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Thread: points vs pertronics

  1. #1
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    Default points vs pertronics

    Just want to get some opinions. I have a 79 345 auto. I thought that should have been a solid state Prestolite distributor but it has points. I found no markings on it but it is obviously the newest part of the motor. To get the correct points I brought the old ones to the auto store and according to them it is a Prestolite distributor. At least the points were correct. I was towing my camper this weekend in the hills in Bastrop, Texas and it just seems to lack power for such a torque-y motor. Do yall think it would be advantageous to switch to the Pertronix add on in the Prestolite distributor? I realize it could be any number of issues right down to a worn out tranny but it doesn't slip or anything. If I could completely rule out ignition ssues that would be good enough to me. Thanks guys.

  2. #2
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    If you are getting the rpms without misfire, the points and condensor are working well enough. The electronic ignition systems are only really beneficial for emissions. Even the high energy spark systems don't really add power. They do clean up the burn, though.

    Make sure your dwell is consistent all the way up to 4000 rpms. If so, the points are fine.

    When the vehicle is running, (+) voltage on the coil should be less than 10 volts, but more than 7.

    Timing should be 5 degrees BTDC plus 1 degree for every 1500 feet above sea level. You might be able to get away with more, but if it pings, it's advanced too far.

    Vacuum should be between 17 and 20 at 1000 rpm or higher. You can tell how well the engine is running with a vacuum gauge. I like having one on the dash.
    Allan E.
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  3. #3
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    Thanks for the good information Allen. My scout is at a shop right now getting new ac hoses fitted. I did add a ballast resistor so hopefully that's good but I will have to double check. Do I need a hundred dollar timing light or will most so the job correctly? I drove all over the place with no missing so perhaps dwell is fine I will check later to see if it changes while reving high. Oh yeah the points cap rotor and coil are new. Vacuum I have never checkedsurely could be an issue. Don't really know my way around the carb either so more room for improvement. Really hoping to find a timing issue. Would really be nice to have some power with all this gas I am buying ya know?
    Last edited by jtl1100; 07-21-2009 at 02:47 PM. Reason: Spelling

  4. #4
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    Quote Originally Posted by jtl1100 View Post
    Thanks for the good information Allen. My scout is at a shop right now getting new ac hoses fitted. I did add a ballast resistor so hopefully that's good but I will have to double check. Do I need a hundred dollar timing light or will most so the job correctly? I drove all over the place with no missing so perhaps dwell is fine I will check later to see if it changes while reving high. Oh yeah the points cap rotor and coil are new. Vacuum I have never checkedsurely could be an issue. Don't really know my way around the carb either so more room for improvement. Really hoping to find a timing issue. Would really be nice to have some power with all this gas I am buying ya know?
    A cheap timing light will work just fine. The key is brightness so you can see the flash. Nothing is more irritating than having the timing light work but not be able to see how the marks line up. White chalk, white paint, or white out on the marks help. Flourescent paint or glow paint is also a good way to make it more visible.

    The only thing different between the IH engine and most others that have a distributor is that it times off of the number 8 cylinder. No big deal. You're looking for the highest possible vacuum at idle for setting both idle mixture (set screws at base of carb) and timing, then retard it a few degrees. The vacuum advance should be disconnected and plugged on the carb side. Once that is set, it should be reading about 5-8 degrees at 650 rpm with the idle mix screws in just far enough so it doesn't die on you. Start with about two full turns from all the way in, then tighten 1/4 turn at a time, check vacuum and timing, repeat. If it starts to die from lack of gas, back it out a quarter turn and stop. Both adjustments are done together to tweak the idle timing.

    Once that's done, you unplug the hose and hook the vac advance back up. Idle should be the same once it's hooked back up. If not, your power valve is shot. If still the same as when line was plugged, you rev the engine. Timing will advance quite a bit.

    Then you drive it. If it pings (sounds like BBs in the engine) going up a steep hill at lower rpms, the timing is too far advanced. If not, you're good to go. If it only pings pulling the trailer or boat going up the hills, try higher octane fuel or retard the timing a little. I have one scout that ran great in the mountains, pinged in the desert, so I ran high octane fuel when I drove down to Phoenix. That got rid of the ping. At higher altitudes, I didn't need it, so the tuning was right for the higher altitude.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
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  5. #5
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    Default novice

    Quote Originally Posted by Allan E. View Post
    A cheap timing light will work just fine. The key is brightness so you can see the flash. Nothing is more irritating than having the timing light work but not be able to see how the marks line up. White chalk, white paint, or white out on the marks help. Flourescent paint or glow paint is also a good way to make it more visible.

    The only thing different between the IH engine and most others that have a distributor is that it times off of the number 8 cylinder. No big deal. You're looking for the highest possible vacuum at idle for setting both idle mixture (set screws at base of carb) and timing, then retard it a few degrees. The vacuum advance should be disconnected and plugged on the carb side. Once that is set, it should be reading about 5-8 degrees at 650 rpm with the idle mix screws in just far enough so it doesn't die on you. Start with about two full turns from all the way in, then tighten 1/4 turn at a time, check vacuum and timing, repeat. If it starts to die from lack of gas, back it out a quarter turn and stop. Both adjustments are done together to tweak the idle timing.

