[jlwdvm]

I am having some timing issues with my new 400 motor. It has a rebuilt distributor with a 5 year old pertronix conversion and an MSD cap with male terinals and new plug wires. The timing will be steady for 8-10 seconds, then become irratic for 1-2 seconds, then return to normal. I an using a Craftsman adjustable timing light. The motor will idle at 650-700 rmp. I have a blue and yellow adjustable Crane springs on the dist. weights that should start adding advance at 800 rpm. I hit each plug wire with the timing light and got good light at each. Bad pertronix? Bad coil?

[BVR421]

put some stiffer springs on the advance

[torqhead]

Originally Posted by jlwdvm

I am having some timing issues with my new 400 motor. It has a rebuilt distributor with a 5 year old pertronix conversion and an MSD cap with male terinals and new plug wires. The timing will be steady for 8-10 seconds, then become irratic for 1-2 seconds, then return to normal. I an using a Craftsman adjustable timing light. The motor will idle at 650-700 rmp. I have a blue and yellow adjustable Crane springs on the dist. weights that should start adding advance at 800 rpm. I hit each plug wire with the timing light and got good light at each. Bad pertronix? Bad coil?

This may be out in left field, but check and ensure you've got plenty of power (13v or close to it) at idle and of course up above idle you should be around 14.2. If your charging system isn't working right you can see effects like this, I've experienced this myself and noticed the aftermarket setups like MSD is more suspectible to this then a stock HEI.

[jlwdvm]

13 volts where?

[torqhead]

Originally Posted by jlwdvm

13 volts where?

At the power lead to the distributor. If this is an older vehicle and you haven't already done it I would put a relay in between a lead from the battery and the distributor itself. Use the lead that normally provides positive power (I chose those words carefully since on older vehicles they used a resistive type wire) to the distributor to energize the relay. The key is you want to have good power at the distributor or you will see exactly what you're talking about.

Now if you've already done the relay solution or this is in a newer vehicle (mid 70's or later), just checking at the battery when it's idling you should have close to 13 and revving it up to 1000 RPM or so it should go to 14.2 or so.

[jlwdvm]

The power going to my pertronix comes from a wire that is spliced to the resistor wire that comes out of the junction box on the firewall. I cut the resistor wire as close to the firewall that I could get in an attempt to get the motor to fire faster after starting to crank. I still have to let it crank for a few seconds or leave the key in the on position while I am putting my safety belt on and then it fires right up. Can I attach my volt meter to the red wire going into the distrubutor into the pertronix?

[torqhead]

Originally Posted by jlwdvm

The power going to my pertronix comes from a wire that is spliced to the resistor wire that comes out of the junction box on the firewall. I cut the resistor wire as close to the firewall that I could get in an attempt to get the motor to fire faster after starting to crank. I still have to let it crank for a few seconds or leave the key in the on position while I am putting my safety belt on and then it fires right up. Can I attach my volt meter to the red wire going into the distrubutor into the pertronix?

Yeah, you could do that. Personally I would put a relay in to ensure you've got good power there. Has this worked right before? Did this just start happening? What's your charging system read at the battery?

["QUICK-SILVER"]

Pertronix Ignitor PN 1181, uses OE resistor power to coil (+). Ignitor red wire gets non resisted battery power from ignition switch.

You need to get an old distributor cap and set of wires, something you can tear up.
Cut a hole in the cap under a plug terminal, pick one where you can see the rotor button easy. Paint a good white mark right in the middle of the rotor button, so you can see it easy through the hole you cut. Then watch it with your timing light.
This is how you check rotor phasing, where the button is actually pointing when the coil fires.
Doing this you'll be able to see if the advance springs are the problem, button moving back and forth. OR
If it's the ignitor, or something electrical causing timing trouble, mark on the button will stay in the same spot.

[jlwdvm]

I didn't have the timing issues with the same distributor, battery (new), and pertronix. So if I have a good 13 volts going into the pertrinox do we have it narrowed down to a bad pertronix unit or a bad advance weight spring? Do I test for the 13 volts while motor is running or key just in "on" position? Thanks.

["QUICK-SILVER"]

Switch power, setting still, should be battery voltage. When you crank it, you should have higher voltage because the alternator is charging.

[jlwdvm]

What if the battery checks out good (it is only a few months old), alternator is a couple years old, no charging or cranking problems and I still don't have 13 volts going into the pertronix? If there is good voltage going into the pertronix is it toast? No missing at higher rpms while driving.

[torqhead]

Originally Posted by jlwdvm

I didn't have the timing issues with the same distributor, battery (new), and pertronix. So if I have a good 13 volts going into the pertrinox do we have it narrowed down to a bad pertronix unit or a bad advance weight spring? Do I test for the 13 volts while motor is running or key just in "on" position? Thanks.

So if this worked correctly before and all of a sudden this started happening I would start with the very basics, lets make sure you've got good power.

Just check voltage at the battery, see what the voltage is before you start the car, probably will read 12 point something, then start it and make sure you have around 13v at idle. It should be slightly higher then what the battery read before you started the car and when you rev it slightly as I suggested before watch the voltage and see if it goes to 14+. If you do not have a slightly higher reading after you start the car and when you rev it up it charges or doesn't charge you've got a charging problem and that's what's more then likely causing your problem.

[torqhead]

Originally Posted by jlwdvm

What if the battery checks out good (it is only a few months old), alternator is a couple years old, no charging or cranking problems and I still don't have 13 volts going into the pertronix? If there is good voltage going into the pertronix is it toast? No missing at higher rpms while driving.

From this description I would guess your charging system is working up above idle, still check the idle state.

[torqhead]

Originally Posted by "QUICK-SILVER"

Switch power, setting still, should be battery voltage. When you crank it, you should have higher voltage because the alternator is charging.

I'm going to have to pull this test.... I would think while cranking that the load of turning the motor would actually drop the voltage.

["QUICK-SILVER"]

Pertronix Ignitor PN 1181;
Operating voltage: 8 to 16 volts DC, will also work with some 6 volt systems.


Posted the only way I know how to find out for sure where the problem is.

[torqhead]

Originally Posted by "QUICK-SILVER"

Pertronix Ignitor PN 1181;
Operating voltage: 8 to 16 volts DC, will also work with some 6 volt systems.


Posted the only way I know how to find out for sure where the problem is.

You're my idol... lol I was just trying to find the specs on that dang thing. hehe

["QUICK-SILVER"]

Originally Posted by torqhead

I'm going to have to pull this test.... I would think while cranking that the load of turning the motor would actually drop the voltage.

Yes of course it's going to drop while cranking.

You're trying to find out why the timing is jumping around.

[jlwdvm]

will run some tests and get back to you. Thanks for all the help.

["QUICK-SILVER"]

Originally Posted by torqhead

You're my idol... lol I was just trying to find the specs on that dang thing. hehe

You should see all the mess I have piled up around the computer.
Get fussed at by the better half, but she know's this is how I have fun.



Catch you guys later

[jlwdvm]

more info: Battery voltage engine off: 13.7
pertronix red lead engine off: 13.4
pertronix engin at idle: 16.53-16.8 (battery voltage the same)