Ignition Timing Check

I tested my ignition advance on Saturday morning. To test it, I removed the vacuum tube from the distributor and plugged it with a golf tee. I then used a timing light to check the base advance and the mechanical advance at a few RPM points. I recorded the following:

850 - 11 Degrees BTDC
1000 - 11 Degrees BTDC
1500 - 15 Degrees BTDC
2000 - 23 Degrees BTDC
2500 - 29 Degrees BTDC
3000 - 36 Degrees BTDC

With an initial timing of 11 degrees and the 15 degree plate in the distributor, my total advance should be 41 degrees. I did not check the advance at 3500 RPM but I'm sure all 41 degrees is present by that point.

To get better performance, I could replace the other stiff, stock spring with the light version I received in the kit. This would provide all the advance by around 2800. Since I cannot change my vacuum advance settings, I'm concerned this could result in pinging which I would not be able to correct. Since this works well, I will leave it alone for now.

Carburetor Tuning Continued

I called O'Reilly from work yesterday and they said they could get the Holley pump cams by 5 o'clock. I ordered them and paid a premium price ($27.99). However, I would have paid the same to get the from Summit after the shipping cost.

I put on the new coil this morning and the new spark plug wires. I then switched from the stock orange pump cam to use the new size up which is black. I then checked the front float level and found it is not set as high as I remember. I raised the front float level and then took the car for a drive.

The hesitation on accelration if fixed. It seems there is a small hesitation at very low RPM. This is likely because the idle mixture is off or because I could function with the orange cam with the raised float level. I'll fine tune it later. For now, I'm just happy the drivability is much better.

The current setup is shown below.

Carburetor Tuning Continued

I received the new distributor springs, Petronix FlameThrower Coil, and MSD Street Fire spark plug wires in the mail today. The springs are rated to deliver full mechanical advance by 2,400-2,800 RPM. I was concerned that would be too quick so I used one and one of the stock springs.

I drove the car around tonight with only the new spring installed. This seemed to help low RPM performance some but did not fix the hesitation. I posted on a few Mustang forums to get some additional help with the problem. The only response so far requests I try new pump cams.

Ignition System Upgrade

I removed the distributor cap and top plate today. I wanted to check the internal parts to determine how much mechanical advance was possible. I found a 15 degree arm installed which would provide 30 degrees over the base timing.

The RPM at which the timing increases is controlled by two springs. The stiffer of the two springs was stretched and did not fit properly on the mounting points. The other spring fit well but had less resistance. I'm going to replace these springs while I have the distributor apart. The new springs should allow for full advance by 2800 RPM.

I tried to locate new springs all over the city but no one sells them. I ordered them from Summit with a new coil and some spark plug wires. They should arrive by Friday and I'll install the parts this weekend.

I hope the additional advance corrects the hesitation I feel when accelerating.

Carburetor Tuning... Still

I've tried numerous different things to get rid of the hesitation on acceleration. I've tried new accelerator pump nozzles, changed the pump cam position, and changed secondary springs. Unfortunately, none of the combinations of things I've tried have fixed the problem.

I removed the spacer today. The spacer should add power but can move it up the power band and create a lean condition. I was not sure this would make much of a difference but it was worth an attempt. I found the hesitation remains but seems to disappear at high RPM (over 2500).

I've asked on the VMF about the situation and I've received a variety of responses. Several suggested new jets, others said new pump cams, and others have questioned the timing. It is unfortunate so many things can cause the same type situation.

I'm going to expore the timing next as I think I've eliminated many of the carburetor variables as being the entire cause. I took the distribution apart and found 15 degree plates. One spring was very tight and the other is soo lose it could fall off. I think I try to find some at a local auto parts store and then check my mechanical advance with a timing light.