So I lowered the Idle to around 900 and the car seems to run a little better. I can get it to rev to around 5.5-6k while driving then it does the sputter thing. Do you think that it could be my mixture? I attached the wires like the picture above and I think that helped a little too. The car does backfire when decelerating in gear and stinks like gas, would that make it rich or lean? I know the baseline is 2.5 turns out, is that on the adjuster where the choke pops out the bottom? What way do I adjust from the baseline to richen or lean out the mixture?

Oh, I also forgot to say.. I had my timing light hooked up and when I revved to the problem area the light would flicker. I guess this means I am not getting spark at the higher Rpms. How would I fix this?

  Cutlass372 said:

Oh, I also forgot to say.. I had my timing light hooked up and when I revved to the problem area the light would flicker. I guess this means I am not getting spark at the higher Rpms. How would I fix this?

If you smell fuel then you suffer incomplete combustion, e.g. the fuel is not completely burned due to a weak, too late or missing spark. I dont think that this is an issue of running too rich, the engine would not hesitate at higher RPMs with too much fuel. You did diagnose the issue with the timing light, there is no consistent spark available at higher RPMs.

Have you checked out yet how your plugs look like? If the engine is running rich, they will be black but dry. If they are wet and smell of fuel, its the ignition not doing its job.

Check out the installation of the Pertronix Ignitor module in the distributor, and make double sure the trigger sleeves alignment to the sensor is correct and that the trigger sleeve does not move or is loose or wobbly.

As the tacho is wired in line with the +12 feed from the ignition key, it might also be a source of trouble.

Try to remove the tacho wire (black/white stripe) to the coils (+) terminal, and directly connect a cable with +12 from the ignition key. (The green/white stripe cable leading to the resistor is wired to +12 from the ignition switch, so you could connect another wire to the green/white stripe cable and then the coils (+) terminal for this test).

Now check if the problem persists. No tacho this time so you have to run by ear.

Try this...put a multimeter across the coil terminals and measure the voltage as the engine revs. Should be 13~14V if you have no BR.

If it's less than that, it means that maybe you have bad wiring or a bad connection somewhere along the line of the power wire going to the coil. It's possible that with the low-voltage points/BR setup, this wasn't an issue, but with the new system trying to deliver a bigger zap it is noticeably running out of juice.

Ok, I set the timing at 10 degrees btdc at around 750-800 rpms. Checked my plugs and the rears looked normal to on the lean side and the front 3 were black and dry (rich). I checked with multimeter on the coil and it was around 6 volts at idle, around 8v at maybe 3-4k and 12+ around 5+. I couldn't see the tac so im am just guessing from ear. The stutter still happens at like 5.5k rpms. Voltage at the battery was 14v while running. Most things seem right except the carbs being not balanced. Should I move in that direction?

Ps: When I would rev high the multimeter would go blank, not say 0 but would go blank with maybe a dash. Was I just reving to fast that it couldn't keep up?

Thanks, Elliot.

Edited June 12, 200915 yr by Cutlass372

So, I noticed this thread when it began and read a few posts but saw that was being handled and didn't need my input.

Then last weekend my 240 began stumbling around 4-4.5K rpm and I revisited the thread to see if the problem might be related. The final solution is contained in the above title but first here's what I did:

I checked voltage at the battery and the Pertonix feed wire, I took out the GM 120 amp one-wire and had it checked (no issues).

The battery was 7 years old so I replaced it and installed a new fan belt.

Checked all the spark plugs, replaced the cap and rotor, and installed new fuel filters (Holley 100 micron before the Mallory 110gh fuel pump and stock fuel filter in the engine bay). Checked the fuel pressure and flow under load.

Disconnected the MSD - 6LA box and hooked up the Pertonix directly to the positive side of the new battery.

After each of these changes I took the car for a test drive. It got better but not perfect. I could drive it through 5,000 rpm but it stumbled when you pushed it hard.

