Reluctor Phasing

one of my first threads on this amazing forum was about an intermittent exhaust "poof" sound from the drivers side exhaust on deccel, and very sluggish take off under hard acceleration. Ive had this annoyance since i swapped a V8 into my early-A. i had many awesome tips and things recommended to diagnose and try. nothing really made a HUGE difference, so being frustrated and miffed, i left it as is. ive been driving my beastie for 2 years, and its been a fun 2 years. so, having done literally every modification, tweaking, setting, checking, whatever, that has been recommended, or ive read/heard, i thought...."ya know what, i really havent checked the phasing in the distributor....oh damn." so, did the ol hole in the cap riggamoram, fired the beast up, and HOLY MOSES BATMAN!!!! the spark from the rotor to the cap was HUUUUGE!!!! the rotor was pasing the cap tower before it would fire, so the spark was jumping back. definitely not right. so, i set the engine to TDC 1, (yes i verified with a piston stop, that was one of the recommendations from the get go) i think it was dale (right?) 67dart23 that mentioned that, and set the reluctor with the pickup unit dead on, so my timing was as close to zero as i could possibly achieve. fired it back up, spark was still MASSIVE in length (im talking 1/8th inch or better) it was idling rough (to be expected) so i hooked up my vacuum gun to the vacuum advance (it puts in 14 degrees) and sucked er down. low and behold the spark was perfectly lined with the tower, and it was much more responsive off idle than ever before, and idled like butter. so, since the timing changed 14 degrees at the crank, then the reluctor to rotor is off 7 degrees, right?

One last thing i tried was switching the pickup wires on the distributor, i double checked before i switched them, and they were correct on the polarity. with the wires reversed, the spark was right on. Neato. set my static timing at 11, (distributor puts in 23 degrees) and went to check my "all in"........it went to outer friggin space....i had to set my static at -9 ATC so my "all in" was at 34. and no, my vacuum advance wasnt hooked up, nor was it connected to my vacuum gun. im assuming the reluctor signal was being mis-read due to the wave-form being reversed, causing the box to fire before it should have, changing the amount of advance? does this seem right? i was a bit confuzzled on that one.

anyway, i switched the pickup wires back to the way they should be, and my timing was dead on. 11 static, 34 all in. neat. i have a "corrected reluctor" on order from rick ehrenberg on Ebay, so i shall chime in wednesday when i get it installed and see how it does. just wanted to share my happenings with you fellas, and maybe get some thoughts or pointers. cheers.:drinkers:

Check this: I believe you can flip the reluctor on the shaft for a 'reverse rotation' B/RB app or an LA app, really! It may even be marked like that. That'll change the reluctor phasing for sure. May be just what you need. reversing the polarity changed the pickup from trailing to leading edge (or vice-versa) thats worth a few degrees.

i just checked out on the shop phista to see.....it re-positioned the reluctor the perfect amount.....the wrong way....NOOOOOOOOO!!!!!!!!!! :banghead: but hey man that was a very good thought. thank you!!!

You explanation troubles me.

No, not that first, below EDIT THIS FIRST this one up HERE. HAVE YOU CHECKED that the reluctor is assembled correctly? There are TWO keyways. There should be a directional arrow indicating proper rotation. YOU WANT the key in the slot matching your CW rotation. (This is because that same pickup is used on B/ RB engines, which rotate the opposite direction and must be offset

First pay no attention to the pickup wires color IF YOU THINK the phase is off. It might be the pickup was assembled wrong, with wrong magnet polarity

Second, TIMING has absolutely nothing to do with phasing.

Phasing is the relative relationship between the rotor and "when" the spar happens. This means that REGARDLESS of timing, if you reverse the pickup wires polarity and the phasing improves, THAT is correct.

THEN set your engine timing LAST

10-4. as of right now, the roll pin is in the corresponding slot to the correct arrow with the 2 lines, as it was in the beginning. your aforementioned order of switching the wires, observing that the spark pattern improved, and setting the timing last, thats exactly what i did. BUT, i had to set the static timing at -9 or it would severely over advance. now even though it was set at -9, the spark from rotor to cap stayed the same as it should, nice and short......if switching the wires was correct, how can i keep the timing from advancing 43 degrees instead of the 23 its supposed to? would the pickup read the trailing edge of the signal before the peak? causing another 20 degrees to be added?....that seems a little bonkers to me....and believe me, i double and triple checked that to make sure i wasnt losing my mind, and confirmed it when i switched the wires back. initial timing set at 11 degrees, for reference sake, no vacuum advance, wires switched, awesome rotor to cap spark pattern, i was at 54 degrees all in at 3500, wires back to original, sheisty rotor to cap spark pattern, 34 all in at 3500...this hurts my head.....

