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Old 03-25-2019, 03:08 AM   #1
mbiver
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Default Change 1977 345 to Prestolite points distributor?

I have a 1978 Scout II with a 1977 345 engine (original 304 blew and was replaced with 345). I have a Prestolite distributor with a Petronix electronic ignition in it right now and would like to change to a points style distributor. Iím not sure if thatís stock or if it was added by the previous owner. I thought I had read in another thread that they stopped using points style distributors in 1974. If not, and the previous owner added the Petronix, can I buy the parts and change it back to points? Or can I just buy a new Prestolite points style and swap it out? Just not sure what is compatible. Thanks for any assistance!
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1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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Old 03-25-2019, 05:43 AM   #2
Winchested
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Default Re: Change 1977 345 to Prestolite points distributor?

The later prestolites were an all electronic hall effect pick up, they were never points.
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Old 03-25-2019, 05:56 AM   #3
mbiver
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Default Re: Change 1977 345 to Prestolite points distributor?

Thanks, Winchested. If I wanted to put a points style distributor in, do you know which models would be compatible with the 345?
__________________
1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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Old 03-25-2019, 06:05 AM   #4
Winchested
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Default Re: Change 1977 345 to Prestolite points distributor?

Don't understand why you would the prestolites are world's better than the points style ever were.

If you went back to a points style you'd have to change out the coil and put in a condesor as well that matches the dist.
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Old 03-25-2019, 05:04 PM   #5
mbiver
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Default Re: Change 1977 345 to Prestolite points distributor?

Thanks again. I called in and chatted with the team from IHPartsAmerica. Very helpful! After discussing, I went ahead and ordered up a used Holley points distributor, points style coil, condenser, rotor, premium cap, points, vacuum advance, and wires from the IHPartsAmerica store. Sounds like the Holley should be compatible with my 345. Just need to put it all together.
__________________
1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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Old 03-25-2019, 06:55 PM   #6
Scoutboy74
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Default Re: Change 1977 345 to Prestolite points distributor?

Yes it should. Just curious as well about the why? Was something not working with your present setup?
__________________
Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - 392/TF727/4.10 RA17/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"
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Old 03-30-2019, 10:10 PM   #7
mbiver
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Default Re: Change 1977 345 to Prestolite points distributor?

Thanks for confirming compatibility, Scoutboy74. My Prestolite with electronic ignition is working just ok. Honestly, though, I want a working points style setup on hand so the Scout can be my EMP bug out vehicle. :-) I just got the "new" Holley from Jeff and team at IHPartsAmerica and have attached pictures. Needed a little cleaning, but so far so good. I did have a question about the condenser. Does it have to be inside the distributor? It's a really tight fit in there. I've seen them mounted to the side of the coil and was wondering if pulling it out and placing on the coil has the same effect?
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__________________
1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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Old 03-31-2019, 06:35 AM   #8
Scoutboy74
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Default Re: Change 1977 345 to Prestolite points distributor?

Yes, the condenser for the points always mounts inside the distributor. The item you've seen attached to some coils is a noise suppression capacitor meant to eliminate the interference heard through the MyT Fyne, AM sound system while the engine is running. Not as essential these days with quality insulated spark plug wires.

Do you know about the resistance requirements for protecting the points and coil?
__________________
Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - 392/TF727/4.10 RA17/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"
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Old 03-31-2019, 12:09 PM   #9
mbiver
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Default Re: Change 1977 345 to Prestolite points distributor?

This is the first distributor Iíve ever set up so I definitely donít know about resistance for the points and coil. Iíd be interested in any setup information you could provide. The distributor has a single black wire coming out of it. Is that the hot line and connect to the positive terminal on the coil? Also, the wire is cracked and kind of brittle. Can I just replace it with any new wire as long as I plug the hole in the side of the dizzy? Or is there an official replacement wire that has the plug for the hole integrated like the original? Part of the reason I wanted to attempt this setup was also to educate myself, so any knowledge you can pass on is appreciated. Thanks!
__________________
1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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Old 03-31-2019, 03:06 PM   #10
mbiver
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Question Re: Change 1977 345 to Prestolite points distributor?

Here’s my current setup with the Prestolite and Petronix. There is a tachometer wire as well. I didn’t set this up and have no idea if it’s correct. The original 304 was blown 2 days after purchase from a used car lot many years ago. We came to an agreement that if I paid for a new engine, they would do the install for free. I found the current 345 in a junkyard for $200 and they installed it. Though I don’t know much about mechanics now, I knew next to nothing then so really don’t know if it was setup right or if the current dizzy was on the 304 or came with the 345. It did seem to run well at the time. Since I want to go to the Holley points setup anyway, I guess I’m just looking for the full correct setup and am willing to purchase whatever I’m missing from Jeff and team to make sure it’s done right and I learn the correct way.
__________________
1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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Old 03-31-2019, 08:21 PM   #11
Scoutboy74
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Default Re: Change 1977 345 to Prestolite points distributor?

