looking at the point set on the left, the top screw that holds the points to the plate goes through a non-slotted hole and pivots off of it. The bottom screw goes through a slotted hole made in the points, allowing movement back & forth. Pic #13 is a closer view. That small triangle found in the points plate is used to position your flat bladed screwdriver into and twist off of. The flat blade is fitted into the small notch found in the points, and with the points hold-down screws just snugged down, but not tight, you can twist the screwdriver blade one way or the other to open/close the point gap as measured with a feeler gauge. Pic #14 shows the flat blade of the screwdriver in position. Then you twist the blade to open/close the point gap while slipping a feeler gauge between the open points. Most single points will have a gap of .019", so once you can slide the feeler gauge between the points with a little drag, you can then tighten the 2 screws that hold the points to the points plate. To test the gap, I go 1 size larger on the feeler gauge, .020", and it should not be able to slip in easily. Then use 1 size smaller, .018" and it should slip in easily. If good, re-test with the .019" feeler gauge to make sure that tightening the 2 points screws did not close the point gap. A dwell meter can then be used to fine tune the dwell angle (which may open or close the point gap slightly) to the factory or recommended specs with the engine running.

Pic #15 - With the points and the plastic bushings for the condensors removed, this is the points plate. The plastic bushings are what holds the points plate into position.

Pic #16 - Lifting the points plate up and off reveals what lies underneath - another plate. You can see the slots that the weight pins can slide within. You could shorten the slots, however if you choose to do this, and it would limit the weights movement - and your total mechanical advance. You can see the 2 round holes and through these you can see "tabs" which the weight springs are hooked to. The instructions say you can stick a tool through these holes and bend the tabs to increase or decrease the weight spring tension to fine tune the weights advance curve.


----------



## PontiacJim (Dec 29, 2012)

Pic #17 - Going to the base of the distributor, the gear has to be removed in order to further disassemble the main shaft and related parts. Not too tough of a job, just knock out the roll pin, and I used the wedge of a chisel fitted between the gear and housing and tapped on the chisel allowing the wedge to separate the gear from the shaft. You can now see how it fits together. Mallory recommends no more than .010" clearance/play between the gear and housing and you can see the steel and copper shim.

Pic #18 - Once the gear is off, you can now pull the main shaft from the housing.

Pic #19 - Close-up view of the top and bottom plates (sandwich) and assorted parts attached to the main shaft.

Pic #20 - Looking at the underside of the bottom main shaft plate. I have not figured out the purpose of the small spring in the lower right attached to the pin of the main shaft's "ear." The hole in the plate has a slight elongation and allows the pin/plate assembly to move about 1/16".

Pic #21 - Looking at the top plate from above. Very easy to disassemble by simply removing the snap ring from the pin. The cam lobe remains with the plate when lifted off. The cam lobe has its own hold down clamp, but is also a press fit. This allows the cam to be replaced if it wears out or if the timing/firing needs to be corrected through "rotor phasing." Rotor Phasing is more of a requirement for electronic ignition system which are triggered from a reluctor sensor on the distributor shaft, or from an engine management system which is being triggered off a crank and/or cam sensor. So don't get too worried that you may need to do this with your stock or aftermarket distributor. But if your ignition system checks out and you are still having mis-firing, a cough, a bang, or a backfire and the engine won’t run and you are out of options, check rotor phasing.

Pic #22 - C-clip removed allows the top plate to be lifted off. The 4-cam points lobe remains attached to the top plate.

Pic #23 - With the top plate lifted off, it exposes the weights/springs of the mechanical advance. You can now change out the springs, or even the weights, to dial in your mechanical advance. Appears to have 2 different springs installed for the advance weights.

Pic #24 - The weights/springs removed from the bottom plate. In the lower right you see a large flat headed pin/rivet. This is what secures the lower plate to the main shaft's "ears". This could be removed if the plate had to replaced or modified for some racing purpose or the main shaft replaced, but at this point, it is probably time for a new distributor or the job needs to be done by a professional.


----------



## PontiacJim (Dec 29, 2012)

Pic #25 - The hollow body of the distributor. You can see the bronze bushing that the main shaft slides down through and spins on. It can be replaced.

So there you have it. Always wanted to pull apart a distributor and see how it all goes together. Although this is a Mallory, some principals will also relate to the factory single point distributor should you decide to rebuild it.


----------



## 1968gto421 (Mar 28, 2014)

Thanks for the nostalgia trip Jim. I had one of those back in the '60's on my 394 Olds Rocket that I pulled from a low mileage '64 Olds Starfire to replace the terminally ill 371 in my '60 Olds Dynamic 88 2door hdtp. This was after I put an Isky E-2 cam in the 394. I loved the two piece distributor cap, so cool. It alone told guys I had a Mallory. After I got a Duster 340 4sp the Olds sat at my parents house near Piedmont. Dad had a junkyard haul it away and I can't remember if I saved the Mallory or not. That 394 was a torque monster like a Pontiac 428. (I wanted a '70 GTO but the Duster fit my budget better.) Ah, much better times than now.


----------



## Lemans guy (Oct 14, 2014)

Great write up and photos PJ, and as you noted dual, points allows more dwell time MSD therefore coil saturation at higher RPM. This would also prevent the point “Float” at higher RPM. Some GTO’s ran them.

But soon came HEI distributors and they didn’t have those same issues, so the dual points distributors were no longer produced.


----------



## Lemans guy (Oct 14, 2014)

MSD is a typo sorry..


----------

