Using a Dual point distributor... What is the benefit?

....it looks right.

And it's possible that it might run a bit better at higher rpm, since you can get a bit more dwell out of it than you can with single points.

 

My 2 cents. A dual point distributor can make a nice noise, almost musical in nature and fits in well with the sewing machine sound solid lifters make. So, it's more than performance it's rock and or roll!
-Dave

 

The 392 came standard with dual point , just to get more dwell, and so a better spark.
It was nice in the 50,s but I think that a simple MSD 6a box will give way better spark with a lot less h***le

 

Yeah I thought about getting a unilite for my little 260, with additional ballastor and power filter but add the additional cost for those parts and add a coil into the mix and the price rises up to almost $400 . So I figured if the dual points distributor performed just as well I don't mind setting my points and saving a little cash while I'm at it.

 

The dual point adds some rpm band to the engine from the stock distributor. Stock may be 5500 to 6000 and the dual point may offer 6000 to 8000. Advance may be closer tailered to performance that the stock as well. Got one ? Why not run it , make you feel better as well..

 

They also extend point life by spreading the wear between 2 sets of points. Chryslers came stock with dual point distributors in the fifties, possibly other makes used them as well. They had vacuum and centrifugal advance.

 

Most of the posters point out the increase in dwell improved spark and increase in rev range are all soundly based comments. I have been running a Mallory twin pointer on my midget which is an off road compe***ion car which I use for hillclimbing. Over the time I have been running it , the last two years, I have had to come to grips with the quirks and limits of the twin point distributor. I overhauled it to remove slop and wear at various locations internally, cleaned up the points and fitted new condenser. I decided to upgrade the coil to a modern high performance coil. Seemed to me to be a sensible idea. I fitted a MSD2 Blaster coil which looks like a standard canister coil that have been with us for decades.This is a low resistance coil (.6 ohms). The manufacturer of the coil advises that you need to run a ballast resistor with it on a points type distributor. Plugs were set at 0.040" gap. Despite this I found that after each meeting the performance started to drop off. Each meeting involved 7-8 runs up a fixed course of about 800 yards and a return road of similar length. To my surprise the points were deteriorating (burning) and needed cleaning and resetting. No problem except that this all gets very time consuming. After tiring of all of that I fitted a Pertronix II conversion to dispense with the points. This permitted the use of the coil without the ballast and allows the maximum potential of the coil to be realised. I opened the plug gap up to .050" and as soon as I started it, (it fired on first hit of the starter ****on) it ran so much sharper and smoother than before. Whilst this is a track car all of this translates to the street. My essential point is that whilst those old twin pointers functioned well in their day, with all of the modern electronics there are greater efficiencies and performance to be gained. Despite being a fan of the traditional points and condenser for years you can do better these days and the beauty of these conversions you can't really see anything different.

 

In the '60s I ran a Rochester injected 301 SBC and out of necessity I had to use the dual point distributor to run the injection pump. Setting the points drill went like this: adjust the rough point gap to .016" and place a small piece of plastic shim stock between the other set of points. Fire it up warm and set the timing and dwell to 30#. Now shift the shim stock to the other set of points and repeat. Now remove the shim stock and check timing and check dwell.
I heard of a guy that just put the second shim in place then followed his wife's order to get it here now and eat Supper and when he came back to finish up it took over an hour to figure out why there was no spark.

 

I don't think there is any advantage to a dual point distributor. Those days are long p***ed.
The dual point was a big deal when 6 volts was the norm, allowing higher rpm when used as a dual coil, dual point device.
Electronics are the norm now with great reliability and rpm potential

 

Appreciate everyone's advice and input. I guess I'm just looking to make small upgrades that won't cost me too much and improve performance with the 260. I'm don't think Mallory offers a single point distributor for the sbf.
Also looking to eventually run a smaller carb, seems that the 600 CFM is just a tad too large but that's another story.

 

The 355 SBC in my avatar ran fine w/a Mallory up to ~6500 at 1/4 mile runs.