The single wire coming out of the distributor goes to the coil NEGATIVE terminal. The tach feed will also go there.

Breaker points will over heat and eventually burn out if they are subjected to full battery voltage for very long. This wasn't a concern with your Prestolite setup.

You first need to determine which of the wires hooked to your Presto POSITIVE terminal is the switched feed from your key. It will be energized in key ON and START positions. You'll need to get yourself a cheap, illuminating test probe with gator ground clip if you don't already have one. Use the probe to test the loose wire terminations until you isolate the switched feed wire. Label it so you don't forget.

Next thing you should add to your tool arsenal if you don't already have one, is a handheld multi-meter capable of measuring resistance in Ohms. Set it to the lowest end of the scale. Then probe across the coil POS and NEG terminals. You should get a reading of 1.x Ohms primary resistance. Now, subtract that reading from 3.3. The remainder will be the value of ceramic ballast resistor that you will need to purchase from an auto parts store. For instance, let's say your coil measures 1.5 ohms across the terminals. That would leave you needing a 1.8 ohm ballast resistor to make up the difference. The Primary resistance of the coil, plus the ballast resistor to make the proper total resistance, will reduce the voltage to the coil and the points enough to protect them from overheating. But we shouldn't assume your coil primary resistance is what it needs to be. Measuring is the way.

Once you've determined your coil primary resistance and purchased a ceramic ballast resistor with the right value to get you slightly above 3 ohms total resistance, you'll need to mount the resistor to the firewall where it can be reached by the wire that you previously identified as the switched feed. Trace that wire back to the bulkhead connector at the firewall. Then run a few inches of the wire over to the ballast resistor. Cut the wire and affix a termination that will allow you to connect it to the nearest side of the ballast resistor. Affix the same type of termination to the other loose end of the wire where you clipped it in two. Attach that end to the other side of the ballast resistor. What you've done is interrupt the switched feed wire with the ballast resistor. In other words, the switched feed voltage should now pass through the ballast resistor on it's way to the coil.

Scouts older than yours that came originally equipped with points distributors, used a special resistor wire of a specific length to provide not only the switched feed to the coil, but also serve as the ballast resistor. Your Scout doesn't have this resistor wire, just a normal wire. That's why you need the ceramic ballast resistor instead, to complete your points distributor retrofit.

Now, you may find once you've done all this, that your engine will occasionally have some difficulty lighting off during that initial cold start of the day, especially during colder times of the year. To combat this, you'll want to run a new length of 14 gauge wire from the starter solenoid 'R' terminal, which you can either run up to the coil side of the ballast resistor, or all the way to the coil POS terminal. Either way, the choice is yours. This wire will be a momentary ballast resistor bypass feed. What it will do is allow full battery voltage to reach your coil only while you are starter cranking. Once the engine lights off and you release the key from START to ON, the ballast resistor feed will take over, once again providing a reduced current to your coil while the engine is running. So that will mean you have two switched power feeds to the coil. One for starter cranking and one for engine running.
__________________
Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW - "Pull Lemuel, pull!"
Organ Donor - '72 1210 Reg Cab 2WD - 392/TF727/4.10 RA17/7500# GVW - "Use my body to keep you alive!"
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW - "Mongo love candy! Duh, huh, huh!"

Last edited by Scoutboy74; 03-31-2019 at 08:29 PM..
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Old 04-04-2019, 02:35 PM   #12
mbiver
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Default Re: Change 1977 345 to Prestolite points distributor?

Thanks a lot, Scoutboy74. Got my dwell/multimeter last night and will start looking at the wires. Might take some time, though, since Iíll be moving in the next couple weeks and not sure how much I want to tear apart. Probably wait until after the move since it does run now and I donít want to have to pay for a tow.
__________________
1978 Scout II with 1977 345 engine
Four wheel drive Dana 44 Axle's, Dana 20 T-Case, Power Steering, Power Brakes (Disc/Drum), no A/C.
Manual trans, Borg Warner 3-speed w/floor shift.
Prestolite distributor with petronix.
Fuel System: New 19Gal. Poly tank/Sending unit from IHPartsAmerica, Nylon fuel line, relined original fuel neck filler tube, rebuilt Holley 2245 Carb.
Unknown non-oem modifications
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