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  1. #1
    Join Date
    May 2008
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    RV8 Mallory dual point "adjustment"

    I have a 4.6RV8 with what I think is an SD1 front cover (dodgy memory, I'm sure I was told when I bought it).
    While double checking the timing, I noticed I'm getting too much total advance. I know this is adjustable on the Mallory dual points, but I failed to work out how to get the top plate out of the distributor so I can get at the adjustment screws. Has anyone got any tips? I've searched around the net, but haven't found any conclusive drawings or guides...

    I have an ignition amp fed by one of the points in the distributor, but I am toying with swapping to a Pertronix or Mallory magnetic switch. Is it worth is and is one better than the other? I've found plenty about Pertronix on the net, but not much about the Mallory. I guess I can and would be better off keeping the ignition amp with one of these, is that true?
    Given the cost increase of an IgnitorII over and IgnitorI, I was struggling to understand what the benefit would be for the IgnitorII in real terms, has anyone any experience? From recollection I'm running and MSD Blaster3 coil and ballast, and I'm not in a hurry to spend more and replace the coil for the sake of it, as it's all running pretty well at the moment.

    Thanks, Richard
    --
    Richard
    GD Mk3 LS6

  2. #2
    Join Date
    Sep 2010
    Location
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    814
    My experience is with a Mallory Dual-Point in my FE, but perhaps at least some of what I can tell you may help.

    On my Mallory, the top plate (under the rotor button that holds the point sets) is secured by two screws (with nuts) that come in from the side of the distributor bowl. In fact, the bolts also hold the cap retaining clips to the distributor housing. It is easy to get the plate out, but a bit fiddly to tighten when re-installing the plate.


    I eventually switched over the basic Pertronix Ignitor. Best thing I ever did for the car. We tend to think of misfires as those times where it’s so bad the engine bogs for a second, but with points, there’s a lot more misfires going on that we really don’t notice. UNTIL, one installs a Pertronix and the difference during acceleration is noticeable. Very smooth. So it’s worth doing.

    Subsequent to my installing the Ignitor, Pertronix came out with the Ignitor II. I can’t remember the details, but it wasn’t very successful for some reason. Finally, they came out with the Ignitor III. The big difference between the basic Ignitor and the Ignitor II is the multiple spark output plus a built-in RPM limiter. The II also has mulit-spark output, however I think it’s limited to lower rpms. Higher up it switches to a single spark only. I think the III outputs multi-sparks all the way through the rpm range, however check the Pertronix website to be sure.

    I did have some Ignitor problems for a short time, but switching to the Pertronix recommended coil fixed that permanently. With a standard points coil, you get slightly less spark energy with the Ignitor. In most cases, this will not be a problem, however with high compression engines, it can be one. At any rate, check the Pertronix website to see about coils. I seem to think the basic Ignitor works with points coils, but you need the II or III to work with low-resistance primary coils, such as found in most electronic ignition systems.

    I have two Mallory distributors, and both have the same problem. The drive gear is not a tight fit to the shaft, so the 1/8” split pin bends back and forth and with fatigue, it eventually breaks. This failure can be even more premature when using a High Volume oil pump. I solved this by drilling out the pin hole with a number 22 drill bit and installing a 5/32” pin with another 3/32” pin nested inside it, and with the “splits” 180 degrees apart. I’ve probably got about 3000 miles on the engine since I did that, so hopefully it will never happen again.

    To change the total mechanical advance of the distributor, Mallory sells a calibrated tool to make the job easy, however, I don’t have one of these, so I use the following method:

    Let’s suppose I want the timing at idle to be 16 degBTDC and the max advance to be 38 degBTDC. The difference in crank shaft degrees is 22, or 11 degrees at the distributor.

    With the dist cap off, remove the rotor button and points plate. Re-install the rotor button. Take a firm piece of wire and wrap it around the rotor button with the end pointing out past the rotor button end. Make it long enough so the wire ends somewhere near the outside edge of the distributor housing.
     
     
    Hold the rotor button firmly back (no advance, …fully CW for mine) and using a fine tipped felt marker, make a mark on the distributor housing just under the wire pointer.