 

Haven't used points since high school. Most the guys I remember that had dual points back then, probably didn't set em up right or didn't need them anyway ( shifting at 6000 or less). I ran a single point distributor. We throw in a set of new points, close the cap and start it up. Open the window (Chevy) install your Allen wrench, turn one way till misfire, back the other way till misfire, set it in the middle. Crack the throttle a couple times to see what it sounded like and then set timing. Again, these were motors that were pretty much out of their power band after 6000 rpm anyway.

 

Yeah...but still, you know those stinky newfangled transistors are in there...it would drive me nuts.

 

I ran a Mallory dual point in a 355 bowtie heads, comp 292 magnum cam, tuned it weekly, ran well. Switched to a unilite and picked up 2 tenths the next weekend. Maybe I'm not the best dual point tuner in the world, but it made me a believer, and I wasn't screwing with it all the time.
Traded the distributor for an intake and never looked back.
Pertronics came out a few years later, swapped them into the 2 vehicles in the family that had points.

 

Well I called Summit yesterday to gather some details after learning on the web that the dual point/unilite was listed as unavailable. Doesn't sound good gentleman, currently they are not sure if MSD has any plans on re-stocking them with additional dual point unilites. For now looks like my only option would be to go the other route, wih the additional ballast and ignition filter.

 

You may be over thinking the issue.
Ford used to publish a Ford Parts Muscle book and manual that list performance improvements in stages like stage 1, 2,3 etc.
Stage one was a major ignition tune up and distributor curve , usually added like 10-12 hp. Good quality parts ( heavy duty) proper spark plugs , timing set and distributor curved for the application.
Dual point was after a camshaft change etc.
I would suggest finding a vintage Mallory dual point ( can be made electronic) rebuilding it and adding solid core wires etc. Performance is great and cant beat the look......
My friend Jerry held the National Record in J stock with a ford fairlane and 260 ci engine for years with a factory ford distributor..........

 

Deal ??

http://www.ebay.com/itm/Mallory-Uni...tem-/231532326906?hash=item35e866effa&vxp=mtr

 

If your points are burning you need a different condenser. Either the old one is shot, or if it is a modified ignition, you need one sized for your coil.

 

Rusty,
Points are fine, no excessive wear. Just wanting to add a little pep to the 260 and improve some throttle response.Plans for a bettter ignition system and smaller carb (500 cfm) for now.
Regards,
Mark

 

Bubba,
Thanks for the advice and tip on ebay. Thats what I am basically trying to achieve a little better spark and timing.With eventually better throttle response with a smaller carb.
-Mark

 

I was referring to fredeuce's post above.

 

Oh, I didn't realize.
Thanks

 

What it boils down to they just look kool

 

As stated in my post I fitted a new condenser. To up the capacitance to remedy the problem was certainly an option however that would have entailed some trial and error experimentation.
Knowing that the coil was best suited to an electronic/pointless system to extract its full potential , I figured it was time to change up and I have to say I am glad I did.

 

If your single point distributor is in good shape, no slop etc, just swap a Pertronics into it

Or send it to Bubba and he'll dial it in for you.

Only reason I went to a unilite was clearance and it was before pertronix.

 

Resurrection of a Zombie thread.
It is my understanding dual points wired together increase the coil saturation time and split by half the burning from switching the high amp load. Would agree with most that modern electronic ignition usually spark better and provides less labor opportunities. However from my experience with Chrysler factory electronic ignitions, you should always carry a spare control box and ballast resistor. While the pickup in the distributor rarely goes bad, if it does, you are stuck on the side of the road with hands in your pockets awaiting the tow. That is one thing that puts me off aftermarket triggered replacements like listed. Picture yourself in Resume Speed, SD on a Sunday afternoon.
Have a single point Delco ignition in 153cid Chevy II engine triggering a cheap antique Capacitive Discharge box. Most of the benefits of modern ignition with the fallback failsafe of swapping some wires and driving home on just the old fashioned point style. Delta Mark 10 was good enough for Baldwin-Motion, is good enough for me. On upcoming V8 project, plan to wire each set of dual points to separate CD boxes. As mentioned earlier, one set will open slightly before the other, so can switch between for advanced or retard with N2O. Either will be redundant and get you home, all for less money than a modern replacement.

