Slick 60's

I recently bought a 66 f100 with a 352. The ignition points have been replaced with petronix electronics. The truck has been hard to start every since I brought it home. Carb is new rebuild and not the problem. I have not checked ignition timing yet, but once truck is started. It runs pretty good with no lag or pinging.

Even with a new, or the old, cap and rotor, I have a very strong spark from the coil wire while cranking, but a very weak spark from the new plug wire. Upon inspecting the old distributor cap and rotor, burn pattern inside the cap indicates that the coil is not firing until the rotor has already just passed the corresponding plug wire terminal. It appears that the spark then tries to jump back to that terminal, leaving a burn pattern in its path.
I am wondering if the distributor gear could be off one tooth, and the distributor must then be turned past its normal range to get the engine in time.

Is this distributor gear designed so it is possible to be off one tooth?

If it was off 1 tooth , it would change your timing ,just like turning your
Distributor several degrees

If it runs good after starting, my guess is your timing is close

Full Voltage to coil while cranking is important, for easy starting

Make sure you have full voltage at startup (unless pertronix does not work that way)

check the ignition timing

What do the spark plugs look like? If they are worn it will be hard to start when it is cold and damp outside.

Check your timing before you do anything else. I put a Pertronix in mine and it changed the timing 16 degrees. Must have something to do with the pickup in the electronic set up being in a slightly different location than the thing that opens and closes the points.

Oh and it started hard when it was warm. Adjusted the timing and it runs better than ever

HERE I the way I have done any FE Motor,, take # 1 plug out, let it pop with finger in the hole so its top then get your timing mark up on TDC, when this is done the rotor has to be pointing toward # 7/8 spark plug then stick dist back in,, when motor is running the vacuum advance should have plenty of room to adjust so it does not hit thermostat housing to keep it running,, if its up against the housing then its tooth off and will cause engine to run hotter than normal

It is not unusual to have that situation with an electronic pickup. MSD makes adjustable rotors for some applications to "synch" this, but it takes some doing. Modifying the cap location also is doable; changing to the later model two-piece cap and "trimming" both locator tabs on the caps may allow for enough adjustment for an improvement. After setting the timing to factory spec, or slightly advanced beyond that, you can use your old cap with a hole drilled just inboard of #1 terminal for a reference. simply hook you timing light up as normal and aim at the hole. the strobe should allow you to determine just where the rotor is when firing.
If you have the original Pertronix (I), it is designed to operate at the reduced voltage provided by the factory resistor wire, but still needs full available battery voltage from the bypass wire to coil during starting. Pertronix II is designed for full available battery voltage at all times, so should have the original resistor wire replaced by a full voltage wire from the ignition switch.
Paul

Thanks, all---- I'm just going to go "old school" for the time being and go back to a set of points and condenser. That way, I will know where the rotor is when the points start to open! I may put the Pertronix back in later.

Also-- What is the idle speed and degree advance to set the timing on this engine? (I purchased a "1966 FORD TRUCK Shop Manual" on computer disc, and so far it has been pretty much useless for finding such basic information.)

Toyz -- Great trick drilling the old cap to see where the rotor actually is when the plug fires!

Curb idle with the manual is 675 rpm (C6TF-R dist), automatic in gear is 475 (C6TF-C dist). Base timing is 6 degrees btdc, but the book allows 5 degrees either direction (as applicable). I suspect the majority of running on good fuel will end up at about 10-12 btdc base, allowing 34/38 degrees total.
I wouldn't toss the Pertronix, personally; I suspect getting full voltage (if required) and tweaking the timing will probably lessen the starting issue considerably. It certainly wouldn't hurt to see it performs with the standard setup, however.
I, too, dislike the disc manuals; thought it might be a generational thing
Paul

Why is everyone so reluctant to put a timing light on an engine? You see it time after time. Don't start ripping parts out, just learn to tune it.

