Does Pertronix require timing readjustment?

tee jay

tee jay

Member
Hi all,I installed a pertronix II in my 345 back in November and just now got to fire the engine with it. It runs fine, but it don't start like it did with points. It cranks hard like the timings off? Do you have to reset the timing after installing the pertronix?
 
Just doing a conversion shouldn't require a timing adjustment, but perhaps the distributor got rotated sometime between the last time you started it with points and now? I know with my crane module there was an air gap that I had to set. Idk if the pertronics is similar in that regard. Those are the only two things I can think of.
 
Imo, putting a pertronix in is the same as changing the points -- the timing should be checked / reset (though a mechanic put the pertronix in my t/a.).

You also might want to double check the wiring -- I know the pertronix has "extra" wires.
 
Any and every p-tron install will be slightly different even in the same distributor. These devices are infinitely more accurate as "trigger" devices in an inductive ignition system than any breaker point/condenser system can be.

When you set the "air gap" during your p-tron install, that actually locked in the dwell factor. In the case of a p-tron 1481 module, inna Holley points distributor, you used an included tool (the small sliver of clear acrylic) that measured 0.030". That creates a dwell factor of 30* nominal, same as setting the breaker point gap to say 0.017". In fact, you can connect a dwell meter to the coil right now and it will read exactly the same dwell factor as what a correctly adjusted set of breaker points would. If you connect an oscilloscope, you will also see a much more accurate dwell reading representation. A dwell meter is highly buffered and displays an "average" reading, a scope shows the actual event and will also point out any variance that is created by a worn distributor or mechanical advance unit. I wish I had a digicam that is fast enough to shoot a "freeze frame" pic of the scope screen so you could see this!

And anytime the dwell setting (either with breaker point adjustment or p-tron install) is changed, the point of occurrence of the spark event is changed also...or as we normally say..."the timing". To take this a step further...if you installed a crane optical trigger conversion, or a crane xri lobe sensor trigger conversion, or even installed a replacement pickup inna Holley gold box distributor, the air gap/"phasing"/etc. That is part of that process determines the dwell factor. To take that much further, if ya incorporated an ignition "box" (capacitive discharge system) along with a companion "timing computer" such as the msd system or a similar system from mallory, then the computer can control timing. This type system has nothing to do with "fuel injection".

So the short answer...yes...you must verify (and then most likely adjust) base timing anytime the breaker points or electronic trigger is disturbed. The actual timing factor is no different for the engine just because the trigger device has changed.

I do not use a timing light to set/determine base timing. I "power time" stuff I set up, and then come back with the timing light and actually see what the factor is after that. That is performance tuning methodology and has nothing to do with tuning for emissions levels.

I do use a "dial back" timing light however if I'm trying to determine...or verify, the distributor advance actuation or curve, and that must be done in conjunction with an accurate tachometer like a "shop" tach. This is redneck methodology for those of us who don't have access to a distributor machine!

This is a very good question...one I receive quite often in email so I know it's a greatly misunderstood subject.
 
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Very vauleable stuff micheal,I try to ask good questions when I can and I try not to bother anyone with my dumb questions!! I even have a old dwell meter back in the corner of the garage with an inch of dust on it, I need to check that out.
If you see dave the gear guy tell him excellent job on the power lock, I love it!!
Tj
 
Hey Mike, not trying to hi-jack here, but I'd love to see your comments on "power time" on an sv and how that's done. I've heard the term and have heard various arguments but a little illumination from you would be great.
 
tee jay said:
very vauleable stuff micheal,I try to ask good questions when I can and I try not to bother anyone with my dumb questions!! I even have a old dwell meter back in the corner of the garage with an inch of dust on it, I need to check that out.
If you see dave the gear guy tell him excellent job on the power lock, I love it!!
Tj
Click to expand...

Dumb questions ain't dumb if tha asker don't know the answer! That makes 'em just "questions"! Otherwise, there would be no reason for this sandbox to exist for us to play in!

I showed dave the pics of your rig when he was here for dinner Wednesday nite...momma's got a pork roast in the oven now so I'm sure dave kin smell it upriver, so he'll be here today right at grubthirty...he always knows when to show up!
 
lou said:
hey Mike, not trying to hi-jack here, but I'd love to see your comments on "power time" on an sv and how that's done. I've heard the term and have heard various arguments but a little illumination from you would be great.
Click to expand...

Ok lou here goes...and this deal ain't no black majik kinda secret process that's only used on them backwoods hillbilly dirt tracks across amerika! My mentor (the old german blacksmith) taught me this in regards to my pop's '60 valiant/225 after I'd fooked up the points and distributor trying to teach myself how to do "tune-ups", I was 13 and had scruud pop's car over bad while he was out of town! And it's not approved for use in kalifokneekate for smoggin'!!!

Purdee simple...only after Setting dwell (or breaker point gap) to the required spec, loosen the distributor hold down enuff to allow rotation by hand with considerable force applied. If the distributor has not been touched in decades onna I-4 or sv, don't be surprised to find it frozen in place due to mung and a century of ratpiss rain on it. That's a whole other issue to deal with! I know lou cleaned the ratshit off his motor many years ago, he's had plenty time to handle that, whenever me an lou hook up I do a ratshit inspection on his stuff.

We also gotta assume here that the distributor guts are in nice shape, mechanical advance is free and not worn out, the end play is minimal, the breaker plate rotates smoothly when called upon, the vacuum advance system is functional, ya don't have a dam prestolite cap onna Holley or vice-versa, blahblahblah...