 

Ken,
I note you mention dwell is the time points stay open in you question… you are looking at this wrong, you have to think in terms of 1 rotation of distributor and can fit every two crankshaft rotations on a v8…. And the term dwell is expressed in degrees, one rotation being 360 degrees and dwell is actually the time the points remain closed expressed in degrees so a dwell of .30 degrees would say points are closed 30x8 or 240 degrees leaving 120 degrees/8 or points open for 15 degrees firing 8 times. Dual points are wired usually in parallel and as mentioned offset on the advance plate one opens before the other and the second closes before the other. Hope that helps

 

Some more detail for the revived thread is that (if I remember correctly) Ford spec'd 35 degrees total dwell rather than the standard 30 degrees for single points. Many moons ago I isolated and tested each point set, getting 23 degrees on each set with the overlap making it 35 degrees total dwell. Reduced dwell meant less chance of point bounce and higher RPMs before hitting it.

I used to set up Ford duals for marine and street use. I even have the Blue Streak/Standard points part number burnt into my brain: FD8285XV...lol! I still run a dual on my 351W but it's a modified Accel triggering a MSD6T. The points are for backup if the MSD fails while traveling. Happened once and bacon was saved about 150 miles from home.

 

As I have pointed out in other similar threads, there are several variations of dual points. The one most discussed here (the points wired together in series) to increase dwell is the most common kind. I am most familiar with Mallory, and they at least, offered another version. This was the type where the distributor cam has only half as many lobes as is usual (an eight cylinder distributor with a four lobe cam). The situation is further complicated by the fact that this setup can be used in three different ways.

The first is to wire the points together and connect them to the proper coil primary terminal. When set up like this, each set of points energizes the coil 4 times per revolution, with every other impulse from each set of points being "wasted". The advantage of this is that each set of points opens half as often and less aggressive springs and cam profiles can be used, which can also serve to increase dwell. The second way is to wire the points separately, but connect them to the same coil primary connection. This works similarly to the previous example, but each set of points fires only when needed which extends point life. It has the disadvantage of being harder to set up. The third type is a distributor with a reduced lobe cam and two coil primary coil terminals. These distributors were designed to use a special Mallory coil with two primary terminals, but only one secondary terminal. This functions like a "poor man's" dual coil with the points in the distributor alternately energizing the separate primary windings, which then energize the single secondary winding. While not as effective as a "real" dual coil, but has the advantage of being able to utilize a standard single coil terminal cap and rotor. (There are a lot of guys out there with real spiffy dual coil distributors for which caps and rotors can no longer be found who can attest to this.)

I post this since there are a lot of used Mallory components coming on the market that cannot be used in the "extended dwell" mode, which can be confusing. Here are a couple of pictures. The first is an Olds Rocket with one of the special "two terminal" distributors' notice the two condenser which are required as this unit has two separate primary circuits. The second is a special Mallory coil with three primary terminals.

 

I believe the original intent was to get a hotter spark because of the longer dwell that could be had with 2 sets of points. 50 years ago I had a Mr. Gasket dual point distributor with mechanical advance only. I used to pull the distributor to set the points, put it back in an adjust the timing. The Mr. Gasket distributor had tighter tolerances and what not that was supposed to support a higher RPM. Must have worked because the SBC 350 I had it in would rev pretty darn high. The engine also had a Duntov 30/30 cam, good valve springs, Holley 3310, Tarantula intake, port matched, headers, etc. Personally I loved that setup. I'd run it today. I've always been able to get a points/condenser set up to run and get me home. But I try to carry an extra set of points and condenser around in the glove box.....That said BITD it was easy to get a set of points and a condenser.