The poof sound you are chasing may be a lash setting too tight, or burned valve from that. Can't fix that by messing with ignition.

About changing wire polarity on pickup. The electronics for the trigger sense must see a negative dip then go positive. The negative happens when the reluctor tooth passes the coil pole tip, draws magnetic flux, the voltage drops to zero, at the trailing edge the flux increases and ignition is triggered. That is correct polarity. Check it by setting the crank point for static timing that you see at idle with light, then check the reluctor tooth vs pickup pole, it should be near trailing edge. If it is clearly in the gap between teeth, then the polarity is wrong. Wrong means cap phasing will be off, and tigger point will wander greatly, because the flux between the teeth is not changed abruptly, except for runout, or noise triggers. The trigger point will likely vary timing from cylinder to cylinder.

Kit knows his chit. Even though half his vernacular is foreign to us! Hahaa! drill out the rotor flat and pin it wherever you see fit. while you are in there make sure gap is set. The vacuum advance will have a number of the arm, maybe you need to change that (or adjust with allen wrench if possible through inlet) to a different value.

This is a mind-bender, but the rotor tip to reluctor lobe relative positions are fairly fixed (assuming no extra-ordinary means), but the pick-up core to cap terminal relationship is variable. Changing this can help with rotor phasing IF there is enough vacuum advance travel left to not limit that. Where the pick-up plate stops at rest (no vacuum advance condition) can be changed to better align the cap's terminal with the rotor tip. Recognize that the vacuum advance can messes with this, so given the choice set the stop such that vacuum advance initially moves the rotor tip towards the cap terminal rather than further away from it.

There are other considerations, so this isn't going to offer a large range of change, unlike the Ford D-S II's pick-up plate's pivot design, but is another tool in your pocket.

I've been using the "1/2 past the pick-up's core with the reluctor lobe's trailing edge" to static time Fords and Toyota's (actually Toyota converted ACVW dizzy's) for years. Not sure where or how I came to find it to work so well, but with those systems the width of the relative parts makes this easy to do.

i seriously dig the info here. i owe all of you many thanks, and as of now, i believe i have it figured out. i received my corrected reluctor from rick ehrenberg today in the mail, and adjusted the rotor tip with the "15 degrees before the tip" pin slot. effectively advancing the signal to fire, changing 15 degrees at the crank, 7.5 at the distributor, making the rotor line up dead on with the tower upon firing. just like i figured with the timing changing 13 degrees at the crank, 6.5 at the distributor, with my vacuum advance sucked down, lining up the rotor with the cap perfectly in my initial jump into this project. i am beyond happy with the difference in driveability. its much more snappy, and the bog is gone. my static timing at idle is 10, and im 33 all in. i checked the reluctor to make sure the pickup is on the trailing edge of the reluctor tooth at 10 btc #1, to confirm the pickup wires were correct, they are. im beyond happy right now. thanks again guys!!

Somehow I missed you had picked that device up. What bothers me is "what causes this in the first place" because it's a huge error to just chaulk up to manufacturing tolerance, etc.

i agree on that part. whats troubling to me though, is i have four extra main shaft assemblys from a 74, 76, 79, and 87 smallblock distributors, and not a single one is the same clocking position for the reluctor roll pin to rotor clocking slot. all of them were close, yes, but none of them were the same....i know the 87 is a different monster than the rest, being from an ECU setup, but the 70's ones were all from single pickup, ignition box setups, and had the same reluctor. why would they vary throughout production? i just don't get it....did the factory play horseshoes and hand grenades? :dontknow:

The best way to verify phasing is to punch a big hole in a spare distributor cap and shine a timing light to see where the rotor is relative to the tower when the spark fires. The Holley XR700 manual (download on-line) details this. Simple. You can see similar on youtube, I know there is/was an MSD video.