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Does indexing a rotor affect A/F ratio? #2868916 01/04/21 04:07 PM 01/04/21 04:07 PM
Joined: Aug 2008 Posts: 4,066 Mo. racerx OP master
racerx OP master Joined: Aug 2008 Posts: 4,066 Mo.	I want to say yes.........but i will like your thoughts on this?

Re: Does indexing a rotor affect A/F ratio? [Re: racerx] #2868951 01/04/21 05:17 PM 01/04/21 05:17 PM
Joined: Feb 2008 Posts: 714 Central TEXAS!!!! sr4440 super stock
sr4440 super stock Joined: Feb 2008 Posts: 714 Central TEXAS!!!!	nope, once the fuel is mixed with the incoming air the A/F ratio is set. now you can get a different reading depending on where the O2 sensor is located and the timing of the spark, but the ratio hasn't changed. Joe Without Data, you’re just another guy with an opinion.

Re: Does indexing a rotor affect A/F ratio? [Re: sr4440] #2868978 01/04/21 06:20 PM 01/04/21 06:20 PM
Joined: Nov 2020 Posts: 18 deltona, fl. M mike laws member
mike laws member M Joined: Nov 2020 Posts: 18 deltona, fl.	Might want to give this one a little thought.

Re: Does indexing a rotor affect A/F ratio? [Re: mike laws] #2869050 01/04/21 07:37 PM 01/04/21 07:37 PM
Joined: Jul 2004 Posts: 19,317 State of confusion T Thumperdart I Live Here
Thumperdart I Live Here T Joined: Jul 2004 Posts: 19,317 State of confusion	Yep, exactly what I was thinking and I know for a fact phasing/timing can and does change afr's...... Last edited by Thumperdart; 01/05/21 12:35 PM. 72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....

Re: Does indexing a rotor affect A/F ratio? [Re: racerx] #2869057 01/04/21 07:55 PM 01/04/21 07:55 PM
Joined: Aug 2003 Posts: 43,097 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,097 Bend,OR USA	Any tuning done to the motor will have direct affect on how it runs so I'm sure a good O2 gauge should measure and display the changes My Innovate system did Now if you mean your going to change the rotor phasing and not the ignition timing at all then maybe that won't affect the AFR readings Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Does indexing a rotor affect A/F ratio? [Re: Cab_Burge] #2869085 01/04/21 09:12 PM 01/04/21 09:12 PM
Joined: Jan 2005 Posts: 2,540 Milwaukee WI T TRENDZ master
TRENDZ master T Joined: Jan 2005 Posts: 2,540 Milwaukee WI	Unless rotor phasing is so far out of whack that the spark jumps to the next post, no. It will have no effect. The rotor phasing and ignition timing are two separate things that are inter-related. The spark will occur at the same time in the cylinder regardless of phase. The exception to that is if phase is so far out that the spark doesn’t make it to the correct cylinder. "use it 'till it breaks, replace as needed"

Re: Does indexing a rotor affect A/F ratio? [Re: racerx] #2869134 01/04/21 10:56 PM 01/04/21 10:56 PM
Joined: Apr 2008 Posts: 117 Aus H hysteric member
hysteric member H Joined: Apr 2008 Posts: 117 Aus	Originally Posted by racerx I want to say yes.........but i will like your thoughts on this? What do you mean by "Affect"? The AFR your carb meters is set and cant be affected by ignition as Its a mechanical device. But a change in ignition will affect combustion and that could change the "AFR" your O2 sensor is interpreting. Last edited by hysteric; 01/04/21 10:59 PM.

Re: Does indexing a rotor affect A/F ratio? [Re: mike laws] #2869158 01/04/21 11:53 PM 01/04/21 11:53 PM
Joined: Jan 2003 Posts: 30,989 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 30,989 Oregon	Originally Posted by mike laws Might want to give this one a little thought. Mike, I don't recall ever seeing you on this board before. How is life after leaving Bo Laws? I'm not sure on the OP question. I do know that changing timing will change the AFR. I suppose indexing the rotor could also make a change but I'd be surprised if it was significant. I'm not exactly sure why the AFR changes when timing changes. I suppose that if the combustion becomes more efficient it changes the signal on the booster. With an EFI car when you change the timing the AFR stays the same. But, the fuel flow will change since the EFI system compensates for the change in AFR by adjusting the fuel flow. I've seen it work on the dyno but the percentage change is usually fairly small. Of course, the NASCAR boys would kill for a small percentage increase in BSFC.

