Here is the equipment scoop:
Engine is a 12A Streetported Rx7 motor with a Racing Beat/Holley 465CFM carburator and Racing Beat intake manifold. Engine has Electronic Ignition Distributor, and is firing from two MSD Blaster 2 coils. I initially had a problem with the trailing plugs not firing, but realized that my tachometer wire had a short somewhere, so when removing from coil connection, all firing was fixed. All timing on the ignition has been set correctly, and is firing per the marks on the pulley with proper advancement. I have checked the fuel pressure to the carburator, and I am maintaining 6psi even under high RPM load.
Here are the symptoms:
Car starts perfectly fine and idles as it should. Once placed into gear and I begin to take off, the car hits between 1500 - 2500 RPM and it's like the bottom falls out from it. There is a massive flat spot where the engine simply spudders and acts like it is going to die. During this time, the car is in motion, but because it seems like it is fighting for fuel, it jerks forward and backward fairly violently. At this point you either need to let off on the throttle to get it to calm down, or apply a pretty stout foot into the throttle to force it past this stage, at which the car will immediately take off quite briskly. At any given gear, this RPM range is the primary cruising range for the motor, so you can never just drive at a given speed. You either need to be into the throttle at this range, or out of the throttle to keep the motor going. Very frustrating, as this was a professionally built motor, and I feel I have chosen intake equipment with a proven track-record, but something has definately gone wrong in the process.
I did a little bit more research on the issue, and I agree, it is not the power valve. At this point, I am at a loss, as I simply do not know that much about carburators. It's quite the shame, as I did take the car out over the weekend amidst all the problems, and was accosted by two different gentleman that were in awe of seeing an RX2 on the road. Both had identical stories to mine regarding their passion for old RX2's and RX3's, but with the difference being that they let theirs go when they were younger. I chose to keep mine, and I want to get it on the road consistently, so that others can appreciate it as much as I do.
Any thoughts appreciated!
Pictures of car are on page 3 of "1973 Mazda Rx2- Return from the dead project" in this same section - Mazda Garage.
Take a look if you are interested!