Tuning problem with my Nailhead

I have been trying to sort out a tuning problem as I get my coupe ready for the trip to Austin for the Roundup. The thing runs fine under power or at idle. But rolling down the road at a steady speed it misfires enough to- I'll call it "fluttering". Not a distinct misfire, but just not quite firing right. As soon as I give it just a little throttle it is fine.
It is a stock point distributor, dual AFB carbs that were working fine last trip I made in it and they have not been touched. Any ideas out there? I have changed points and condenser (twice actually),cap and rotor, recently put a new coil and ballast resistor on it. Any help appreciated.
Rodshop

 

No ideas fella's?

Rodshop

 

Is it surging like its lean?

 

No I don't think that is it. I had the carbs working well last summer and nothing has changed with them so I don't think it is lean. it is not totally misfiring but it is not hitting right either until it is under even a little acceleration. Then it is fine. What would make if fire poorly at a cruise speed?
Rodshop

 

How do you have it timed? Also, were you burning up points even with a resistor? (you mentioned you changed the points twice).

 

I swapped out the points & coil on '56 322 recently to the Pertronix conversion and it was a big improvement. Starts quicker, runs better, improved throttle responce, much less popping on decel (I run open headers)... basically an all around better running engine now. However, mine never really ran poorly with the points and it didn't eat em either. In the 9 years I have had my roadster on the road, I have only put one set of points and a coil in it when I first got er running. I was so impressed with the Pertronix stuff, I bought another set for my 55 Special.

 

I only changed the points twice just in case I got a bad set- but superchargednailhead got me going down the right road. It was too lean and with a couple of changes of metering rods on the way down to the Roundup I pretty much have it worked out. What I can't figure out is what would have made it run OK last year and now it needs to be richer?????? anybody know why that would happen?

Thanks for the hlep guys. Austin is great!
Rodshop

 

One way to help narrow down possible causes is to clean the plugs up good and take it for a spin and let it misfire or "flutter" for a good bit and then shut it off immediately and pull over and check the plugs. That way you can determine if it's a lean or rich problem...

 

I would consider a sloppy timing chain.A little power and it takes up the slack.

 

id agree with lean possibly partially blocked jet from somthing that got by the fuel filter.