Then last night after the 13 inning RedSox/Phillies game I had a thought.

So this morning I removed the covers on the Mukunis and found two of three of them had loose jets. Once tightened the car runs up to well over 100mph and has no hesitation at all.

I doubt this will help the original poster as i'm guessing he has stock SUs, but I'd think about looking at my carbs before doing anything else.

When you're a Jet.....snap, snap (go ask your parents).

The plugs on my '72 look the same (three are lean, three too rich), i need to balance the carbs too but that should be nothing to worry about. Still a good a idea to have the carbs checked if you suspect anything.

You did bridge the tach and the stutter still happens at 5.5K rpms, correct? So we can assume that the voltage supply to the ignition is ok, i would now focus on the distributor. Make sure that the pertronix installation is ok (sleeve, see above) and ideally have the distributor checked on a distributor tester, there might be a problem with the advance mechanism and or a worn axle.

When you rev your multimeter goes into panic mode :classic: For each ignition discharge your coil also induces a voltage on the primary side, so when revving you get around 200-400 volt at the primary terminals.

With a transistorized ignition such as the Ignitor you need to measure the voltage at the input of the ignition (ground & red cable of the Ignitor).

Edited June 14, 200915 yr by alhbln

http://www.classiczcars.com/forums/attachment.php?attachmentid=30321&d=1244665052

I wired the ignitor like this. I put the green/white and the black/white (the wires that came off the Ballast) together with a female connector. Then I put a male connector on the red ignitor wire and connected the three together. It's like the picture above, but I just didn't bridge them all together I just made it a connection. I will try to test the voltage at the red igitor wire tomorrow. I guess I can try to ground it on something else and just connect the red on the multi meter straight to that connection point.

  Cutlass372 said:

http://www.classiczcars.com/forums/attachment.php?attachmentid=30321&d=1244665052

I wired the ignitor like this. I put the green/white and the black/white (the wires that came off the Ballast) together with a female connector. Then I put a male connector on the red ignitor wire and connected the three together. It's like the picture above, but I just didn't bridge them all together I just made it a connection. I will try to test the voltage at the red igitor wire tomorrow. I guess I can try to ground it on something else and just connect the red on the multi meter straight to that connection point.

See the attached image for wiring the test without tacho. With your current wiring, remove the b/w cable to the coils (+) terminal (at this point, there should be no cable attached to the (+) terminal), and connect the wire marked blue in the image, leading from the Green/White cable to the (+) terminal.

You are now testing the ignition circuit without the tacho to check if the tacho in line creates problems at higher revs. Rev to 5.5K RPM (you need to do that by listening to the engine) and check if the engine hesitates. You might also want to repeat the test with the timing light and see if it still flickers at high RPMs.

So I disconnected the black/white from the coil, hooked up a wire from the place where the black/white and the green/white meet to the + on the coil.. No change.. I tested the voltage from a grounded point to where the red wire meets the others. I had a steady 13.75-14+ throughout the range (not sure if I hit 5.5k, but probably got close. I am going to call pertronix now and see what they say.

The 5500 RPM you hit, is that on the tach in the car ?, are you sure the reading is right, have you tried with a external tach (the shop kind).

Chris

  Cutlass372 said:

So I disconnected the black/white from the coil, hooked up a wire from the place where the black/white and the green/white meet to the + on the coil.. No change.. I tested the voltage from a grounded point to where the red wire meets the others. I had a steady 13.75-14+ throughout the range (not sure if I hit 5.5k, but probably got close. I am going to call pertronix now and see what they say.

So this should prove that the tach is not the culprit, also the measured voltage looks good! Next to the Pertronix call i would now focus on the distributor and check if the advance mechanism really works for the full RPM range and that the axle is not so worn out that it induces glitches in the Pertronix hall pickup. Have you checked the Ignitor module and sleeve installation?

A test run on a distributor tester would be the quickest way to go now, do you have a workshop in your area which could do this check for you?