    Now move the rotor button for max advance (fully CCW for mine) and make another mark.
    These marks won’t be too far apart, so you can measure directly between them without worrying about the curvature. Record the distance apart they are.
    Divide this by the circumference of the dist housing (I always use the outer edge for measuring marks and diameter). You can calculate the circumference by measuring the diameter and multiplying by pi (3.14).

    And that’s your mechanical advance in degrees.

    To set the distributor for 11 degrees of mechanical advance (which is what we wanted when I started this example), remove the points plate and loosen two screws you’ll find underneath (I’m going by memory of a few years back, so sorry I can’t be more exact with my descriptions). Rotate the advance plate a bit and tighten the screws. Now repeat your advance measurements with a new mark until the new measurement is 11 degrees.

    Now for slight hiccup with all of that. My advance springs are a bit light. I’ve found that my engine cranks (no advance) at a5 degrees, idles at 20 degrees, and max’s out at 38 degrees, so I always have to add that 5 degrees on.

    In the 16 idle and 38 max advance example, this means the total I want is not 11 degrees, but 11 + 2.5 degrees. No big deal, but something to be aware of. Most distributor springs presupposed to be stiff enough they don’t advance until off-idle, so this offset shouldn’t be a factor.

    Hope some of this helps.
    John

    “A prudent person profits from personal experience, a wise one from the experience of others.”

  3. #3
    Join Date
    Apr 2004
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    If you swap go for the Pertronix as it is a really good system, I fitted one to my old engine and it ran without missing a beat. A couple of years ago we fitted one to my mates car and that has also given no problems.
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  4. #4
    Join Date
    Mar 2006
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    If it was my lump I'd do anything to avoid points even if they are only being used to switch an amp on and off.

    With regards to a 4.6 lump you want to be running around 28-32 degrees all in depending on what state of tune the engine is in. (CR, cam etc). 30 degrees would be safe for most 4.6 engines.

    If you are running an Eddy 500 carb you will have problems running the vac advance system if you also want to run a decent idle advance. (which then carries through the rev range until the all in RPM figure). My 4.6 runs A LOT of idle advance but I do have a quite clever system which allows less advance at the cranking RPM. (I run 20 degrees at idle).


    If you have a standard cam then I'd go for maybe 12 degrees at idle, 30 degrees at 2750-3000RPM with the vac system permanently disconnected. (Assuming an Eddy carb is fitted). If you have a warm cam fitted you could go for 14-16 degrees at idle and still aim for 30 degrees at 2750-3000RPM. (No vac system).


    I wrote the 'dizzy' stuff ages ago on the site below, its worth a read before you start messing about if nothing else just to make sure that your timing pointer is setup correctly. Most of the stuff is still relevant but I don't use the standard (but modified) system anymore. Sorry if I'm teaching you to suck eggs here!

    Useful Articles By Members - How To Build a Pilgrim Sumo
    I refuse to engage in a battle of wits with an unarmed opponent.


    Rules for buying 'Go Faster' parts:-

    If it's fast and cheap then it's not good.
    If it's cheap and good then it's not fast.
    If it's good and fast then it's not cheap!

  5. #5
    Join Date
    May 2008
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    Cambridge
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    Thanks for the advice. I had completely failed to spot the screws behind the distributor cap clips! At least I can get it apart now.

    I bought v8pete's mk2 sumo. It has an Eddy 500 carb, vacuum advance plugged, and a warm crane 900571 cam with advertised duration of 276/284. The max advance was out past 40 degrees, so really does need restricting! I did double check the TDC mark, and I believe it is pretty close, I think it's about 2 degrees advance, +/- 2 degrees as my TDC measuring wasn't going too great. I'll aim for 30 degrees at 3000rpm.

    The timing appeared to advance quite slowly to start as the RPM rises, then it advances quite quickly after that. What sort of advance curve should I be aiming for, linear? I'm a bit vauge about what the rpm is at the moment, but hopefully I'll have the rev counter working soon!