    Once that's done, you unplug the hose and hook the vac advance back up. Idle should be the same once it's hooked back up. If not, your power valve is shot. If still the same as when line was plugged, you rev the engine. Timing will advance quite a bit.

    Then you drive it. If it pings (sounds like BBs in the engine) going up a steep hill at lower rpms, the timing is too far advanced. If not, you're good to go. If it only pings pulling the trailer or boat going up the hills, try higher octane fuel or retard the timing a little. I have one scout that ran great in the mountains, pinged in the desert, so I ran high octane fuel when I drove down to Phoenix. That got rid of the ping. At higher altitudes, I didn't need it, so the tuning was right for the higher altitude.
    Ok so I don't have a tool for checking vacuum pressure, I have it set now with the vacuum hose pulled from the carb and plugged at about 8 btdc and idle at 800 with the ac off and 650 with it on. It doesn't seem very "wicky" but I suppose it shouldn't. Messing around with it a little when the degree was way out of whack like 20 btdc it was real responsive. I was tempted to leave it really far advanced but it may have just seemed more resposive because the farther advanced i went the higher the idle was so revving the motor while its at 1500 seems a little more quick to respond than when its at 650 reving. I am in Houston so we are at seal level, 99% humidity and 100 degrees F lately. Would there be any advantage to a higher number advance and reducing the idle with the screw?

    Thanks again, i am on the hunt now for a hand me down vacuum gauge.

  6. #6
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    Quote Originally Posted by jtl1100 View Post
    Ok so I don't have a tool for checking vacuum pressure, I have it set now with the vacuum hose pulled from the carb and plugged at about 8 btdc and idle at 800 with the ac off and 650 with it on. It doesn't seem very "wicky" but I suppose it shouldn't. Messing around with it a little when the degree was way out of whack like 20 btdc it was real responsive. I was tempted to leave it really far advanced but it may have just seemed more resposive because the farther advanced i went the higher the idle was so revving the motor while its at 1500 seems a little more quick to respond than when its at 650 reving. I am in Houston so we are at seal level, 99% humidity and 100 degrees F lately. Would there be any advantage to a higher number advance and reducing the idle with the screw?

    Thanks again, i am on the hunt now for a hand me down vacuum gauge.
    You can buy a cheap vacuum gauge at Harbor Freight in Houston for about 10 bucks last time I looked. Cheaper if you go to yard sales sometimes.

    At sea level, a 304 is good at about 5-8 degrees BTDC. I'd leave it that way.

    When everything is working right, there is less advance at idle, but when you hit the gas, the timing jumps up a few degrees, giving you better throttle response. That's called "ported" vacuum. It's a smog thing. If you run the vac advance off of manifold vacuum and idle it down after you time it, it will run better, but it won't pass smog testing.

    <side note>

    The vacuum advance is there to RETARD your timing under load. That is its only function. This protects the engine from pinging, knocking, whatever you want to call it, which causes damage, like holes in the piston and fun things like that.

    <end side note>

    If you have the timing too far advanced, you will get pre-ignition, or knocking/pinging. Higher octane fuel allows you to run more advance without ping. In an engine as old as this, that is the function of higher octane, slowing down the burn speed. The muscle cars of the 70s often used the high grade gas because the timing was advanced for more power. Yes, it will pick up much quicker with the timing advanced. As long as there is no ping (up a hill in high gear under load) you're okay. If it sounds like there are bb's in the engine, the timing is too far advanced. You retard it until it goes away. If you retard it until it "almost" goes away, and does go away with high octane fuel, try it for a few tanks. The increased fuel economy might be more than enough to offset the 20 cents a gallon extra fuel cost. At 2.50 a gallon, 25 cents a gallon is 10%. More than 10% fuel economy increase is a good deal at that point. I have a scout that runs that way, gets 14.5 mpg instead of 12.5, so I run the good stuff. The rest don't seem to be affected. Not curious enough to figure out why.
    Allan E.
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    Charter Member, Old Hippie IH Club
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  7. #7
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    AFAIK, only the 80 model year Scouts don't have points. We did however get a single exhaust and EGR equipment :-(
    6/16/2009 - Bought my 1980 Traveler (345A)!

  8. #8
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    Quote Originally Posted by Scorp1us View Post
    AFAIK, only the 80 model year Scouts don't have points. We did however get a single exhaust and EGR equipment :-(
    Electronic ignition started in IH in 75 with a Holley gold box. All 75 scouts, pickups, and travelalls had this ignition in 75 and 76. This was replaced with the prestolite in 77. It was all about smog. IH was buying time, so in 75 they added the gold box ignition to comply with smog laws, but they also upgraded the suspension so that the scout would be exempt. This was called the XLC, which was extra load capacity. They marketed it as beefier suspension, but it was nothing more than an end around the smog laws. By 77, they had decided that the prestolite was more reliable.

    74 and earlier have points. IH used Delco distributors with the window on the cap through 64, then a Holley, and later a prestolite points distributor. All of these units mechanically interchange.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

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