All this rhetoric is also based on the use of whatever passes for "regular" grade alkeegazz in yore market and a carburetor that is in "average" condition with no jetting issues. This shit has nuthin" to do with electric carbs or what Craig calls "efi" and all the hocuspocus that goes along with that, I don't need no dam pooter fookin' with my sparkmaker when goin' down the road!

Crank tha motor and run it fully up to temp...that means git the oil hot...not just the coolant temp!

Then rotate the distributor slowly for and aft (all these IH motors when used in motor vehicles rotate the distributor clockwise), as ya "retard" (or as I sumtimes say..."back off") the timing, then the idle rpm will drop. If ya "advance" the timing (or as I say, "kick it up") by rotating the distributor, then idle rpm will increase. Do that several times to get the "feel" for what's happening, but not so far either direction that the engines stalls. It's not possible to cause any kind of engine abuse when doing this!!!!

If it does stall, then put the distributor back where it was, re-start tha motor, and do it again! Do not leave the ignition switch "on" without the engine running! If you are running almost any kind of electronic trigger conversion, that can damage or fry the part. If ya do that with breaker points, they will quickly overheat and go through meltdown! If you are running a sooperdooper ignition "box" with an electronic trigger, most of those incorporate an internal circuit that turns them off after a slight period of inactivity for protection. So ya might have to go through a "switch cycle" or "as you pootercar drivers say, "key cycle", for 'em to come back to life.

So after ya gotta feel for this distributor rotation thang...simply rotate it to increase idle rpm to the point the motor starts sounding kinda rough and "gallopy", that's too much base advance! Back off from that point until is smooths out and sounds like the motor in yore table saw! Do not screw with any carb adjustments here!!! We ain't done!

Now just go out for a test drive! And yes, I do this with my hearing aids installed, otherwise I can't listen for/hear what we call "knock" which izza fanceeazz term for detonation!

So...if ya "advanced" the distributor to the right spot, as soon as ya nail the loud pedal hard, yore gonna be greeted with major ping! That is good, that means ya did sumthin'! But that is now yore starting point...the fun begins! Don't do this with the whole famdambly in the rig, they will git bored real quick! And do it out on sum back road where ya kin stop and go and stop and go and stop and ...over and over, and pull off the right of way to make "adjustments" on the fly. A good spot for lou to do this is on that road from furnace creek to beatty in death valley, that goes up daylight pass. That grade is part of all oem manufacturers' "secret" test loop every summer!

So the whole idear here is to keep doing this over and over until the ping/detonation/spark knock is eliminated under full and partial throttle app, when the engine is under load. Then back off the timing a scoshe more for "insurance" against fuel octane variables that occur every time ya fill up.

Bet ya find the sob is much more peppy! But it dam shore won't pass smog! For instance...a "typical" sii/304 package will have a base timing "spec" of say zero degrees btdc, ya can see that on the smog sticker under the hood if it's still there...or look in the book. If ya use the described methodology, and then hook up the timing light, I bet ya will see somewhere between six and ten degrees btdc. this procedure is not smog compliant!!!!!

Ya ain't done...make dam shore ya snug down the distributor now at yore new sweet spot! Then...ya will also notice the curb idle speed is way too high. Back off the curb idle adjustment, onna sv motor with manual tranny, I use 550>600 rpm. With a tf 727 tranny, I use 700 in park/nuetral.

Now ya can touch up the idle mixture screws on the carb, and ya will have to keep ditherin' the idle speed at the same time. I bet ya find that the idle mixture screws end up landin' inna totally different position! This is why ya only screw with a carb after the ignition system is completely locked down! If ya wanna use a vacuum gauge for this, then that's even better so ya can see what is going on.

And after some more test drives if ya pull the plugs for a color check, ya May see a need for a slight re-jet of the carb also if you wanna get it ragged edge!

Let me reiterate...this is performance tuning and is not in the same ball park as tuning for smog or to oem "book" specs. If...your rig is totally original, and all "smog devices" are functional and connected properly, in other words basically a virgin, then this procedure is not in your best interests.

However...if ya did put this rig onna smog machine ya might be real surprised at the final numbers! Too bad the "air quality" folks just don't get it, who gives a shit if the dam cat is installed if the fookin' numbers show it's runnin' clean????
 
Ok, my timing was at 10 degrees with the points and after pertronix it was at 28 degrees. I kinda thought maybe it would be a little off but not that much? Just thought I would post that for future use if anyone else wondered how much it would change it?anyways, its back to 10 degrees and running up to par.
Tj
 
Just to be redundant...

You would probably see a similiar "timing change" replacing points / other "pickups" - not just the pertronix.

You would be extremely lucky (or good) to have the timing stay the same.
 
tee jay said:
ok, my timing was at 10 degrees with the points and after pertronix it was at 28 degrees. I kinda thought maybe it would be a little off but not that much? Just thought I would post that for future use if anyone else wondered how much it would change it?anyways, its back to 10 degrees and running up to par.
Tj
Click to expand...

Not surprising at all! And it just as well coulda been off the opposite direction also...and would not have come anywhere close to even starting...just spittin' back through the carb!

I went through this same thing with a close friend over the phone for two days a few weeks back!!! He just couldn't git his haid around "why" since the two screws located the p-tron "accurately". But in actuality, there is much fudgefactor in the optimum location, this is the reason for the "adjustability" of the p-tron mount in the first place.

Another example is mounting a p-tron inna delco distributor like hooty's...the install is nothing like what is done on the Holley distributor. There is an air gap to verify, but it's "adjusted" through a magnet wheel shimming operation, is more tedious than installing the p-tron inna Holley sparker. That's why the I think the crane xri conversion is the best for a delco for the average diy'r. But performance-wise there is no advantage to one over the other, both are nice improvements.
 
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