Ignition Timing

[68/2K]

I have a 68 2000 that runs like a million bucks in the garage.
As soon as I leave the driveway and put it under a load, it spits and sputters and backfires through the carb.
The distributer has a recurve kit.
The Dwell is set at 51 deg. Timing is 16deg. Mixture set with a colortune and airflow at idle and 2500 rpm set with a Uni-syn.

Somebody had the slotted plate over the flyweights backwards. I reset that although I did notice some wear in one of the flyweight pins and wear from the ball bearings on the underside of the cam plate.

The heavy spring seemed awful loose. Not sure if its the correct spring.

Also, did I read somewhere that I need to replace my N17 needles once the recurve kit is installed in the distributer?

Any help would be greatly appreciated. She wants to be back out on the road!

SH92@Bellsouth.net

[S Allen]

You know I am going to start sounding like a broken record but I would look real hard at the ignition system. Paying special attention to the distributor and its components. The roadster dizzys were prone to wearing out the bushings providing a wobbling rotor which is not good. I had one like that and it ran like crap. Could be your points as well. I will put a shameless plug in for one of Gary Boone's most excellent EI dizzys. I run them in my Z and all of my roadsters including the race car.

As to the needles-the N17 I believe is stock. Dean of Fairlady Products carries the N25 which is said to provide more juice at the higher RPMs. Other vendors may have them as well.

Many people blame problems on the carbs but if it was running fine before and started running crappy out of the blue I would suspect the ignition system. The SUs are pretty rock solid except for the rare stuck valve or leaky float.

I am sure others will have more input for you but that is my 3 cent guess.

Steve

[TR]

The timing:

Check the timing through the RPM range in the driveway with the vacuum advance disconnected and plugged. Ensure you get the amount of advance your kit specifies. It should set in smoothly and stay steady once you get to 2500-3000RPM. Check it again with the vacuum advance connected and ensure you get all of the advance smoothly. I assume your kit is the 7.5 degree kit and your vacuum should be 10 degrees, so you should get a total of about 33 degrees. This might be a bit much for a tired engine, you may try backing the idle down a few degrees, especially if the spitting starts around 2500-3000RPM.

Fuel (Assuming SU's):

If it doesn't start to act up until after some driving time, it could be a fuel issue. Weak pump, clogged line, filter(s), etc. One quick test is to disconnect the float overflow line from the intake filter box. Jump a piece of tubing to the two ports on the box, and another between the two connections on the float bowl covers. Alleviating this vacuum (compounded by a dirty filter) sometimes gets a car with issues over the hump. If this does make the car perform better, investigate everything that touches fuel...

Good luck and get her out there for Spring! TR