Well, adjusting the distributor...

[blueroo]

didn't change my performance that much. I still get ignition breakup ( I think that's what it is) around 4K-4.5Krpm in 1st and 2nd gear. The one main difference is my fuel economy. It dropped hard. Without changing my driving style, I've used roughly three quarters of a tank in three days...a lot more than gas than usual.

Can anyone think of why I'm getting breakup in first and second gear around 4K while rolling yet I can rev to 5 grand in neutral without a problem?

 

[jahearne]

The diffference between 4000 when driving and 5000 in neutral is the motor is under a load when driving. That's my guess.

 

[JOHN G]

The vacuum under load vs. free-revving is different. I was getting the same type of issue and began fiddling around with the vac advance to get rid of it. You also use more fuel under load than free-revving as well. I'm actually considering going to mechanical only advance to see what it'll do.

 

[Anonymous]

Can anyone think of why I'm getting breakup in first and second gear around 4K while rolling yet I can rev to 5 grand in neutral without a problem?

Lots of possibilities
1-valve adjustment needed
2-Carb simply not big enough to support those rpm's
3-Float not high enough to support those rpm's
4-Fuel pressure not high enough to support those rpm's(lots of poss's here from dirty fual filter to stopped up tank vent line)
5-every day tune up items (wires-fuel/air filters-plug gap-point gap or tension arm. etc) not healthy enough to support those rpm's.
6-weak choke spring(if auto choke) resulting in choke closing under hi rpm suction.
7-weak or damaged vac adv diaphram.
8-throttle needs adjusting(not opening fully)
Lots more come to mind.
As has been mentioned no load and under load have very different needs. Good luck.

 

[MustangSix]

The spark energy required to initiate combustion is much higher under load than when freely reving. It's possible that what you have are wires, plugs, cap, or something else that's reduing the spark output to a level that is ineffective under load.

As the load increases, the spark will try to find an easier path to ground. That's when you'll begin to see arcing wires, caps, or coils.

Check your components carefully and replace anything remotely corroded. Change the wires and plugs.

Only after the ignition checks out, go to the carb. It might be an overly lean mixture caused by a stuck float, clogged needle or jet, or an inop power valve. But don't fiddle with that until you get the sparks right.

 

[XFlow_Fairlane]

I wish I could help you but I went to a pertronix years ago on my 170. Def look at spark though. what carb are you running? if it is a holley you might just be maxing out the carb. are your rockers lashed correctly?

 

[blueroo]

Distributor is a Pertronix Ignitor I system with the matching epoxy filled coil. Carb is a stock Autolite 1100. Plug gap is set at .044

I'm not sure if this will have a bearing on it, but after driving a while, the choke lever on the dash begins to push out.