Re: Does indexing a rotor affect A/F ratio? [Re: AndyF] #2869165 01/05/21 12:15 AM 01/05/21 12:15 AM
Joined: Jun 2006 Posts: 5,159 CT GTX MATT master
GTX MATT master Joined: Jun 2006 Posts: 5,159 CT	The answer should be no theoretically, but the reality is that you may observe a small change in measured AFR if it changes timing (or combustion efficiency) by a significant amount. If you see a large change you probably had an issue or caused one. Last edited by GTX MATT; 01/05/21 12:16 AM. Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street

Re: Does indexing a rotor affect A/F ratio? [Re: AndyF] #2869249 01/05/21 11:29 AM 01/05/21 11:29 AM
Joined: Nov 2020 Posts: 18 deltona, fl. M mike laws member
mike laws member M Joined: Nov 2020 Posts: 18 deltona, fl.	Originally Posted by AndyF Originally Posted by mike laws Might want to give this one a little thought. Mike, I don't recall ever seeing you on this board before. How is life after leaving Bo Laws? I'm not sure on the OP question. I do know that changing timing will change the AFR. I suppose indexing the rotor could also make a change but I'd be surprised if it was significant. I'm not exactly sure why the AFR changes when timing changes. I suppose that if the combustion becomes more efficient it changes the signal on the booster. With an EFI car when you change the timing the AFR stays the same. But, the fuel flow will change since the EFI system compensates for the change in AFR by adjusting the fuel flow. I've seen it work on the dyno but the percentage change is usually fairly small. Of course, the NASCAR boys would kill for a small percentage increase in BSFC. Hi Andy. Life is busy, thanks for asking.

Re: Does indexing a rotor affect A/F ratio? [Re: mike laws] #2869278 01/05/21 01:18 PM 01/05/21 01:18 PM
Joined: Jan 2003 Posts: 30,989 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 30,989 Oregon	Glad to see you stopping by. I still remember that Dominator that you built for me so I could test 2 circuit vs. 3 circuit and race gas vs. Q16. That was a trick carb and it worked great. I think it was the last carb I owned since I switched to EFI shortly after that test. It took so much work to run that test with a carb that it wore me out! Once I switched the engine over to EFI I was able to switch fuels by just typing a few numbers!

Re: Does indexing a rotor affect A/F ratio? [Re: AndyF] #2869287 01/05/21 01:33 PM 01/05/21 01:33 PM
Joined: Nov 2020 Posts: 18 deltona, fl. M mike laws member
mike laws member M Joined: Nov 2020 Posts: 18 deltona, fl.	I remember that carb as well. It was trick in it's day!

Re: Does indexing a rotor affect A/F ratio? [Re: racerx] #2869661 01/06/21 12:25 PM 01/06/21 12:25 PM
Joined: Mar 2007 Posts: 3,277 West Coast, USA jbc426 master
jbc426 master Joined: Mar 2007 Posts: 3,277 West Coast, USA	The experts on here have answered this. I will add that my MSD Pro-billet dizzy was so far out of phase that the tip of my rotor melted off and flew out at the track one day. The top of the rotor was physically melted where the metal was. The heat generated by my high output coil jumping that gap was intense. I put an adjustable MSD rotor in there and found it was nearly at the midpoint between the two terminals. 1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)

Re: Does indexing a rotor affect A/F ratio? [Re: jbc426] #2869676 01/06/21 01:02 PM 01/06/21 01:02 PM
Joined: Jan 2003 Posts: 30,989 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 30,989 Oregon	Yeah I found out about indexing the hard way back in the 90's when I was running a MP electronic distributor. It worked okay until the vacuum advance started to rotate things and then it would start shooting ducks. Took me a while to figure out the problem. I had to machine a new slot in the reluctor to fix it. I don't think Mopar Performance ever fixed the problem.

Re: Does indexing a rotor affect A/F ratio? [Re: AndyF] #2869685 01/06/21 01:12 PM 01/06/21 01:12 PM
Joined: Aug 2003 Posts: 43,097 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,097 Bend,OR USA	There where two slots (BB-SB?) on the rotor shafts to align the pickup wheel, I found more than one of them aligned, assembled, on the wrong one I would remove the distributor cap and see if the pickup aligned with the star wheel on the rotor shaft with the rotor tip aligned with #1 plug wire terminal on the distributor shaft If not moving the star wheel to the other slot would usually fix it Last edited by Cab_Burge; 01/06/21 01:12 PM. Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Does indexing a rotor affect A/F ratio? [Re: racerx] #2870017 01/06/21 07:14 PM 01/06/21 07:14 PM
Joined: Feb 2005 Posts: 4,310 Prospect, PA BSB67 master
BSB67 master Joined: Feb 2005 Posts: 4,310 Prospect, PA	Originally Posted by racerx I want to say yes.........but i will like your thoughts on this? Could you be more clear in your question? Are you asking: 1) does indexing a rotor affect the reading generated by an exhaust O2 meter? Or 2) does indexing a rotor actually affect the fuel to air ratio of the mixture entering the cylinder.

Re: Does indexing a rotor affect A/F ratio? [Re: BSB67] #2870130 01/06/21 10:02 PM 01/06/21 10:02 PM
Joined: Aug 2011 Posts: 2,853 Pattison Texas CSK master
CSK master Joined: Aug 2011 Posts: 2,853 Pattison Texas	Originally Posted by BSB67 Originally Posted by racerx I want to say yes.........but i will like your thoughts on this? Could you be more clear in your question? Are you asking: 1) does indexing a rotor affect the reading generated by an exhaust O2 meter? Or 2) does indexing a rotor actually affect the fuel to air ratio of the mixture entering the cylinder. THIS ^^^^^^^^ 1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5

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