Timing and Dizzy Help

[srickets]

I have a 1969 Mach1 with a 351C stroker & 4 Speed Toploader.

For ignition I have an older Mallory Unilite dizzy - mechanical advance with Mallory cylindrical coil and ballast resistor.First off the car starts and runs good.

When I first start the car and let it warm up the timing is consistently at 17-19 BTDC (900 RPM). If I rev the car up to 2000 RMP it will eventually settle back to 900 RPM but the timing will now be around 23-24 BTDC, which doesn't seem correct to me. At 3000 RPM the total advance is 37. I checked the dizzy and it is securely locked down.

I decided to have a look under the cap. I checked the Unlite module and Coil out (Multi-meter) using the instructions provided by Mallory and both tested OK. I also had a look at the advance springs and noticed that one spring has no tension to it (although it is still attached to its posts).

Also, the rotor does not 'snap back' when i twist it (clockwise or counter clockwise).
There is a small amount of play (either dirction) in the rotor.

I'm not sure if I have any issues here or not.

I would greatly appreciate your comments and suggestions.

Thanks,

Scott

 

[blown65]

The mechanical advance is probably sticking or the springs are just weak causing it not to pull all the way back to the initial setting. That one loose spring is your issue.

 

[PoppyMod]

I have a 1969 Mach1 with a 351C stroker & 4 Speed Toploader.

For ignition I have an older Mallory Unilite dizzy - mechanical advance with Mallory cylindrical coil and ballast resistor.First off the car starts and runs good.

When I first start the car and let it warm up the timing is consistently at 17-19 BTDC (900 RPM). If I rev the car up to 2000 RMP it will eventually settle back to 900 RPM but the timing will now be around 23-24 BTDC, which doesn't seem correct to me. At 3000 RPM the total advance is 37. I checked the dizzy and it is securely locked down.

I decided to have a look under the cap. I checked the Unlite module and Coil out (Multi-meter) using the instructions provided by Mallory and both tested OK. I also had a look at the advance springs and noticed that one spring has no tension to it (although it is still attached to its posts).

Also, the rotor does not 'snap back' when i twist it (clockwise or counter clockwise).
There is a small amount of play (either dirction) in the rotor.

I'm not sure if I have any issues here or not.

I would greatly appreciate your comments and suggestions.

Thanks,

Scott

Hi Scott,
I would have the dizzy re-curved to a spec that pulls in all of your advance by 3K, or so. I had my done and was very happy with the work. Also, the shop will provide you complete specs of when the advance is occurring. Then you'll know. If you don't have a shop, I know one in Michigan that will do the work and is not expensive. If you want more details, PM. I'm not sure of the policy here on vendor recommendations. Also, you'll know how much mechanical is built in, which, I think is 24 degrees.
Good Luck1

 

[srickets]

Hi Scott,
I would have the dizzy re-curved to a spec that pulls in all of your advance by 3K, or so. I had my done and was very happy with the work. Also, the shop will provide you complete specs of when the advance is occurring. Then you'll know. If you don't have a shop, I know one in Michigan that will do the work and is not expensive. If you want more details, PM. I'm not sure of the policy here on vendor recommendations. Also, you'll know how much mechanical is built in, which, I think is 24 degrees.
Good Luck1

Thanks for the info PoppyMod.

I'll check for a local vendor and if I don't come up with one I'll PM you.

I hope you have a Merry Christmas.

 

[srickets]

The mechanical advance is probably sticking or the springs are just weak causing it not to pull all the way back to the initial setting. That one loose spring is your issue.

Much appreciated blown65.

Have a Merry Christmas.

 

[horseballz]

Not unusual for Mallory distributors to have one loose spring. Read this for a general idea:

http://www.malloryperformance.com/pdf/29014.pdf


Not necessarily for your particular unit, you need to determine which of several advance setups you have.
My $.02,
Gene

 

[rehood]

Timing...

I have a 351 C with an ignition like yours. I also had the same issue. Turned out to be too much end play in the distributor shaft. The driven gear ( on the shaft ) would ride up on the cam gear and change the timing. It would settle down if you pop the accelerator, but it would stay advanced if you just drove normally. It also wore out the distributor shaft bushings along the way. That shelf clerance is a huge issue and I'll bet the source of your problem

 

[srickets]

Not unusual for Mallory distributors to have one loose spring. Read this for a general idea:

http://www.malloryperformance.com/pdf/29014.pdf


Not necessarily for your particular unit, you need to determine which of several advance setups you have.
My $.02,
Gene

Interesting. I'll check the springs and plot out my current curve and see what I get.

Thanks,

Scott

 

[srickets]

I have a 351 C with an ignition like yours. I also had the same issue. Turned out to be too much end play in the distributor shaft. The driven gear ( on the shaft ) would ride up on the cam gear and change the timing. It would settle down if you pop the accelerator, but it would stay advanced if you just drove normally. It also wore out the distributor shaft bushings along the way. That shelf clerance is a huge issue and I'll bet the source of your problem

Thanks Redhood.

I'll pull the distributor and inspect it.

What should I look for to confirm the scenario you described?