Rev limiting rotor causing low rpm hesitation

[SpeedracerIndy]

My RoW SC uses a rev limiting rotor to limit the rpms, unlike the US SC which use a fuel cut relay in the dash. I broke my original one a while ago, and have been running with a standard SC rotor all winter. I just got a new rev limiting rotor from Pelican a few weeks ago, and today I put it in and drove it until the oil temp reached 180 for the first time in a while. I noticed a bucking when taking off from a stop light with the rev limiting rotor once the engine was up to operating temp. I noticed this with the original rev limiting rotor as well last sumer, but didn't attribute it to the rotor at that time. Well, when the standard non-limiting rotor was in the car it never did this (and I did get the car up to full operating temps with the standard rotor several times as well). As soon as I put the new rotor in the car, it started bucking when taking off at idle. I have to slip the clutch at about 3000 rpms to prevent the car from bucking with the rev limiting rotor. I know I ordered the correct part, I looked it up on PET to be sure. I have also compared the rev limiting rotor to the standard US spec SC rotor, and aside from the rev limiting feature, the dimentions are identical as far as I can tell. What is there about this rotor that would be causing this, and has anyone else experienced it?

Also, is there any way to incorporate a rev limit into my RoW SC without using the rev limiting rotor, and without replacing my CD box with an MSD? I don't like the idea of the car having no rev limit, but I also don't like the difficulty taking off from a stoplight at idle.

[SpeedracerIndy]

bump

[Joe Bob]

Not likely...but the rotor you have may be defective....it uses centrifugal force to cut spark....it could be grounding at lower rpms.

As to other rev limit options...other than a rotor or a CD box change...dunno of anything else besides a tennis ball under the gas pedal and self restraint..... %^B

[Jeff Higgins]

Did you re-time it after the rotor swap? I'm not sure that the nose on the rev-limiting one is clocked exactly like the non-rev-limiting one.

[SpeedracerIndy]

Originally posted by mikez
As to other rev limit options...other than a rotor or a CD box change...dunno of anything else besides a tennis ball under the gas pedal and self restraint..... %^B

That's pretty much what I thought, but I thought I'd ask. Restraint works pretty well, but after getting into the 911 from driving my daily driver all week, that tach climbs to 7k pretty darn fast!

Originally posted by Jeff Higgins
Did you re-time it after the rotor swap? I'm not sure that the nose on the rev-limiting one is clocked exactly like the non-rev-limiting one.

hmm... I didn't think about that. I did not re-time it. When matched up the rotors look to be the same, but the rev limiting rotor could easily be a little off. I guess it's time to get the hearing protection out and check the timing.

[Grady Clay]

Before you do anything else, have you put the non-rev-limit rotor back in and confirmed the problem goes away?

A few swaps back and forth will insure you are interpreting the cause and effect properly. You don’t want to go down the wrong path.

Best,
Grady

[MotoSook]

A defective rotor would be a good guess, but Grady's recommendation is right on! If the solid rotor doesn't cure the problem, then I would suspect the vacuum retard/advance pots.

[SpeedracerIndy]

I did swap the other rotor back in and the problem did go away. I only did it once though. I will try a few more swaps to be sure though. The strange thing is that this is the second rev limiting rotor I have put on the car and it behaves the same way the first one did. The rev limiting rotors are also much tighter fitting on the distributor than the non limiting type. I really have to push them on hard to get them on there. I wonder if they are not seating all the way down on the distributor like they should. Thanks for the suggestions.

[MotoSook]

Just a WAQ...did you install the new rotor correctly? If you had to push so hard to get it in, the thing may not be seated right...making your timing a bit off. Of course checking the timing with a light is always a good idea.