    The MSD laster3 coil I have has pretty similar specs to a pertronix flamethrowerII, so I'm hoping that will be fine. Will an ignition amp be a benefit with a pertronix module?
    From reading the pertronix specs the ignitor is meant to be used with a coil with at least a 1.5ohm resistance. The MSD blaster3 is 0.7ohm, so if I keep the ballast, then it should be fine. The ignitorII can be used with a coil down to 0.6ohm, so maybe that would be a better if more expensive choice, and maybe one that doesn't want the ignition amp. Still confused by the choices!

    Thanks, Richard
    --
    Richard
    GD Mk3 LS6

  6. #6
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    40 degrees is quite a lot for a 4.6, you may well be losing some power if the engine is way over advanced. I hope that your engine has not been detonating, it might not be even with loads of advance if the peak cylinder pressure never gets high enough.


    With regards to the advance curve you will be hard pushed to work it out using a timing light and rev counter. In order to get say a two stage curve you will have to use two different springs with one being slack at idle. Really you will be fine with a more or less linear curve that starts at say 1000 RPM then is all in at a max of 3000 RPM.

    Do you know what your idle timing is at the moment?

    I'm not sure that you can use a ballast resistor can be used to get the total resistance of it and the coil to be correct for your amp, especially if the coil is a 12v jobbie. If it is then the coil will not be getting a full charge between firing pulses.
    I refuse to engage in a battle of wits with an unarmed opponent.


    Rules for buying 'Go Faster' parts:-

    If it's fast and cheap then it's not good.
    If it's cheap and good then it's not fast.
    If it's good and fast then it's not cheap!

  7. #7
    Join Date
    May 2008
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    t felt like it was losing power at high rpm, so I haven't been all that far up in the rev range too often, so hopefully it's all ok.

    Advance at idle is somewhere around 14 degrees. As you say, it's pretty hard judging the advance curve with a timing lights and rev counter, it's just I felt it the advance came it fairly suddenly after a bit of a delay, then it was more linear. Some more careful measurement will make me happy. I have a couple of alternative springs, but I'm interested to see what is in there first.

    I know what you mean about the coil and ballast. I'll think about that a bit more. Judging from the instructions, it should be fine straight with the IgnitorII and no ballast.

    Thanks, Richard
    --
    Richard
    GD Mk3 LS6

  8. #8
    Join Date
    Sep 2012
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    75
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    Interesting thread this, for me. Having taken over a ten-year-old build, I have a 350 chevy (350 bhp at 5,000 rpm) with a twin contact-breaker distributor which I can't identify. I don't know how "authentic" this is supposed to be, but my view is that the internals aren't normally on view, and contact-breaker points were possibly the most unreliable parts of older engines. Once I've got the car through IVA and registration, I shall be in the market for a proper modern distributor. It sounds like Pertronics is the popular choice, but how do I decide which one ? I have to get Mike Huddart down to see my car at some point to certify the engine age and I will undoubtedly ask him, but I wouldn't mind gaining some knowledge for interest now.

    Thanks chaps,

    Brian Evans.

  9. #9
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
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    CHEVROLET 5.7L/350 Chevy small block Gen I Distributors - SummitRacing.com

    There you go Brian, I've had loads of stuff from Summit much of it also available in the UK from Mike H, or Real Steel or Repower.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
    DAX Mk4, 383 Chevy Stroker, Tremec. SOLD
    Contemporary CCX 3-4028, 445ci Big Block FORD FE,TKO 600, Old School IVA'd and SOLD
    Dax De Dion LS2 and T56 IVA'd June '17 SOLD
    1965 Ford Mustang 289 Convertible FOR SALE
    In build- Hawk 289 Sebring

  10. #10
    Join Date
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    Malvern, Worcestershire
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    Quote Originally Posted by kdavies3 View Post
    CHEVROLET 5.7L/350 Chevy small block Gen I Distributors - SummitRacing.com

    There you go Brian, I've had loads of stuff from Summit much of it also available in the UK from Mike H, or Real Steel or Repower.
    Thanks Kev. Good to see that some of these items are specifically for small block Chevies.

    Regards,

    Brian

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