SPark

^^^^ I agree
I should have said to check the timing
A timing light is a good tool to have

Don't put the points back in, time it. Simple as that. As I said

If your running the original C4 ballancer with intergrated single belt groove its possible the ballancer has spun 350° +/- placing the timing marks too fast. I would find TDC with a piston stop first then follow above advice.

As Steve and Pat stated, we are probably suggesting over-correction for normal states of affairs. The lack of alignment between rotor and terminal is probably of little concern, other than indicating the need to replace that cap and rotor. The Pertronix WILL change the timing, as will any point adjustment or replacement. I've never seen 16 degrees change; if I did with the correct Pertronix, it would go back to the WD, since that is likely to put the rotor waaaaay out of synch. Resistance type secondary winding will reduce the spark intensity at the plug, so that also may not be a concern.
Check for correct voltage at the primary wire going to the coil, both in start and run positions, and remember this needs to be done with the - side of coil grounded to read correctly. If you have correct voltage, go ahead and set the timing. That procedure is apt to fix your problems with no further effort.
If it doesn't fix the problem, call back!; we certainly can cover all possibilities!

Paul

End of story! -- Took out the Petronix, put in a new set of points and condenser. set idle timing at 8 degrees BTDC. Now I can reach thru window, bump the key, engine is purring.

I think Skid and LM14 missed my point.--- When engine timing was set correctly, the rotor was so far past the corresponding contact in the distributor cap, it was only able to send a very weak spark to the plug.

I know a lot of people love the electronic spark controllers. I think whoever installed this Petronix system before I owned the truck, may have installed the wrong unit. I sent a question with part numbers to Petronix asking if this was the correct unit for this engine, but have not yet received a reply. Since I will probably drive this truck less than a thousand miles a year, the points will probably stay. I also have a 65 Falcon daily driver, a 47 Willys CJ2A, an 5 tractors from 1926 to 1960. I think that keeping these old vehicles running in their stock form is half the fun!!! Thanks everyone!!

Not quite end of story; If this was a Pertronix I, then probably nothing has been changed; if a Pertronix II, it SHOULD have been converted to full voltage bypassing the original resistor wire. If that is the case, it will quickly burn up the points without the resistor. Also, even though you seem satisfied with the current performance; dwell should be set as that can make a big difference in overall performance and economy.
Crawling down carefully from soapbox!
Paul

Toyz -- I'm pretty sure it was a Pertronix I, The truck still has the resistance wire from ignition switch. Voltage at the coil with the engine running is around 7 volts. Voltage during cranking is closer to 12.
Your comment about quickly burning up points brings up and old question. On several of the old tractors I have owned, I have swapped 6 volt generators for 12 volt alternators so I could run more lights, and brighter lights, plus have more kick for starting in bad weather. In recent years, I buy a modern "12" volt coil and still must run a resistor to avoid burning points. If my fading memory serves me, many years ago, I could buy a 12 volt coil that was designed to run without a resistor, on 12 volts, full time, and not cook the points. It seems I remember when automakers were first switching to 12 volts in the fifties, there were some cars and/or trucks that used a straight full-time 12 ignition system. Am I imagining this??

I think you could buy a coil with an internal resistor,dont know if there still available. Maybe toyz or someone here knows for sure.

WE still run points in our Mercury,, I put a new set in for slick stock in Kansas,, then last year for Iowa I put another set in,, I do not use a feeler gauge I set by eye and timing light ,, I have a new Snap On Timing Light someplace I bought 30+years ago never used since I was taught to set points by eye, set timing by ear and carb mixture by hand on valve covers,, just like on any of the Fords getting the tooth right on the dist. if not different problems can occur

Darn, Tom, guess I'll throw away my distributor machine I've always been a "seat of the pants" mechanic, but it is amazing the difference in outright performance; and point gap, by setting the dwell into spec, correcting the advance curves on both centrifugal and vacuum, and bumping the timing up to that same point you are obviously approaching. The old time "scope" is a good tool in seeing just what is going on with the dwell, cylinder by cylinder.
Paul