Anti-surging

[hkestes41]

I have been having an issue the past week or so when I drive at highway speeds. After running for about 15 miles at 65 mph or so, the car starts to lose power and begins to kind of anti-surge for lack of a better term. In other words there is an intermittent loss of power, kind of like surging but the opposite. If I slow down and drive on the surface streets the problem seems to go away and I can drive on to my destination.

I thought I may have a slightly "clogged" gas cap causing a vacumn to pull on the tank at the higher speeds. So, last night I pulled the cap off completely and drove home without it. Again about 15 miles and it starts anti-surging. The rubber portion of the fuel line along the front crossmember is new so I don't think it is collapsing but I am not positive. Don't know how I would check for that since the problem goes away when I slow down.

Now I am wondering if it is maybe the coil, (I am running the Langdon HEI and coil). If it is the coil should I expect the problem at any speed or would it be more prevalent at higher speeds?

Any other suggestions?

[DutchEdwin]

I had a car once that had the same problem. As I drove it would suddenly lack power. It turned out that the carb was contaminated inside behind the needles. Cleaning out the carb solved the problem.

Hack, this was my first problem, on my girlfriends car as I didn't own one, it took me 1 month to discover the problem. Got me into a new hobby CARS

[Jim Saraceno]

I also had a similar problem and it also turned out to be a fuel line clog.

You may want to give the fuel pump a volume and pressure test.

[greg g]

Wonder if you have a vacuum leak somewhere between the carbs and the engine that is causing the misture to lean out when stuff gets hot. Can you rig a vacuum gauge so you can read it when the problem exists?

Make sure all you nuts and bolst are good and snug from the carb bases to the block.

The other thing you might check is the internal screen in the fuel pump. It will sometimes get clogged or get enough stuff on it to restrict fuel flow at high demand.

You can access this by removing the center bolt on the inlet chamber fo the pump. Also make sure there is no debris within this hollow bolt.

The fuel flow test should give you 8 to 10 ounces of fuel based on 12 pump cycles.

[Plymouthy Adams]

did you try to enrichen the mixture by pulling the choke out a tad to clear this surging..