Gator
Well-Known Member
I'm looking for a quality brand of spark plug wires to run with headers looking for some suggestions
...but I'm trying to tune my Thermoquad.I just rebuilt it.I'm getting a little bit of a backfire and hesitation not all the time ...
I would think the chrome box is a little to much for a street driven car. Im sure someone else might chime in.It's not lean burn.have mopar chrome box mopar distributor,1 I don't now how to adjust the secondary air valve tension.I think it runs pretty decent other wise
...The infamous "ThermoBog" is usually caused by air doors that are too tight rather than loose (it's a lean condition, not an actual bog)...
Without getting into too much into wall-wetting (X/Tau) discussions...
When you're cruising along at part throttle, you're under vacuum due to both the venturi effect on which carbs operate, and the restriction of the partially-closed throttle plate. Stabbing the throttle opens the primaries wide, as well as the secondary throttle plates. The accelerator pump's function is to give an extra fuel shot to the new influx of air, but it's only enough to cover it for a very short amount of time. This is why the car surges for a split second before the hesitation. On the secondary side, even though the throttle plates are open, the air doors aren't. Since the air doors aren't perfectly sealed like throttle blades, air gets past the various gaps in them. Until the air doors actually move, though, no additional fuel is added on the secondary side. There's your hesitation: the pump shot is used up, four throttle plates are wide open and moving air (only partially on the secondaries), but only two jets are moving fuel. For that moment, the engine falls on its face while it sucks accumulated fuel from the intake runners and port walls to burn with the extra air. Once it does that, it picks up speed and there's enough air speed to open the secondary air doors and metering-rod piston... and you're off like a shot. Loosening the air doors gets the party started sooner.
In reality, the accelerator pump's function is primarily to replace fuel lost from the intake runners and port walls, not to directly feed the cylinders. This is why acceleration enrichments are much trickier to get perfect on a multi-port engine: There's much less accumulated fuel to evaporate into the sudden increased airflow. There's also no venturi effect to draw additional fuel through the metering orifices, so that and the "accelerator pump" function need to be made up with increases in injector pulsewidth. Those increases need to be scaled to both the change in throttle position as determined by the sensor and change in overall load/air flow via either the manifold's absolute pressure on a speed density system, or actual measured airflow on mass-airflow systems. Better engine management systems use X/Tau calculations for acceleration enrichments, based on the evaporation rate of fuel from port walls v. airflow/manifold pressure as a function of time, rather than just sensor readings. Fun stuff.
When I'm thoroughly setting up a ThermoQuad or a Quadra-Jet, I loosen the tension enough to let the air doors open from gravity, then tighten just enough that the spring closes them (obviously, this is done with the engine off). I give it one more half-turn to tighten, secure the lockscrew, and test the car under load. Sometimes it needs to go tighter, sometimes it's good where it is, and even with it that loose I've had to loosen it a tad. As set from the factory, though, virtually every one to which I've done a "quickie" adjustment needed to be loosened.
...Until the air doors actually move, though, no additional fuel is added on the secondary side. There's your hesitation: the pump shot is used up, four throttle plates are wide open and moving air (only partially on the secondaries), but only two jets are moving fuel...
...When I'm thoroughly setting up a ThermoQuad or a Quadra-Jet, I loosen the tension enough to let the air doors open from gravity, then tighten just enough that the spring closes them (obviously, this is done with the engine off). I give it one more half-turn to tighten, secure the lockscrew, and test the car under load...
I run non-resistor wires. 7mm from packard bell, if i remember right...I'm looking for a quality brand of spark plug wires to run with headers looking for some suggestions